Tailsitter Embarking

Embarking and debarking from an aircraft is relatively straightforward. You push a short set of steps up to the door and let the passengers go.

It is much more difficult with a tail-sitting rocket. Even more difficult if it occasionally lands on wilderness planets with no spaceports, launch towers, or other amenities. Compounding the problem is that if your rocket uses a fission reactor, you have to prevent the crew from receiving nasty doses of radiation while entering or leaving the ship.

If your rocket only takes off and lands from spaceports, this necessitates that the launch pads be equipped with launch towers that have elevators. The elevators can carry the crew and cargo to the loading hatches. You'd better include a way to move the tower away from the rocket before launch, especially if this is a nuclear rocket. The exhaust plume will violently terminate the tower's warranty. The rocket will be limited to landing at spaceports equipped with towers tall enough to reach the loading hatches.

Things get more difficult if you are landing on a wilderness planet. The obvious solution is a species of ladder set into the side of the rocket. The one in the movie Destination Moon had individual rungs that could retract when you needed the hull to be aerodynamically smooth. That must be a maintenance nightmare.

However, you are now limiting your landing party to only able-bodied crew people. The ladder on the Destination Moon ship "Luna" is about 23 meters (75 feet). When was the last time you climbed a ladder that was eight stories tall? If you break an arm or leg, you are stranded. And there is no way to transport any large amount of cargo.

These are all arguments for making belly-landing spacecraft.

In most rocket designs, the bottom edge of the hull is some distance above the ground due to the tail fins. This is generally to prevent the exhaust plume from splashing back onto the hull during landing. However, if your ladder is attached to the hull, the crew will have a problem with the gap.

In many SF images, they use an extenable attachment to bridge the gap, sometimes a rope ladder. In this scene from Destination Moon the crew carries down the lightweight extension. At the bottom of the hull they jump down to the ground, safe in influence of the weak Lunar gravity. Then they hook the extension onto the end of the hull.

The traditional way to deal with the cargo and wounded crew member problem is with a crane.

Belly Lander Embarking

The cargo problem is a good argument for spacecraft that land on their bellies. While it does make the arrangements inside the habitat module difficult, it makes it vastly easier to load and unload cargo. Cargo cranes are so inconvenient.

One of the draw-backs to a belly lander is that in the spacecraft in general, and in the habitat module in particular, the direction of "down" changes. Under thrust the direction of "down" is in the direction the exhaust is traveling, along the thrust axis. When landing on the ship's belly and while sitting on the ground impersonating an aircraft, "down" is at ninety degrees to the thrust axis.

This happened with the old NASA Space Shuttle.

There are ways of dealing with this.

Water Embarking

And if your ship is one of those specialized for water landing, embarking/debarking/load-unload cargo is a nightmare. A tail-lander floating at sea is going to have a large percentage of the body submerged underwater. It will not be able to get anywhere close to a shore-based wharf, not with its outrageous draft (draught). It will have to unload onto a free-floating wharf or a cargo naval vessel far away from the shore.

In this case it would make more sense to use some kind of belly-landing sea-worthy shuttle. That way you'll have a ship which has a small enough draft so it can float up to a wharf, quay, jetty, dock, or even a reserved berth; without ripping out the shuttle's belly on the jagged rocks on the harbor sea floor. The main ship can be a functional tail-sitter up in orbit.

Time for the Stars

(ed note: The good starship Lewis & Clark (L-C or "Elsie") is a torchship, and lands in the water. Otherwise its mass-converter powered torch drive would have the ship landing in a huge crater of freshly-created boiling lava. Also, since Elsie is exploring newly discovered planets, there will be no existing landing facilities. Landing in the smooth water is far safer than landing on uneven ground.

The mass coverter can use water or any other non-corrosive fluid as fuel. A "monkey island" is a nautical term referring to an open platform at the top most accessible height or an open deck directly above the navigating bridge, pilothouse, or chart house. In the Lewis & Clark, the navigating bridge is right at the top of the starship.)

When they left, I was on top of the Elsie glumly watching them get into the boats. There was a "monkey island" deck temporarily rigged up there, outside the airlock; it was a good place to watch the boats being loaded at the cargo ports lower down. Engineering had completed inspection and overhaul and had about finished filling the boost-mass tanks; the Elsie was low in the water and the cargo ports were not more than ten feet above waterline (naturally the more full the propellant tanks, the lower the ship sits in the water). It made loading convenient; at the time we put the first party ashore the tanks were empty and the boats had to be lowered nearly a hundred feet and passengers had to go down rope ladders—not easy for people afraid of heights, as so many are. But it was a cinch that day.

The airlock was only large enough for people; anything bigger had to go through the cargo ports. It was possible to rig the cargo ports as airlocks and we had done so on Inferno around Beta Hydri, but when the air was okay we just used them as doors. They were at the cargo deck, underneath the mess deck and over the auxiliary machinery spaces; our three boats and the two helicopters were carried just inside on that deck. The boats could be swung out on gooseneck davits from where they nested but the helicopters had to be hooked onto boat falls (a tackle used to hoist or lower a ship's boat from or to the davits), swung out, then a second set of falls hooked to them from the monkey island above, by which a helicopter could be scooted up the Elsie's curved side and onto the temporary top deck, where her jet rotors would be attached.

Mr. Regato cursed the arrangement every time we used it, "Mechanical buffoonery!" was his name for it. "I've never seen a ship's architect who wasn't happy as soon as he had a pretty picture. He never stops to think that some poor fool is going to have to use his pretty picture."

As may be, the arrangement did let the helis be unloaded with a minimum of special machinery to get out of order—which, I understand, was a prime purpose in refitting the ships for the Project. But that day the helicopters were outside and ready, one of them at camp and the other tied down near me on the monkey island. All we had to do was to load the boats.

The boats were whale boats molded of glass and teflon and made nonsinkable by plastic foam in all dead spaces. They were so tough that, while you might be able to bash one in, you could not puncture it with anything short of a drill or a torch, yet they were so light that four men could lift one that was empty. It did them no harm to drive them up onto a rocky beach, then they could be unloaded and easily dragged higher. They were driven by alcohol jets, just as the helis were, but they had oars and sails as well. We never used the oars although all the men had gone through a dry drill under my Uncle Steve's watchful eye.

From Time for the Stars by Robert Heinlein (1956)
The Prince

     They went through narrow whitewashed corridors, then into the bright Florida sunshine. A narrow gangway led to the forward end of an enormous winged landing ship that floated at the end of a long pier crowded with colonists and cursing guards.
     The petty officer spoke briefly to the Marine sentries at the officers' gangway, then carefully saluted the officer at the head of the boarding gangway.

     The ship circled the harbor, then glided in on its stubby wings to settle into the chop outside the breakwater. The waves were two meters high and more, and the ship rolled badly. One of the new recruits was sick. His seatmate handed him a plastic bag.

     Soon the shuttle moved into the inner harbor, where there were no waves, and everyone felt better. A lone tugboat came alongside and eased the spacecraft toward a concrete pier. There was no other traffic in the harbor except for a few small fishing boats.

     The landing boat fell away from the orbiting warship. When it had drifted to a safe distance, retros fired, and after it had entered the thin reaches of the planet's upper atmosphere, scoops opened in the bows. