These are organizations that span that gray area between civilian law enforcement and the military. Much like the US Coast Guard. The Coast Guard is not a purely military force like the Navy, nor is it a civilian law enforcement agency like a transportation police. It performs some customs and security duties, but also does search and rescue functions plus environmental protection.
Arguably the proper term is "quasi-military".
According to Snopes.com:
If a spacecraft is flying far away from anything else, and only has weak rockets fueled by puny chemical fuels or innocuous solar panels, nobody cares if the ship is a hunk-of-junk suffering from decades of deferred maintenance. If it blows up, that's too bad about the people on board, but it's their problem.
Things change radically in the more civilized areas of space. In the crowded orbital space around a heavily populated planet, with dozens of space stations, zillions of expensive satellites, hundreds of other spacecraft in tight traffic lanes, and ship using antimatter fuel; the authorities will demand that all spacecraft be up to code with perfect maintenance records.
This means periodic inspections by the Spacecraft Agency, in order for the ships to keep their certification current. No certification means the ship ain't allowed in our orbital space.
For example, in the US, this is the responsibility of the Federal Aviation Administration's Aviation Safety Inspectors. They inspect aircraft and related equipment for airworthiness. They are a Designated Airworthiness Representative (DAR), appointed in accordance with 14 CFR 183.33 who may perform examination, inspection, and testing services necessary to the issuance of certificates. There are two types of DARs: manufacturing, and maintenance. The maintenance type are the ones inspecting aircraft.
The manufacturing type inspect the aircraft before it is even made. Aircraft require a type certificate to signify the airworthiness of an aircraft manufacturing design. This means it is almost impossible to certify an aircraft built from blueprints that lack a type certificate. Or built from no blueprints at all.
All vehicles will have something answering to a unique vehicle identification number.
Each vehicle needs to be uniquely identifiable. Why? Quite a few good reasons:
- Liability Insurance (if the vehicle damages something or somebody)
- Vehicle Insurance (if the vehicle suffers damage and needs repair)
- Theft Insurance (if the vehicle is stolen)
- If the vehicle was purchased by an installment loan
- Vehicle Registration
- Contracts (e.g., according to contract semi-trailer truck XYZ must be at location Alfa at twenty hundred hours to be loaded with cargo Bravo and transport it to location Charlie)
For these and other expensive issues you must be able to unambiguously identify the vehicle being referred to in the legal documents.
Ordinarily this is a straightforward process. But things get sticky in a rocketpunk future containing modular spacecraft with parts you can change as easily as Lego. Swap a few parts and you suddenly have a legal Ship of Theseus paradox on your hands.
To operate said vehicle within national boundaries, the vehicle will have to be registered with the nation's official vehicle bureau (including passing the minimum functional and maintenance requirements, and paying the registration fee ). Some sort of vehicle registration plate(s) will be issued displaying to the authorities the registration number associated with that vehicle and the vehicle's identification number. Anybody who has purchased an automobile is familiar with the concept.
Instead of a automobile registration plate, spacecraft will probably have some kind of Automatic Identification System (the thing that the Traveller RPG mistakenly calls a starship's transponder). In addition to being used by law enforcement and the military, this will probably also be required by space traffic control.
Registration of spacecraft actually exists in the real world: the 1974 Convention on the Registration of Objects Launched into Outer Space. However, the transparency of the registration is often subverted. Specifically there are satellites orbiting Terra that are pretty obviously military in nature but there is not a hint of this mentioned in the registration. See Critical issues related to registration of space objects and transparency of space activities (updated list of unregistered satellites).
A commercial spacecraft, unlike an automobile, has issues similar to a commercial cargo boat. So they too may seek to avoid certain legal and taxation entanglements by using a questionable "flag of convenience". Occasionally this tactic can backfire with catastrophic results for the corporations that own the vessels.
This is more or less the space-going version of the Coast Guard. They are not military so much as they are a cross between a law enforcement agency and a search and rescue body. A real world organization that does straddle the line between military and civilian is the United States Air Force Pararescue
Orbit Guard assets tasked with SAR duties will require specialized space rescue equipment.
Since the Coast Guard operates in the coast, the Orbit Guard operates within the Hill Sphere of inhabited planets. Using the analogy that planets are islands and deep space is the ocean, Orbit Guard spacecraft can be called "Littoral".
Though the question of territory is a bit unsettled. A boat in the coast of Great Britain is stationary around Britain. But an orbital spacecraft constantly moves in its orbit around Terra, passing over many different continental nations on its ground-track. This isn't a problem if the entire planet is under one government, only if it is balkanized.
There is no hard and fast division between the Orbit Guard and the Patrol. They sort of blur into each other. In some cases they might merge into one organization. The Orbit Guard is more biased to the civilian/search-and-rescue end of the spectrum, while the Patrol is biased more to the military/pirate-hunting end of the spectrum.
Yes, I originally used the term "Orbit Guard" for those tasked with preventing asteroid bombardment warfare. I changed it for reasons explained here.
Orbital Patrol Ship Stats Propulsion Chemical
Exhaust Velocity 4,400 m/s Specific Impulse 449 s Thrust 3.5×106 N Thrust Power 7.7 gigawatts Total ΔV 6,100 m/s Mass Budget Engine Mass 7 mton Heat Shield Mass 15 mton
(15% re-entry mass)
(5% landing mass)
(5% landing mass)
(20% dry mass)
(5% dry m)
Tankage body 18 mton
INERT MASS 75 mton Payload,
25 mton DRY MASS 100 mton Propellant
300 mton WET MASS 400 mton Mass Ratio 4.0 Plus
This is a splendid spacecraft designed by Rick Robinson, appearing on his must-read blog Rocketpunk Manifesto. This was designed for his Orbital Patrol service, which he covered in three previous posts.
The important insight he noted was that if you can somehow get your spacecraft into orbit with a full load of fuel/propellant, it turns out that most cis-Lunar and Mars missions have delta V requirements well within the ability of weak chemical rockets. So you make a small chemical rocket and lob it into orbit with a huge booster rocket (heavy lift launch stack). This will be the standard Orbit Patrol ship.
It can also be boosted into orbit by a smaller booster rocket, then using the patrol ship's engines for the second stage. So as not to cut into the ship's mission delta V, it will need access to an orbital propellant depot to refuel. At a rough guess, you'll need 9,700 m/s delta V to boost the patrol ship into orbit (7,900 m/s orbital velocity plus gravity and aerodynamic drag losses). So the booster will need 9,700 m/s with a payload of 400 metric tons. Bonus points if the booster is reusable.
Actually, it reminds me a bit of the old Three Man Space Scout.
At a rough guess, Rick figures that if the ship is capsule shaped it will be about 12 meters high by 14 meters in diameter. If it is wedge shaped, it will be about 40 meters high by 25 meters wide by 8 meters deep.
In both cases, total interior volume of 1,200 m3 (of which 900 m3 is propellant), and a surface area of 800 m2
Present day expandable propellant tanks have a mass of about 6% of the mass of the liquid propellant. Rick is assuming that in the future the 6% figure will apply to reusable tanks as well.
If my slide rule is not lying to me, the 300 metric tons of H2-O2 fuel/propellant represents 33.3 metric tons of liquid hydrogen and 266.7 metric tons of liquid oxygen. About 470 m3 of liquid hydrogen volume (sphere with radius of 4.8 m) and 234 m3 of liquid oxygen volume (sphere with radius of 3.8 m). This is a total volume of 704 m3 which falls short of Rick's estimate of 900 m3 so I probably made a mistake somewhere.
Landing on Terra will use retro-rockets, the heat shield for aerocapture, maybe a parachute, and aircraft style landing gear for belly landing. Landing on Luna or Mars will be by tail-landing on rear mounted landing legs. That will also mean reserving some of the propellant for landing purposes.
Note that the heat shield is rated for the ship's unfueled mass (heat shield mass = 15% of ship's re-entry mass), there is not enough to brake the ship if it has propellant left. This assumes a "low-high'low" mission profile: start at LEO, go outward to perform mission while burning most of the propellant, then return to LEO or even land on Terra. So 15 metric tons for heat shield is for a ship with a mass of 100 metric tons at re-entry (ship's total dry mass).
If the ship is going to aerobrake then return to higher orbit, it will need more heat shield mass to handle the extra mass of get-home propellant. This will savagely cut into the payload mass, which is only 25 metric tons at best. For example, if the mission had the ship heading for translunar space from LEO after aerobraking, the extra propellant mass at aerobrake time will increase the heat shield mass from 15 metric tons to 31. This will reduce the payload from 25 metric tons to 8. But by the same token a ship that will not perform any aerobraking can omit the heat shield entirely, using the extra 15 metric tons for more propellant or payload.
Payload includes habitat module (if any) as well as cargo, since hab modules are optional for short missions. The gross payload is 25 metric tons, of which 20 is cargo and the other 5 mtons are payload bay structure and fittings. If you assume two tons of life support consumables per crew per two week mission; then the ship could carry a crew of five plus 12 mtons of removable payload, or a crew of 10 and 4 mtons of payload (the more that payload is consumables, the less mass needed for payload bay structure).
Patrol Missions Mission Delta V Low earth orbit (LEO) to geosynch and return 5700 m/s powered
(plus 2500 m/s aerobraking)
LEO to lunar surface (one way) 5500 m/s
LEO to lunar L4/L5 and return
4800 m/s powered
(plus 3200 m/s aerobraking)
LEO to low lunar orbit and return 4600 m/s powered
(plus 3200 m/s aerobraking)
Geosynch to low lunar orbit and return
Lunar orbit to lunar surface and return 3200 m/s
LEO inclination change by 40 deg
LEO to circle the Moon and return retrograde
3200 m/s powered
(plus 3200 m/s aerobraking)
Mars surface to Deimos (one way) 6000 m/s
LEO to low Mars orbit (LMO) and return 6100 m/s powered
(plus 5500 m/s aerobraking)
For a representative samples of small space craft atop booster rockets go here.
All that junk in Terra orbit could trigger the dreaded Kessler Syndrome. If it happens, mankind might be cut off from space for generations. The Orbital Debris Collection agency is tasked with preventing that unhappy state of affairs.
The Kessler syndrome (aka Kessler Effect, Collisional Cascading, or Ablation Cascade) is where the number of pieces of orbiting space trash becomes so high that a single collision can start a chain reaction. A collision turns two pieces of trash into twenty. Most of those twenty new pieces will suffer collisions, now you have 400. When those hit you'll have 8,000. A couple of more collision cycles and LEO will basically become impassable. No more space launches, no more astronauts, no more GPS, no more communication satellites, no more space station.
If it actually happens space exploration and even the use of satellites could be rendered impossible for many generations. Egads.
The cascade may not spread to geostationary orbit, but that will just slightly delay matters. As those satellites wear out, they cannot be replaced.
A fictionalized version of this was depicted in the movie Gravity. It was exaggerated for dramatic effect, but not by much.
Note that this will probably be only an issue in Terra (or alien homeworld) orbit for hundreds of years to come. Other planets will need that long before enough trash collects in their orbit to become a problem.
Since the Kessler Syndrome could deny access to space for generations, it is logical to establish a (preferably multinational) organization charged with cleaning up orbital debris. But never underestimate the power of human stupidity.
Since politicians in general care little for anything happening beyond the next election cycle, they probably have little appetite for the money and poltical capital which must be spent to establish such an organization. Much like Spaceguard, actually. Action will probably be triggered by a close call or two.
And much like the manga Planetes the members of the serivce will be denigrated as "janitors" and "trash collectors".
Maybe after a partial Kessler the people (and corporations who suffer savage losses to their quarterly profits) will wake up and push for an orbital debris collection agency with teeth. Nations who recklessly launch rockets into risky trajectories will be hit with punishing sanctions. Or hit with an ODC commando team capturing the launch facilities.
And terrorists attempting to initiate a Kessler event will be a top-priority item with the counter-terrorism agencies of the world's nations. Classification: Hostis humani generis (Latin for "enemy of mankind"). Planetes had the The Space Defense Front, a terrorist organization that believes mankind is exploiting space without first curing global problems such as mass famine and the widened socio-economic divide on Earth.
In our current day and age, people are not allowed to pilot an aircraft without a pilot's license or certification. Obtaining a license involves written tests and passing a flying test. In the United States, pilots are certified, not licensed. The difference is that legally a certification can be revoked by administrative action, while a license can only be revoked by the judiciary system (translation: the Civilian Aviation Authority can revoke a pilot's certification for whatever reason it wants, while a driver's license can only be revoked in traffic court).
Types of aviation pilot certifications include Student, Sport, Recreational, Private, Commercial, Flight Instructor, and Airline Transport. These can also be futher broken down into Category (aircraft, glider, lighter-than-air, etc.), Class (single-engine, multi-engine, helicopter, etc.), and Type (turbojet-powered, high-performance, complex, high-altitude, etc.)
Since spacecraft are far more expensive and potentially destructive than aircraft, you can be sure that space pilot certification (a "space rating") will be much harder to get. Initially such certification will be unavailable outside of the military or civilian space agencies. Once the technology has matured you will start to see commercial certification. Much later the technology will become commonplace enough to allow sport and recreational spaceflight.
In science fiction, space pilots sometime merge into a sort of guild. As time goes by it often becomes more and more difficult to join the guild unless you have a powerful guildmember as a sponsor. Eventually the guild become hereditary, where you cannot join unless one of your parents are already guild members. If things get really out of hand the guild becomes an empire and you have a full fledged Thalassocracy on your hands.
There are some science fiction novels where the pilot is not just the pilot, but also somehow a vital part of a starship's faster-than-light propulsion. These are also commonly part of a spacer's guild. Almost all of these have the pilot using some species of mystical psionic power that cannot be reproduced in a machine because of Authorial Fiat. Examples include the guild from Frank Herbert's Dune novels, "Pushers" from Robet Sheckley's Specialist, Telesthetic women from Redmond Simonsen's StarForce Alpha Centauri wargame, and Psi Navigators of the Universe RPG.
Sometimes you see a more mild application of superior abilities in humans compared to machines, milder than the human actually being the FTL drive that is. This is usually an authors device to justify the existence of human pilots, instead of a boring driverless spacecraft run by a computer autopilot. Examples include the Mass Sensor (unusable by computers) in Larry Niven's The Borderland of Sol and the Temporal Imbalance Sensor in the computer game Quest of the Space Beagle.
On Terra, there exist organizations called "Maritime militias". These are commercial merchant vessels that can be called in times of emergency into support roles. Meaning law enforcement, disaster relief, and quasi-military operations.
This would be attractive in the early years of human expansion into the solar system since no nation is going to like the idea of the insane construction and support expense of a purely military spacecraft. Especially since for the most part it will standing idle.
On Terra, though, many are troubled by China's maritime militia, aka "a covert naval fleet disguised as fishing boats, with plausible deniability." This may become even more of a problem when China expands into space.
There is no hard and fast division between the Orbit Guard and the Patrol. They sort of blur into each other. In some cases they might merge into one organization. The Orbit Guard is more biased to the civilian/search-and-rescue end of the spectrum, while the Patrol is biased more to the military/pirate-hunting end of the spectrum.
In the realm of science fiction, the Patrol was created by many authors. But the most well developed was in the space operas of Andre Norton. Norton's Patrol is right in the gray area between civilian and military, a combination of the police and the space navy. They appear in Star Rangers, the Jern Murdoc series, Star Hunter, and the Solar Queen series.
In James White's Sector General series, the Monitor Corps is strictly a police force, not a military one. White put it this way: if involved in a war situation the Monitor Corps are fighting to stop the war, rather than win it. To White, this is the difference between maintaining the peace and waging a war.
In the early days, at least, the Patrol may find itself performing small tasks that are not technically part of its charter. White's Monitor Corps is also in charge of interstellar survey, and first-contact work.
I wasn't sure how to logically justify such an organization, but Rob Garitta has a brilliant solution in his essay below:
Yes, the Patrol will sometimes have to do naval boarding in the discharge of their duties.
Payload Crew 25 Hab Module 100 tons Consumables 25 tons Other Payload 75 tons Total Payload 200 tons Propulsion Bus Engine+Radiator 200 tons Tankages+Keel 100 tons Stats Dry Mass 475 tons Loaded Mass 500 tons Propellant Mass 500 tons Wet Mass 1000 tons
The discussion thread about 'Industrial Scale of Space' veered, among other things, into a discussion of patrol missions in space. My first reaction was that (so long as you aren't dealing with an interstellar setting) there is no place in space for wartime patrol missions. But the matter might be more complicated, and for story purposes probably should be.
According to The Free Dictionary, patrol is The act of moving about an area especially by an authorized and trained person or group, for purposes of observation, inspection, or security. This fits my own sense of the word, and is in fact a bit broader, 'security' including SSBN patrols, which are not observing or inspecting anything, just waiting for a launch order if it comes.
In a reductionist way you could say that all military spacecraft are on patrol, since they are all on orbit, and if they are orbiting a planet they have a very regular 'patrol area.' But this is not what most of us have in mind. We picture a patrol making a sweep through an area, looking for anything unusual, ready to engage any enemy they encounter, or report it and shadow it if they cannot engage it.
Back in the rocketpunk era it was plausible that, say, Earth might send a patrol past Ceres to see if the Martians had established a secret base there. But (alas!) telescopes 'patrolling' from Earth orbit can easily observe the large scale logistics traffic involved in establishing a base; watch it depart Mars and track it to Ceres. If you want a closer look you can send a robotic spy probe. If you engage in 'reconnaissance in force' by attacking Ceres, that is a task force, not a patrol.
In an all out interplanetary war there may be plenty of uncertainty on both sides, but very little of it can be resolved by sending out patrols.
But of course all-out war is not the context in which the Space Patrol became familiar. I associate it with Heinlein's Patrol; apparently the 1950s TV series had an independent origin (unlike Tom Corbett, who was Heinlein's unacknowledged literary child).
The rocketpunk-era Patrol, which in turn gave us Starfleet, was placed in the distinctly midcentury future setting of a Federation. This is as zeerust as monorails. But plausible patrolling is not confined to Federation settings. It can justified in practically any situation but all out war.
Orbital patrol in Earth orbital space will surely be the first space patrol, and could be imagined in this century. It might initially be a general emergency response force, because travel times in Earth orbital space are short enough for classical rescue missions. On the interplanetary scale, with travel times of weeks or more likely months, rescue is rarely possible. But eventually power players will want some kind of police presence or flag showing in deep space.
As so often in these discussions, I picture a complex and ambiguous environment in which policing, diplomacy, and sometimes low level conflict blur together. To take again our Earth-Mars-Ceres example, there are kinds of reconnaissance that cannot be carried out by robots (short of high level AIs). If Ceres closes its airlocks to liberty parties from a visiting Earth patrol ship, that conveys some important intelligence information.
The ships that perform these missions will be fairly large (and expensive). They must carry a hab pod providing prolonged life support for a significant crew: at least a commander and staff, SWAT team of espatiers, and some support for both.
Let us say a crew of 25—which is cutting the human presence very fine. Now we can venture a mass estimate. Allow 100 tons for the hab compartment plus 25 tons for crew and stores plus 75 tons other payload, for a total payload of 200 tons. Let the drive bus be 200 tons for the drive, including radiators, and 100 tons for tankage, keel, and sundry equipment.
Our patrol ship with a crew of 25 thus has a dry mass of 475 tons, mass fully equipped 500 tons, plus 500 tons propellant for a full load departure mass of 1000 tons. Cost by my usual general rule is equivalent to $500 million, perhaps $1 billion after milspecking, expensive compared to military planes, cheaper than major naval combatants.
This is no small ship. If the propellant is liquid hydrogen the tanks have a volume of about 7000 cubic meters, equivalent to a 7000 ton submarine. The payload section is about two thirds the mass of the ISS and of roughly comparable size, though the hab is probably spun giving the prolonged missions.
Armament is necessarily modest. The 75 tons of additional payload allowance probably must include a ferry craft for the espatiers and an escort gunship or two, plus their service pod, leaving perhaps 15-20 tons each for kinetics and a laser installation. The laser might be good for 20 megawatts beam power, with plug power from the 200 megawatt drive engine.
This ship is no laser star, but the laser is respectable. Assuming a modest 5 meter main mirror and a near IR wavelength of 1000 nanometers, at a range of 1000 km it can burn through Super Nano Carbon Stuff at rather more than 1 centimeter of per second. Its armament is also rather 'balanced.' My model shows that this laser can just defeat a wave of about 1000 target seekers, each with a mass of 20 kg, closing at 10 km/s—thus a total mass of 20 tons, comparable to its kinetics payload allowance.
Deploying troops, or personnel in general, is impressively expensive: About three fourths of the payload and cost of a billion dollar ship goes to support and equip a crew of 25, with perhaps a dozen espatiers. For comparison the USS Makin Island (LHD-8) displaces 41,000 tons full load, carries a crew of 1200 plus 1700 Marines, and costs about $1.8. So by my model it costs about as much to deploy one espatier as 80 marines.
And this ship is about the minimum patrol package, so standing interplanetary patrol is a costly and somewhat granular business, something not everyone can afford.
TONY: I was maybe a little bit hasty earlier in saying that patrolling was of no value. It does have the value of giving you immediate reaction capability in a crisis. And in an environment where transit times are weeks or months, that can be important. IOW, while there may well be no physical horizon to patrol beyond, there is a time horizon.
However…a patrol vessel for that purpose could not be a relatively fragile assemblage of modules and cargo. This ship is going to have to fight it out with whoever else has a patrol vessel on-station — as well as any local forces that might exist — then dominate the local space until reinforcements arrive. So it's either got to be analogous to a pre-WWI overseas station cruiser, or the operator has to accept abandoning the hab and interplanetary drive (perhaps permanently) in order for the rest to be able to fire and maneuver effectively.
FERRELL: I don't think that "space patrols" would be like navy, or even air force patrols. It would be more like a giant figure-8 in the sky. Only with weapons and spy-gear...I do think that the 'patrol ship' would have extensive spin-hab and payload sections, but I think that the weapons mounted on the ship would be mostly point-defence, while the ship would also carry drones that mount the offensive weapopns (missiles and/or lasers)and be controlled from the ship. I also think that 'partols' would be more like convoy escorts (or raiders), 'show-the-flag' type, area security (like orbit), but I don't think you're going to send a billion dollar spacecraft from orbit 'A' to orbit 'B' and back again, just on the off chance that they would run into an enemy 'craft. It would be more like the bomber-interceptor type of combat. Deverting a 'show-the-flag' patrol to a hot-spot would be the exception rather than the norm. The only reasons I can see that you'd have these ships on a 'patrol' like Rick has discribed, is to keep close to convoys, unfriendly folk, or as mobile intelligence-gathering platforms. The customs/law-enforcement/anti-piracy/counter-terrorisim mission for your espatiers would be secondary. I further think that 'patrol ships' could be more like a mobile space station that are sent to orbit a planet or moon for short amount of time, and then off to the next target.
So...'space patrols' aren't going to be like 18th century sailing navy patrols, or even modern-day SSBN patrols. If you could send railroads on combat patrols, 'space patrols' would be like that...
ELUKKA: Shameless plug: I happened to design a paramilitary patrol/interceptor ship recently. Well, not really a coincidence as it was inspired by a previous discussion here. It'll manage an interplanetary flight but I imagine it's made more for smaller operational areas, say a gas giant's moon system.
Open-cycle gas core NTR engines, thrust around 1 g (or nearly 3 with LOX injection at the cost of some isp), delta-v 30 km/s. Propellant is methane. There's a secondary chemical engine for operation near other craft as the main engines do have radioactive exhaust.
It has a fairly big 140 tonne hab module and a turreted laser. Total mass is about 2,200 tonnes. Besides going with a high-thrust engine, I find it surprisingly similar to the craft Rick described!
The hab's got a wraparound radiator and the engines get rid of the brunt of their waste heat by the way they work (open-cycle cooling) but… no, they're probably still not enough. I did a terrible thing and sorta threw on radiators that I thought looked good instead of running the numbers. :P
(I did mathify the rest of the design though)
click for larger image
click for larger image
ELUKKA PATROL SHIP Engine Open-cycle GCNR Docking Engine Chemical
Propellant methane ΔV (High-Gear) 30,000 m/s Wet Thrust (High-Gear) 1g ΔV (High-Gear) 30,000 m/s Wet Thrust (Low-Gear) 6g ΔV (Low-Gear) ? m/s Habitat Module 140,000 kg Weapons x2 laser turret Wet Mass 2,200,000 kg
FERRELL: Elukka:, your ship is great! As an interceptor or convoy escort, it looks like a good compromise between cost and mission demands. I could see it being used very handlly as a customs inforcer or as an asteroid deflector, as well as other missions. As a secondary armed spacecraft, this is what I imagined a "real" space fighter would be like. Your ship would be perfect for an independent colony or minor power.
We already have space patrols, and we call them spy-sats.
I just don't see this scenario. The cost, the mass, the vulnerability of a single mirror as our primary means of offense and defense.
So your laser can burn 1000 incoming big projectiles? Big deal. This has always struck me as the major flaw in single laser configurations—the assumption that the enemy won't just buckshot you to death.
Imagine this patrol ship up against robot ships using auto-canon to blast out clouds of shrapnel heading your way from beyond your laser's range and riding into your projected path of travel.
Sure, they miss a lot, but they have hundreds of thousands of projectiles zipping towards you too. How do you track a cloud? How do you blast it? Can you paint that much space with your laser before overheating? (the answer is that is debatable, the classic Purple/Green debate)
All it takes is for the shrapnel to rip apart your mirror, or radiators, or sensors, or whatever.
And then boom...
Here comes the slow nuke to turn your patrol ship into a flash of light that no longer exists.
More realistic are lots of robot patrols—cheap and expendable. They swarm. They spy. They report. And eventually they fail and self-destruct. No muss. No fuss.
Plus they're cheap and easy. NASA could build these today if it wanted.
Sorry. I just don't see this scenario as very plausible.
Hey—I just had a weird idea for these drone ships.
Do you think it would be possible to design them to cannibalize themselves for ammunition?
In other words, they'd lock onto a target, fire their basic store of ammunition, and if the target wasn't destroyed, the drones would be built in such a way that they could begin consuming their parts for ammo until the drone was nothing but the basic power unit, firing computer, attitude determination and control system (ADCS), and the rail gun.
Everything else. The shell. Primary thrusters. Etc… Fired down range. I wonder how much you could scavenge if you had no intention of bringing it home again. (This is done in the simulation game High Frontier, except more so. The ships have Santa Claus machines that can canabalize unused equipment and manufacture needed equipment)
(Somebody suggested to Clay that patrol ships would be for inspection, not main-line combat work. Therefore it wouldn't matter that patrol ships were vulnerable to a sky full of buckshot)
Well, these patrol ships are obviously meant for combat to some extent if we are arming them. My argument is that arming them, and indeed sending them, is pointless.
Patrol ships can't outfight the drones cost effectively, nor can they out-patrol the drones either from a cost-effective standpoint.
And I've read the arguments regarding space battle here and elsewhere, but I think they bear repeating in this context.
There just isn't a scenario where dispatching isolated patrol ships with limited weaponry for long-range reconnaissance makes any sense unless you are actively trying to get attacked in order to justify going to war (a la American PT boats harassing Japanese warships pre Pearl Harbor)
My overall view on this is that any sort of presence patrol will be in the form of a station, not individual ships. It's far cheaper in remass, and you get more ship for your money, as you don't need deep-space endurance. There might be a few ships for flag-showing patrols, but those would be very rare.
Tony, Yes, but there are two major problems with that. First, the fact that you spend as much time coming back as you did going out. Second, the fact that you are only "on station" for 1% of the time. Yes, you can stop at the target, but the mass penalties for that sort of thing are rather severe.
Elukka: The ship looks impressive. Do you have any more numbers?
Clay, a single big laser will tend to be more powerful than several small ones. It has a longer effective range, and thus starts burning things sooner. I do agree that a few defense lasers would be helpful, but the main offensive laser will likely be a single unit.
As for attacking lasers, I'm in favor of sand clouds.
The point of armament is to provide the ship with some sort of chance against an enemy. If they can't outfight drones (which I won't take as a given) they still will do better with guns than without guns.
If anyone's interested in ship design, I've recently made a spreadsheet that automates a lot of it. It was originally for Rocketverse but it's pretty adaptable. If you want a copy, I'll find a way to get it to you. I also have a Newtonian space battle tracker that works with it.
I think patrolling in space is a waste of time. You're wasting energy and reaction mass putting your ship in one particular orbit — thereby pretty much guaranteeing no enemy will be encountered in that orbit.
The life-support cost is tremendous — not just in launched mass but also radiation exposure and the "opportunity cost" of having those crewmen on a trajectory to point A rather than any other point. Given the capabilities of modern drones I can't imagine any spacefaring power which would send out humans to snoop around potential threats.
Instead of a patrol ship, I'd envision something like a frontier fort — a base from which missions can be launched, with telescopes to monitor that whole part of the Solar System, hardened defenses, long-term self-sufficiency, etc.
One can imagine "forts" like that in key locations around the system — Saturn orbit, possibly the Jovian trojans, etc.
The only reason to send manned ships is for "courtesy visits" and that's a pretty flimsy excuse. If your intel people are reasonably competent, they'll have agents aboard cargo ships going there. I somewhat agree with the "fort" theory, but I'd go farther and make it a full base, with facilities for crew and family, moderate repairs, etc.
Patrolling will reduce the time horizon for the force which engages in it, which is really the point, I think.
Arguments that the patrol vessel is vulnerable are somewhat moot, since if the vessel is attacked, then it is an unambiguous signal that hostilities have commenced (unless the owning Power is willing to tolerate the loss for political or military reasons of their own).
I would argue that a patrol vessel on the lines Rick has described would be a two part vessel. The Hab would be an independent space vehicle in its own right, while the major portion of the ship (keel, engines, radiator main assembly, Liniac and mirror) are also an independent vessel. Once the decision is made to land a shore party (or liberty party for that matter), the hab undocks and trundles off while the weapons platform remains in the High Guard position (Overwatch position higher in the gravity well).
For Elukka, who seems to have a flare for this sort of thing, the main platform would look somewhat like a paper airplane, with large triangular radiators along the truss. The engine is at the wide end (radiators corresponding to where most of the heat generation is) (engine might be at the pointy end if it emits radiation) and the mirror is in the nose, perhaps in a "thimble" turret at this scale. Tankage, KKV's etc. are in the spaces between the "wings", and the hab is hanging off one of the hard points. Depending on the scale (and given the description), the hab might resemble a pair of spare tires hanging from a medium length girder bridge (counter rotating so they do not impart momentum to the carrier vessel). If you really want to take the "paper airplane" analogy seriously, then there are three fins and most of the other hardware is attached to the truss on the "top" of the paper airplane.
The big advantage of this design is the carrier need not go with a manned hab, and indeed the hab could be the control station for a constellation of these vehicles, making it adaptable for everything from patrolling to being the nucleus of a constellation or task force.
It wouldn't reduce the time horizon by enough to matter in most cases. Not if the opponent was smart. If you're basically going there, swinging through the system, and leaving, the time in the system is going to be minimal compared to transit time. It's like sending "patrols" to, say, Deigo Garcia from the US by steaming a ship all the way around the world, and not stopping there, just sailing close by once, and leaving. Oh, and the ship can't turn around once it's past. Response time might be less if you have two, but no matter what, they'll wait until you've passed to make trouble.
If you choose to stop in orbit, that's slightly different, but unless you only want occasional visits, it makes a lot more sense to build a permanent base. You only have to ship supplies, and your crews will be a lot happier. Plus, the ships you have won't have to carry stuff like spin habs, as the missions aren't that long.
I think some people are not understanding what a patrol is in the context of near and medium term interplanetary spaceflight. The bojective will not be to go there and come back, or go to several places and pass through each without stopping. The objective will be to go and stay for the suration of the mission (months or years), so that if anything happens somebody will be on-hand to handle it. The patrol area is not a large volume of space. It's the tactically relevant volume of space around a point of interest, like a planet or an asteroid. So yes, there are some affinities with the fortress analogy and the spy sat analogy, but only some.
The patrol ship needs to do three things:
- Go to the patrol area
- Remain on station
- Fight if and when the time comes to fight
Notice that these three requirements would best be met by three different spacecraft. But since we don't have three different spacecraft, we'll make do with three different modules:
The interplanetary module takes the hab and the combat modules to the patrol area. The hab is lived in and the combat module manned while on patrol station. If shooting starts, the combat module detaches from the hab and goes to work.
- Interplanetary propulsion
Note that the combat module need not be monolithic. It could be augemtned by orbital or even self propelled sensor and weapon platforms. The reason for its existence — and the existence of the whole patrol ship complex — is to place humans in the loop in tactical time. It doesn't exist to be a tripwire, or to be here one day but gone the next. It exists to be available to fight and to actually fight when called on to do so.
I'll note that I am only against deep space patrols. Ships in orbit around an enemy planet (or a partially enemy planet, such as a multi-faction world or a friendly world that's under invasion, or a potentially enemy planet, that you suspect but aren't sure is planning something nefarious) can reasonably make use of some patrol tropes, although it's not quite the same.
One issue with "patrolling" this close to an enemy planet, without access to stealth, is that the enemy is unlikely to let you unless you show up in enough force to strongarm their defenses. If relations are merely strained rather than actively hostile, though, then a show-the-flag mission is viable.
Tony: "I was maybe a little bit hasty earlier in saying that patrolling was of no value. It does have the value of giving you immediate reaction capability in a crisis."
Only if you know in advance where the crisis is going to turn up.
The extreme difficulty of changing course in space means that you cannot hang around in a trouble spot and be ready to give chase if something comes up. The mere size of space means that there isn't going to be any narrow region of space you can keep an eye on to keep most trouble under wraps, unless that region is in orbit around a planet.
Clay: "This has always struck me as the major flaw in single laser configurations—the assumption that the enemy won't just buckshot you to death."
I think there is practically no point defense that can help against buckshot. Even a small amount of armor, however, can.
Byron: "My overall view on this is that any sort of presence patrol will be in the form of a station, not individual ships."
A fleet of ships can be in several places at once, which is useful when you're trying to keep an eye on an entire planet. I don't think a patrol craft benefits that much from being large, except in as far as that it gives you more room for crew amenities to endure the long boredom.
Milo, you misunderstand what I meant. I was trying to say that a long-term patrol won't be carried out by ships on rotation from a home base at a different planet. Instead, a base will be constructed in the system, and ships will be more-or-less permanently assigned there while the crews rotate.
The problem is that to be capable of carrying a crew on an interplanetary voyage, a patrol craft will have to be large. My stations solve that, as they only have to deal with the normal crew under peacetime conditions for a month or two at most. If you need to move it back home for a refit or something send a skeleton crew.
Milo, the whole point of patroling is that you don't know when or where the crisis is going to be, so you maintain a presence where you have an interest, ready to react when one does.
Also, the size of space and the difficulty in changing direction dictates precisely that you can only focus on well-defined regions of interest. The only such well-defined regions are those within tactically relevant distance of a point of interest, like a planet or an asteroid. Anyplace else has little if any strategic value and just ain't worth fighting over -- not that anybody would go there in the first place.
About the only situation in which you might get combat away from natural bodies is if two powers launch comparable warships through the same window at the same destination, and either one or both ofthem had enough spare delta-v to maneuver into combat, fight it out, and still make any necessary orbital correctios and orbital insertions at the destination.
Milo, Ahhh, but that small amount of armor isn't so small given mass constraints. Even a little—and we don't know ahead of time how "little" it gets to be because we don't know what the scenario will be—can radically reduce the overall amount of Delta-v available, or else run up the price tag.
And there's a Catch-22 with up-armoring your ship. Once you do a little, and the price goes up, then you feel the need to protect it even more since now that ship represents a bigger investment. And so on and so forth.
And yes, I know a big laser is theoretically better than several small ones, but it also puts all your eggs in one basket. Again, you don't need to destroy big-gun patrol ships with buckshot, you just need to screw up their mirror or mess up their radiators, etc…
That's the problem with space warships. They're like flying aircraft carriers in modern war. Theoretically useful, but too vulnerable to justify the expense.
In this case, we either have real warships or automated spysats. Why build a ship that isn't powerful enough to really fight, only to take a look at stuff that can be observed at far less cost by automated spysats.
Even if there is trouble, the patrol vessel isn't really a warship. It will quickly get overwhelmed, and it won't take much to do it.
MR. BLUE: Don't forget one very important role for Patrol Ships: Deep Space Search and Rescue. Think of it as an analog to today's Coast Guard cutters.
So, the espatiers would be have a good levening of Pararescue types to effect rescues inside damaged ships. Add a pretty good trama center onboard ship.
The ship would need to be armed, but it would not really be used for classic warship to warship combat. You would mostly use the laser to vaporize or move any potentially hazardous debris. That laser would also come in handy if you needed to slag a fleeing smuggler or rogue missle.
I will split my responses to points into mainly technical and mainly strategic.
I've come to be doubtful that armor is worth the mass penalty. Any kinetic strike that saturates a decent laser defense will probably overkill the target, while a laser will zero in on vulnerable points rather than just zap away at armor.
For the same reason, military craft might not look much different overall from civil ships, apart from the actual weapon mounts.
The advantage of range (and more zapping intensity at any given range) justifies a single main mirror, I think. Tanks have one main gun, and they are much more subject to being engaged from an unexpected bearing.
I like the idea of being able to detach sections. There are some mass penalties, but mostly pretty minor ones. One constraint, in my presumed tech, is that the laser draws electric power from the main drive, so is necessarily connected to it.
For interplanetary missions the distinction between 'ship' and 'station' is quite blurred. Attach a drive bus to a station and it becomes a ship; remove the drive bus from a ship and its hab becomes a station.
The ship I outlined is not intended for 'combat patrols.' In an all-out shooting war the patrol ships may as well be mothballed for the most part.
They are intended for missions more comparable to those of coast guard cutters, Victorian gunboats, and Teddy Roosevelt era 'peace cruisers.' Basically wherever a polite request and a 20 MW laser will get more compliance than the polite request by itself would.
So the armament is not primarily to engage peers but to provide a clear dominance over jury-rigged or other light armament.
Whether there is a valid mission for these ships is a valid question. To be strictly realistic, there probably won't be anything beyond Earth orbital space but research stations, and an extremely minimal military/police presence comparable to Antarctica today.
But if you are going to assume a future Solar System filled with all sorts of activities, power players are going to want intermediate coercive options between sternly worded protests and interplanetary kinetic/nuclear strikes.
Rocketpunk Patrol Ship
Dry Mass 76.2 metric tons Wet Mass 384.6 metric tons Mass Ratio 5 Length Z 73 meters Length Y 20.1 meters Length X 15.2 meters Engine x2 F-26-A LH/LOX Thrust 7.7×106 N Acceleration 0.5 g ΔV 8,200 m/s
This is the same one from the other day, only dressed up with a nice logo and some stats. These are realistic capabilities made courtesy of the charts and other information available from Atomic Rocket and inspiration from Rick Robinson's Rocketpunk Manifesto.
My PL differs from the one in Rick Robinson's article in a few key areas. The main difference is that it is not made for long hauls. It only has a delta v of about 8200 m/s. This will not get one far in the solar system but it allows a forward deployed Patrol Craft a sufficient "range" to perform many of the missions we discussed in the last post on Building a Space Navy. Our little A-Class has enough Delta V to shape a light-second orbit around a convoy in deep space, conduct SAR missions anywhere in cis-lunar space, or to reach any moon of Saturn from any other moon. Obviously, this rocket is mostly propellant (mass ratio 5). If you drew lines through the side view of the rocket that bracket the docking rings, you would encompass the entire pressurized volume. I've got to say, it's nice to work on a warship for a change — I don't have to make it economical to run!
One of the interesting things about this design is actually the freedom the little carried craft gives me. It was a throw-away touch, originally — a design borrowed from another project. But as I got to looking at the little thing, I realized that it's about the size of the Saturn V stage/Apollo/LM stack. That means it should be able to go from Earth Departure to Lunar orbit. That means that it has the Delta V to ferry crew to and from a Patrol Craft on station away from the convoy. That means, like submarines, our Patrol Craft can have two crews and stay out for a lot longer than otherwise. This is one of those realistic touches that I hope add to the charm of the rocket's design.
ed note: a 1500 nanometer near infrared laser with a 10 meter fixed mirror can have a 4 centimeter spot size out to 220 kilometers or so. A 4 meter mirror can have a 4 centimeter spot size out to 87 kilometers or so.
If you have an atomic-rocket future you will need atomic rocket fuel. This means atomic fuel plants to turn raw uranium ore into refined fission fuel reactor elements (or whatever), and fuel reprocessing facilities to reprocess spent fuel rods into fresh ones.
Unavoidably this will produce sizable amounts of weapons-grade fissionables, just the thing for making your very own nuclear weapons.
The Nuke Guard is the military security force charged with preventing any of this stuff from being stolen. Because the last thing you want is a load of Plutonium-239 going walkies out the door and into the hands of terrorists or revolutionaries. Nuclear Security in other words.
Much like the Spaceguard this might have to be a mult-national force. So they can keep each other honest. This also might have to be a full military service instead of a civilian one. Let's face it, security guards at a plant are seldom equipped to fend of a full military raid by a hostile foreign power trying to capture stocks of weapons-grade plutonium.
And if you think the Nuke Guard is hard-core with absolutely no sense of humor, obviously you have not yet met the Antimatter Guard.
Mass drivers and other rockets can be used to alter the orbits of asteroids (and mass drivers can use rocks from the asteroid itself as a built-in source of propellant). Popular with asteroid miners who want to nudge their claims into different orbits. Unpopular with the astromilitary of all nations, who think that civilization-destroying asteroid bombardment is not a power one wants to give to rock-rats.
The "Dinosaur-killer" asteroid was probably about 10 kilometers in diameter, and it caused a freaking mass extinction of three-quarters of plant and animal species on Terra. There are approximately ten thousand asteroids in the belt of size 10 km or larger. And of course there are much more than ten thousand "fun-sized" asteroids, not large enough to wipe out civilization on Terra, but big enough to obliterate a nation that you dislike. Space faring nations with asteroid moving technology will look at the list of small asteroids, look at the list of nations hostile to them, and start to get ideas.
If asteroid moving technology is cheap enough it won't be a game just for nations, you might find mere corporations and James Bond villains getting into the act.
Once asteroid-moving technology is available, one can foresee a branch of "spaceguards" in each astromilitary, patrolling the solar system to prevent unauthorized changes in asteroid orbits. Any rock-rat, corporation, or nation that wishes to move an asteroid will have to file a proposed trajectory and request a permit from the Spaceguard.
(ed note: Originally I called this branch the "Orbit Guard." I have gone to the trouble to change the name for two reasons:
 The term Spaceguard is already being used for this function.
 The term "orbit guard" is a much better fit for the space-going version of the Coast Guard.
I regret any inconvenience this has caused.)
The Guard would keep a close watch on all asteroids. If one starts to move without a permit, or if one with a permit strays off the filed flight plan, military spacecraft of the various space faring nations will pounce and blow the snot out of it. Spaceguard ships will be armed, since the evil asteroid movers will probably shoot back. Of course prior to that the evil asteroid movers will have all their crew and equipment scrubbed of anything identifying the nation behind this heinous act, since it easily fits into the category "act of war", or even "genocide."
Probably there will be a branch of spaceguards in all of the space faring nations. They will not just watch asteroids, they will also keep a close eye on the spaceguards belonging to other nations, just to keep them honest. If nation X has a spaceguard, enemy nation Y will want their own spaceguard as well. Otherwise nation X might be tempted to turn a blind eye to somebody targeting nation Y's capital city with an errant asteroid.
Requests for asteroid moving permits will have to be filed with the Spaceguards of all nations. Things might get a bit political here, since giving all the Spaceguards veto power can be abused. Say, if nation X was currently angry with nation Y, nation X might pressure their Spaceguard to automatically veto any asteroid moving requests from nation Y using specious reasons. Some kind of appeals process will have to be available.
And who knows? Spaceguard might actually find an errant asteroid that just happened to be naturally on collision course with Terra, instead of uncovering a Sinister Plot by Dr. Evil. It will be real nice to have the spaceguards there to bump it off course. Just ask the dinosaurs. Oh, that's right, you can't because an asteroid made them all go extinct.
Arthur C. Clarke invented an asteroid early warning system called "Project Spaceguard" for his novel Rendezvous with Rama in 1972. Clarke was most gratified when a real live Spaceguard was created in 1992 (duely giving Clarke credit for the name). David Levy stated in an interview "The giggle factor disappeared after Shoemaker-Levy 9." After the impact of Comet Shoemaker-Levy 9, asteroid detection programs all over the world abruptly received greater funding.
The main point is it is quite easy to nudge an asteroid off collision course if you have a few decades of lead time. If you only have a few days notice you are going to have to use nukes. So start discovering and surveying all those Near-Earth objects right now.
A separate but closely related duty performed by the Spaceguard is that of range safety officer. If civilian ships can be used as weapons of mass destruction, in an emergency the Spaceguard can remotely trigger the civy ship's self destruct device. Spaceguard shares this responsibility with the Launch Guard. Generally the Launch Guard's range safety keep watch around spaceport launch sites while Spaceguard's range safety officers keeps watch everywhere else. As far as Spaceguard is concerned, a civilian spacecraft on collision course with a colony is the functional equivalent of a rogue asteroid. Only of artificial origin and hopefully already equipped with a handy self destruct.
Spaceguard will also blow up any civilian-owned torchship which starts to aim its lethal exhaust at something vulnerable. Again, regardless of whether it was deliberate or unintentional. The ship might be given a radio warning first, but they have not complied within the specified time limit, it is kaboom time. Spaceguard does not know or care if it is due to a drunk pilot or terrorist activity: civilians are forbidden from giving impromptu demonstrations of the Kzinti lesson.
Spaceguard is a nice concept for SF authors, since it gives a plausible reason for the very existence of astromilitary. And of course civilian boom-towns and settlements will spring up around any military bases. There is money to be made supplying all those enlisted people with gambling, whiskey, and prostitutes. Especially if the base is orbiting Saturn or somewhere equally remote. This gives SF authors an economic reason for an extensive manned presence in space.
Getting a Spaceguard system set up is going to be tricky. Quis custodiet ipsos custodes? and all that.
Before spaceguards with space ships are established as a branch of the military, any civilian attempts at asteroid re-direction will have to be accompanied by a division of army solders. From several nations. Every propulsion event will have to have the math checked by military astrogators. Of each nation. And the execution of the propulsion events will be closely monitored. At gun point. Of each nation.
Don't forget the army fire-teams tasked with aiming their weapons at each of the foreign army divisions, just in case they try pulling a fast one. Don't drop an incandescent light-bulb or otherwise make a noise sounding like a rife-shot. Otherwise when the firing stops everybody will be dead and the room will look like a colander.
It is probably a requirement to have several nations establish spaceguards with space ships, since a single nation with a monopoly on orbit guards is dangerous. Not just that the owning nation might issue covert orders to "accidentally" drop an asteroid on hostile nation Y. There is also the danger that a spaceguard ship might revolt, be infiltrated by terrorists, be composed of enemy sleeper agents, snap under the pressure and go insane, be part of a military coup conspiracy, or otherwise turn rogue and drop an unauthorized rock on some nation. Including the owning nation.
If there are spaceguard ships from other nations constantly watching your spaceguard suspiciously, it becomes much more difficult for a ship to go rogue. It is much safer to have several nations with spaceguards.
Perhaps it would make sense to have something like the Two-Man Rule used in nuclear launch protocol. Spaceguard ships of a given nation would go in pairs, watching each other. Or in triples, in case one ship becomes disabled. You see how the complexity quickly snowballs.
However the Two-Man Rule was designed to prevent something from happening, not to ensure something happens. If Spaceguard ships Alfa and Bravo are near an asteroid, and Bravo turns rogue and tries to push the asteroid so it obliterates Terra, then according to the safeguard of the Two-Man Rule ship Alfa will shoot the ever-living snot out of ship Bravo. Everything is fine.
What is not so fine is if ships Alfa and Bravo are trying to save Terra by redirecting an asteroid aimed by Dr. Evil. Ship Alfa can start the redirection process, only to get the ever-living snot shot out of it by the subverted Ship Bravo. In this case the Two-Man Rule fails to ensure the desired result happens.
The spaceguard ships also might contain self-destruct devices, controlled by the owning government. Though you'd better be darn sure the enemy doesn't get its hands on the destruct codes. Or you will be really angry when your entire spaceguard fleet goes poof!
However, a spaceguard can still be used for nefarious purposes, such as making an excuse to annex the Asteroid miners.
The Spaceguard spacecraft will carry their own high thrust equipment in order to re-direct errant asteroids. A nasty government might aim a large rock at an enemy nation then destroy the mass driver they used. The Spaceguard cannot count on the equipment being available to redirect the asteroid. The equipment might also become damaged in the battle to clear the asteroid of hostiles, especially if the bad guys use the mass driver as an impromptu kinetic energy weapon. The Spaceguard will be forced to neutralize the mass driver, which is never good for its warranty.
Scott Lowther figures that Orion drive style nuclear pulse units would be perfect tools for a spaceguard to redirect asteroids. Remember, they are not nuclear weapons that radiate their blast isotropically. They are nuclear shaped charges radiating about 85% of the explosive energy into a 22.5° cone.
Orion nuclear pulse units are more or less designed for the task (spacecraft pusher plate, asteroid, what's the difference?), they are powerful, small enough that any sized spaceguard ship can carry a large number of them (about 0.6 meters tall by 0.36 meters in diameter, mass 79 kg), and are certainly far more portable than lugging a full sized mass driver. If you position the charges far enough, the tungsten propellant will spread its impact evenly over the asteroid's entire hemisphere. This helps ensure that the asteroid is just nudged off course, not shattered into a deadly charge of cosmic buckshot still aimed at Terra.
The standard nuclear charge used in the USAF Orion report had a yield of one kiloton and would hit the asteroid with about 2.01 megaNewton-seconds of impulse. The Chelyabinsk meteor had a mass of about 10,000 metric tons. One USAF pulse unit would change its velocity by 0.2 meters per seconds. Doesn't sound like much but in the real world it's pretty good. So a single USAF charge could have made the Chelyabinsk meteor miss Terra by 100 kilometers if it was placed to detonate about six days before the meteor was scheduled to strike Terra. Or ten charges could make it miss by 100 kilometers if there was only 14 hours lead time prior to Terra impact.
If Spaceguard ships carrying Orion nuclear pulse units does not appeal to you, then perhaps the Spaceguard ships will have mass drivers as propulsion. And a large thrust bracing on the nose. After the resistance has been neutralized (i.e., all the evil asteroid movers have been blasted or are in custody) the Spaceguard ships will land on the asteroid, ship noses pressed into the aseroid's surface and the ship tails pointed skyward, deploy scoop conveyor belts to grab reaction mass, and start running their mass drivers at full bore.
Legitimate and illegitimate asteroid movers will probably have to make do with mass drivers instead of Orion pulse units. Most military forces are quite unreasonable about allowing nuclear devices into civilian hands. Evil asteroid movers might illegally use Orion units, but they will have to work quick. Multiple nuclear detonations will be visible all over the solar system and will quickly draw unwanted attention.
SpaceWorks Engineering did a study for NASA about deflecting killer asteroids on collision course with Terra. The concept they came up with is Modular Asteroid Deflection Mission Ejector Node (MADMEN) robots. They are unmanned, independently controlled, nuclear powered, and equipped with a powerful mass driver. The idea is to make a solution that is "scaleable". If the asteroid is larger, then send more MADMEN modules. Plus a few extras in case some of them suffer malfunctions.
A transfer vehicle delivers a MADMEN to the impactor asteroid. The MADMEN lands at the correct spot, the landing gear digs in to anchor the MADMEN, the heat radiator and mass driver unfurls, the reactor powers up, a drill head extend into the body of the asteroid to gobble rocks for mass driverpropellant, and the mass driver proceeds to lob the rocks at a rate of one per minute. If the asteroid is rapidly rotating, the MADMEN is intelligent enough to only fire a rock when the rotation brings the mass driver to point in the desired direction. The thrust of the mass drivers gradually alters the trajectory of the asteroid into a safe direction.
These would be useful to both Spaceguard and to evil asteroid movers. Spaceguard can station caches of MADMEN in strategic locations, without having to worry about life support for Guard crews (MADMEN are unmanned, remember?). Evil movers will not have to worry about Spaceguard capturing evil crews, who might be coerced into revealing which evil nation is responsible for the evil plot. MADMEN may also be easier for evil asteroid movers to secretly emplace on a lonely asteroid, but the onboard reactor and heat radiators will rapidly give away their positions once powered up.
|Baseline MADMEN lander parameters|
|Ejection Velocity||187 m/s|
|Ejecta mass per shot||2 kg|
|Mass driver length||10 m|
|Shot frequency||1 per minute|
|Total surface time of proces||60 days|
|Total power required||42.2 kW|
|Dry Mass||1,503 kg|
|Gross Mass||1,621 kg|
|Baseline mission parameters|
|Delta-V imparted to Killer Asteroid||0.2 m/s|
|Killer Asteroid Mass||2.7 × 109 kg|
|Killer Asteroid Diameter||130 m|
|Delta-V to get to Killer Asteroid||5,423 m/s|
|Dry Mass (with MADMEN payload)||2,207 kg|
|Gross Mass (with MADMEN payload)||8,816 kg|
An earth protection system against asteroids and meteorites in colliding orbit is proposed. The system consists of detection and deorbiting systems. The analyses are given for the resolution of microwave optics, the detectability of radar, the orbital plan of intercepting operation, and the antimatter mass required for total or partially blasting the asteroid. Antimatter of 1 kg is required for deorbiting asteroid of 200 m in diameter. An experimental simulation of antimatter cooling and storage is planned. The facility under construction is introduced.
The space activities of mankind have been supported by
1) curiosity in sense to find new laws of universe and in exploration to find new world.
and will be so in future. Another motivation of space activities especially in future is
2) desire to preserve the human race, i.e. instructive move for survival.
The second motivation may take the form of Solar Power Satellite (SPS) and human resource exploitation, i.e. helium 3. These are counter action against the energy crisis coming in future. The energy crisis is related to the expansion of human activities. On the other hand, there is another type of crisis, the natural disaster caused by asteroid collision with the earth.
Asteroids approaching to the earth have so high relative velocities about 30 km/s that the kinetic energy is extremely large even if it is much smaller than the earth. Asteroids collision with the earth result in not only the craters formation and tidal waves but also the earth environment modification. The Hiroshima atomic bomb has an energy of 1015 J, which corresponds to the estimated kinetic energy of a meteorite, 10 m in diameter and 5 in specific gravity. Celestial body in 10 m class crashes on the earth once every several hundreds years. It is reported that a collision with a meteorite in the Cretaceous period changed the climate and exterminated the dinosaur in the mass. The collision correspond3 to 5 billion Hiroshima bombs. The asteroid collision equivalent to the dinosaur extinction happens once per 100 million years.
Asteroids very frequently near-miss the earth as shown in Fig.1. Figure 1 is not a complete list since the asteroids in Fig.1 were accidentally observed by voluntary observers. The 1989 FC passing by the earth on March 22 in 1989, had several times as large kinetic energy as the asteroid which formed the Arizona's famous 1.2km meteor crater.
Antimatter annihilation propulsion for interstellar and deep space missions has been recently studied because of high energy density of antimatter-matter reactions. Most of the studies emphasize the mission analyses and the conceptual designs of antimatter engines. On the other hand, we have been studying the storage of the antimatter and considering the application of the earth protection system against asteroid collisions.
The asteroids uf 10-100 m size, which had impinged in the ocean and caused global weather impact, may not be recorded in the history books.
The earth protection system presented here not only actively detects the celestial bodies approaching to the earth but also modifies their orbit. The objectives of this paper are:
1) to estimate distance to detect asteroids from the earth and remaining time before collision,
2) to estimate requirements for radar system characteristics using Very Long Base Line Interfercmetry (VLBI),
3) to estimate the amount of antihydrogen for the orbital modification of meteorites,
4) to examine antimatter storage,
5) to design the antimatter factory and base.
REMAINING TIME BEFORE ENCOUNTER
In order to make the analysis simple, three dimensional effects such as the inclination of the asteroid orbit are ignored. Meteorites are either comets or minor planets. Based on orbital data of comets, the eccentricities are found around 0.8 and the distance of perihelion ranges from 0.13 to 0.98 a.u..
Figure 2 shows the relation between the remaining time and the distance. The asteroid is assumed to move frem the aphelion toward the orbit of the earth in the calculation. While the orbital radius distributes from 2 to 3 a.u. in the case of meteorites which are categorized as minor planets. It is concluded from these results that the distance to have to detect the asteroid is 1 a.u. and the remaining time before encounter is from 2 to 3 months.
RADAR SYSTEM BY VLBI
The radar system is required to detect and track an object approaching to the earth as soon as possible. Suppose the asteroid of 100 m in diameter is detected at 1 a.u. distance from the earth. A great number of celestial bodies are observed by the photographic method with large telescopes. Asteroids approaching to the earth are discovered and tracked by the radar. The precision for the tracking radar requires 0.1 nrad in angular resolution. Such a resolution can be achieved by VLBI in radio astronomy such as VSOP (VLBI Space Observatory Program) in Institute of Space and Astronautical Science (ISAS). For the purpose of determination of transmission power of microwave, wave length, diameter of antennas and baseline distance, it is assumed:
1: Antenna for microwave transmission are the same size as receptive one.
2: Receptive sensitivity is 10-20W.
3: Microwave is scattered at the asteroid's surface uniformly and isotropically.
4: Reflectivity of asteroids is 0.1.
The first assumption is made only for convenience. The second precision corresponds to an observation of a radio galaxy with 1 mJy (1Jy=10-26Wm-2Hz-1) by a radio telescope which is 100 m in diameter and 100 kHz in band width. The third assumption is very natural since the surface unevenness is larger than the wave length. The reflectivity of Apollo objects is assumed to be 0.1.
Now we derive the relation between the transmitted and the received power. Microwave beam diverges with transmitting distance. The theoretical minimum for beam collimation is given byA: cross sectional area of microwave beam
L: distance between asteroid and the earth
d: diameter of transmit and receptive antenna
λ: wavelength of microwave.
The power received by the receptive antenna is given by the equationPa : received microwave powerThe angular resolution of VLBI can be estimated to be the order of λ/L. The power required for each satellite is about 10 kW if the millimeter wave is transmitted at 10 Hz repetition with the pulse width of 10 μs. The required characteristics of the radar system are summarized in Table 1.
Pt : transmitted microwave power
δΩ : solid angle of receptive antenna measured from asteroid
D : asteroid diameter
Table 1: Specifications of the Radar System diameter of asteroid 100 m diameter of antennas 25 m received power 10-20W wave length 0.1 mm peak power of microwave 100 MW number of transmission satellites 10 baseline distance 1000 km
As exhibited in Table 1, these satellites are only 2.5 times larger than that of the VSOP in size. The surface accuracy of the receptive antenna, however, will be required at least 2 order of magnitude higher than that in VSOP since the parabolic surface of the VSOP is controlled to maintain within the small displacement of 0.1mm. It is indicated that additional difficulties are found by the VLBI of millimeter range at present.
ANTIMATTER REQUIRED FOR MODIFICATION OF ASTEROID ORBIT
For small asteroids, the interceptors loaded with the antihydrogen can destroy them completely. If the asteroid is too large to be entirely exploded, it is necessary to penetrate into the celestial body and blast off the surface materials effectively. It is estimated in the case of orbital change using explosion that the energy utilization efficiency is less than 1% i.e. the ratio of the exploded mass to the remaining mass of the asteroid.
The antimatter-matter annihilation generates shock wave and produces high energy plasma at the center of the explosion. If the plasma dissipates its energy to surrounding materials efficiently, lava with high energy will be blasted off. The reaction against the astereid produces the thrust. The energy E generated by the annihilation is related:ρ : asteroid density
r : diameter of lava region ( depth of penetration )
M : asteroid mass
ΔVmelt : effective velocity corresponding to melting energy
U : mean velocity of lava
The first term of the right hand side of Eq.(3) represents the internal energy and the second one does the kinetic energy of the lava. It is assumed that a half of the lava blasts and contributes to the orbital modification, and the rest half merely heats up surroundings. The velocity change V and the efficiency η are calculated:
The radius r is a control parameter of the explosion (or thrust generation). Choosing r so as to maximize the efficiency:
are obtained as the optimum velocity change and penetrating depth. For example, the optimum depth is estimated to be 240 m from Eq.(7) for the antihydrogen of 1 kg.
Figure 3 shows the relation between the mass of the antihydrogen and the delta-V calculated from Eq.(4). A value of 1m/s is the minimum delta-V required for the orbital change if the orbit is modified at 1.3 a.u. distance from the sun. Generally, the minimum delta-V is a function of the orbital elements, the direction of the thrust and the distance from the earth.
The closest distance between the earth and the asteroid is plotted in Fig.4 with thrusting directions as parameters. The optimum direction is either parallel or anti-parallel to the orbiting direction of the asteroid. The delta-V at ϑ=π/3 is ten times as high as that at ϑ=0 for given distance.
Figure 5 shows the closest distance as a function of delta-V on deorbiting position as parameter. The delta-V required for 1.55×108km is ten times as large as that for 2×108km. As the farther distance the orbit is modified, the smaller the delta-V is required. This means the importance of the early detection and the orbital modification as soon as possible.
At present, antiprotons are generated by the method of a collision between a heavy metal target and a proton beam which is accelerated up to several tens of GeV or more. Reference 8 reports that 1011 antiprotons (~pg) are obtained per hour in Fermilab. The productive amount of the antiprotons has been increased at the rate of 10 times per 3.5 years ever since the discovery by Segre and Chamberlan so that the antiproton will be available industrially in 2020's if it monotonically increases (sadly, this did not happen). It is necessary that the antimatter is stored as solid antihydrogen at cryogenic temperature since the antimatter required for the orbital modification amounts to the order of kg or more as seen in Fig.3.
The storage processes are shown in Fig.6. At first, the produced antiparticles are cooled by stochastic and electron coolings because antiprotons are tremendously hot Just after they are generated by an accelerator. They are decelerated as slow as several keV and are turned into the antihydrogen by three body recombination with cold positrons. The unrecombined particles are cycled in the antiproton and positron rings being collimated with accelerator and electrostatic lens. The resultant antihydrogen beam is decelerated and trapped by means of laser cooling. A vacuum ultraviolet CW laser for the hydrogen cooling have not been accomplished yet, but will be put to practical use in near future with stable multi-ionized ion sources recently accomplished. Solid antihydrogen is produced from the trapped antihydrogen, and is stored electrostatically.
Experimental demonstration is in progress with respect to the recombination and the deceleration of the antihydrogen. The antihydrogen is simulated by ordinary matter argon in the experiment, since antiparticle can be regarded as particle with opposite charge without annihilation. Except for the differences in the mass and the energy level for the laser cooling, the argon in a metastable state has the advantage of being incorporated with laser diode, which has energy level related to near infrared range. The photograph of the experimental apparatus is shown in Fig.7. It consists of a plasma source which simulates a low energy antiproton beam, a recombination chamber, a cooling and trapping chamber.
ANTIMATTER FACTORY AND INTERCEPTOR BASE
Necessary conditions for establishing the antimatter factory and the interceptor base comprises;
1: Sufficient solar power can be easily obtained,
2: Energy to launch the interceptor is small,
3: The earth's safety is assured at an accident.
The construction of the factory farther than the Mars orbit from the sun is not beneficial since the SPS (Solar Power Satellite) collects solar energy to produce antimatter. Lagrange points of L4 and L5 between the sun and the earth have the advantage of the minimum launching energy since they are the points of the gravitational equilibrium. It is also convenient from following stand-points to construct the plant on the back side of the SPS. First, the plant is cooled down as cryogenically as the space back ground temperature of 3 K because of isolation from the solar energy flux. Second, the high vacuum environment keeps the loss rate of the stored antimatter low because of low background density, a few particles per cm3. Even if the disaster by the annihilation occurs in the plant, the irradiation from the antimatter factory remains as low as several times of natural level at the earth with 150 million km (1 a.u.) distance between the earth and the plant.
Next we estimate the antimatter fuel to be changed in the interceptor. Suppose the interceptor encounters the asteroid at 200 million km from the sun in 30 days after launch. The necessary delta-V is about 30 km/s when the interceptor is launched in the same dlrection as the earth evolution, and about 90 km/s in the opposite direction. As for the latter mission, it is impossible for chemical rockets because of large payload mass ratio of 109. However, antimatter engine enables such a mission since the specific impulse can be chosen just like electric propulsion and the thrust density is as high as that of the chemical rocket. Forward indicates that the payload mass ratio of the antimatter rocket do not exceed 5.
The mass of the vehicle, m is assumed as 1 ton including an apparatus for the antimatter storage. Energy utilization efficiency ε by the antimatter-matter reactions is assumed as 0.32. The necessary antimatter is given bymv : mass of vehicle included an apparatus for antimatter storage
ma : mass of antimatter propellant
ε : energy utilization efficiency by annihilation
ΔV : mission delta-V
c : speed of light
Substituting ΔV=90km/s into Eq.(8), the required amount of the antimatter is 0.1g at most, which is negligible compared with that for the orbital modification of the asteroid. The mass of the reaction fluid is 4 ton. Consequently, the launching from the antimatter base located on the Lagrange points is possible. The earth protection system is schematically shown in Fig. 8.
First, necessity of the earth protection system against the meteorite collisions is investigated. The designed system consists of the VLBI radar tracking system, the antimatter plant and the interceptor to modify asteroid orbits. The radar tracking an asteroid by means of VLBI is feasible considering the state of arts of required technology. Some issues of millimeter wave remains open. An experimental simulation for the antimatter storage is introduced. It is desirable to construct the antimatter plant and the interceptor base combining the SPS at the Lagrange point. Destruction or orbital change of asteroids is concluded to be impossible without use of the annihilation energy.
At a spaceport, bulk cargoes can be launched with huge mass drivers. People and cargo can also be boosted into orbit using laser launch systems. Both of these can be used as ground-to-space weapons powerful enough for a planetary fortress. The Launch Guard controls these installations [a] to ensure terrorist do not hijack them as impromptu terrorist weapons of mass destruction and [b] to officially re-purpose them as weapons of mass destruction in order to wreak death and obliteration on any invading enemy spacecraft that unexpectedly appear.
If a spacecraft is on a collision course with something valuable or full of innocent bystanders (like the spaceport), or behaving erratically or suspiciously, the on-duty Launch Guard Range Safety officer will spring into action. They will trigger the off-course ship's integral self-destruct device or use surface-to-space weapons to blast it into smithereens. The range officer will have the agonizing task of weighing the lives on the ship with the lives at the projected impact point.
If civilian owned spacecraft have propulsion systems frightful enough to be weapons of mass destruction then by law all such ships will be equipped with destruct devices controlled by the launch guard. Just in case a tramp freighter with an antimatter engine has a drunk pilot and starts heading towards a major metropolitan area.
If the destructive energy is from the wayard ship's engine (e.g., antimatter) the self-destruct charge will just have to neutralize the engine. But if the destructive energy is the ship acting like an impromptu kinetic energy weapon, the closer the charge can come to vaporizing the entire ship the better.
Most real-world boosters and spacecraft include self destructs to prevent lawsuits and massive negative publicity if the rocket goes off course. Manned rockets generally have some sort of launch escape system to propel the habitat module clear of the blast radius (with the notable exception of the Space Shuttle).
The range safety officer with their finger on the big red button are usually located at some distance from the object they are blowing up. So they will have some objectivity (i.e., not hesitate because they are scared of committing suicide).
Huge solar power stations (SPS) can power MagBeams to push little spacecraft in near orbit or to give them a kick to another planet.
SPS can also power titanic laser arrays used for beam-powered propulsion for laser-thermal spacecraft all over the solar system. Especially since non-beam powered solar sails can only do about 3 milligees and you need at least 5 milligees to be practical.
They can also launch laser sail spacecraft on interstellar missions.
Such stations would be valuable and useful pieces of space infrastructure.
All of these provide advantage to people using spacecraft, but with the cost of being at the mercy of whoever owns the SPS. Ship captains have to file their flight plan with the SPS, and have to follow it to the letter or the beam cannot stay focused. And if your bill isn't paid up Beams-Я-Us will pull the plug. Sure Beams-Я-Us will need massive investments to construct the powersats and laser arrays, but it will be quite lucrative.
But then there is the awkward fact that a beam which could power a freighter far away in the asteroid belt is also powerful enough to vaporize a battleship in nearby cis-lunar space. Not to mention that any space garbage scow could suddenly become a laser spitting death machine with only the support of a powersat and a few half-silvered mylar balloons used as laser combat mirrors. You will have Powersat Weapons. The military will not be happy...
...Unless the military owns and operates Beams-Я-Us.
Naturally this can quickly turn into a Mutual Assured Destruction situation once there are more than one nation in the beam business. Which could sabotage efforts for the first beamsellars to get established. Solar power stations are such big targets and so very fragile. If any of the myriad nations of Terra felt threatened by the construction of a laser station, they could take out the billion-dollar station with only a sounding rocket and a bucket of gravel. There might have to be an international treaty forcing three or more nations to build large solar-powered laser arrays simultaneously.
In Rocheworld by Dr. Robert E. Forward the military had a series of such laser stations around Mercury. Given the plentiful solar energy each station could crank out a laser beam that was about 1.3 terawatts.
In Larry Niven's "Known Space" series, the warlike alien Kzinti gleefully attack our solar system, knowing that the pacifistic humans had no quote "weapons" unquote. This disaster was called the Kzinti Lesson. Among other things the Kzinti discovered the hard way was the fact that even though terrawatt lasers arrays used to push interstellar lightsail probes are technically "propulsion systems", nonetheless they can vaporize Kzinti warships like ants under a magnifying glass on a sunny day.
G. Harry Stine's (writing as Lee Correy) wrote a rocketpunk novel called Manna. In the novel, the military branches of the space-faring nations would like to put five gigawatt High Energy Laser (HEL) satellites in orbit. Using fancy techniques they are powerful enough to get their weapon laser beam through Terra's atmosphere and incinerate targets on the ground.
The trouble is the militaries want the HEL beamer satellites to be stealthy. The root of the trouble is that a five gigawatt HEL beamer containing a +five gigawatt power source is about as stealthy as a New York 4th of July fireworks display.
If only the power source could be at some distance from the HEL beamer, sending the energy by electromagnetic waves. You know, the same way a powersat sends microwave energy to ground power stations... hmmmmmmm.
That would work, the HEL beamers could be stealthy little dastards with no nuclear power plant, but rapidly unfurling a powersat reception antenna when it came time to zap something.
Now comes a bigger problem. Nobody can build any powerstats.
Why? Well, no corporation is going to embark upon a multi-billion dollar project like a powersat without insurance. And no insurance company is going to underwrite a multi-billion dollar installation which becomes a military target the instant it redirects its power beam from a power station in order to energize a HEL beamer. Especially a military target so huge, easy to hit, and incredibly fragile as a powersat.
How to solve the problem? Well, since it is an insurance problem, there should be an insurance solution.
Through a series of international agreements, the Resident Inspection Organization (RIO) was formed. This international group regularly inspected all powersats, and insured that they stayed pointed at ground power stations. In exchange, the insurance companies would underwrite the powerstats. If any powersat started to energize something that might be a stealthed HEL beamer, RIO would sound the alarm to all the astromilitaries, presumable giving the military units enough time to blow the living snot out of the powersat.
Naturally the astromilitary of Nation Alfa would be angry at RIO squealing when astromilitary Alfa tried to energize one of their HEL beamers. But astromilitary Alfa would be vary grateful if RIO squealed about astromilitary Bravo, Charlie, Delta or Echo doing the same thing.
If you are trying to establish a base or colony on a moon or other terrestrial body, you've got a problem. Such installations will require thousands if not millions of tons of pre-fab structures and support material. The tyranny of the rocket equation is going to make establishing the base more expensive than a mobster loan shark, because every gram counts.
This would be a perfect place to use in-situ resource utilization. But it is one thing to roast some gypsum to obtain some water. It is quite another to use local ores to create electronics and pressurized domes. Its not like there is a machine you can shovel dirt in one end and get habitat modules and stuff out the other.
Or is there?
Enter the Santa Claus Machine. You actually can shovel dirt in one end and get hab modules out the other. As long as all the chemical elements you need for the module can be found in the dirt. Such a machine will be priceless for creating planetary bases and spaceports.
But the trouble is such a machine can be a little too useful. It can make other stuff, like nuclear weapons, artillery lasers, unstoppable robot armies, and whatnot. Not to mention small items like undetectable counterfeit money. Heck, even the disassembler input stage is bad enough. It can quickly and easily turn tons of uranium ore into a lovely set of weapons-grade highly-enriched subcritical uranium ingots and a pile of waste uranium.
Blasted Santa Claus Machine is worse that a beam-propulsion array powered by a titanic solar power station. Unbelievably useful, but not the sort of thing you want in unsupervised civilian hands.
Well, lets use the same solution. Have them controlled by the military. Just like we have the Laser Guard in control of beam-propulsion arrays, we can have the Santa Guard in control of Santa Claus Machines. Also known as "Santa's Little Helpers."
So at the site of the proposed new base, the Santa Guard will emplace one or more Santa machines, and construct a secure housing where they can be kept under armed guard. The construction crew will submit blueprints to Santa Guard. The Santas will closely examine the blueprints to make sure they are not for weapons of mass destruction or other contraband, and supervise the printing. They will also be on the lookout for sub-units in several separate print runs that might be cleverly disguised components of a contraband item.
And in cases of illegal blueprints or illegal output, the Santas will do their best to arrest and bring to justice those who have broken the law.
Sovereign nations almost invariably impose controls on the import and export of trade goods (unless the nation is a freeport or something). The controls kick in when trade goods cross a magic line called the customs border. The border is patrolled by that branch of the civilian military called the Customs: collecting tariffs, halting or confiscating contraband, and apprehending smugglers.
If the custom border is located inside a spaceport, patrolling the boarder is the responsibility's of ground-based (or space station based) custom service. But if the custom border is drawn around the entire planet at orbital height, or even around an entire solar system / interstellar empire, then the job belongs to the space branch of the customs agency.
The primary difference is that the spacial branch zooms around in cutter-class spaceships, instead of wearing out shoe leather walking around the 'port.
Naturally the former branch is a bit more … exciting. Ground custom agent's main excitement is seeing the ship's captain break out in a cold sweat when you discover something irregular. By contrast space custom agents never know when that innocuous blip on the radar screen might abruptly turn into a life-or-death running gun-battle with a heavily armed smuggler spacecraft.
Ground customs also never know the gut-wrenching terror when a seemingly routine board-and-search operation turns deadly. Ground customs might not bother to carry sidearms, but space customs agents on a boarding mission invariably do. Otherwise they are just giving potential smugglers free hostages.
Ground customs agents just have to pound the pavement keeping an eye on the few openings in the spaceport's custom border. Space customs, on the other hand, may need to maintain constant deep space patrols of the huge border surrounding the planet/empire/whatever. The ease of the task depends upon the range and discrimination ability of the custom ship sensors.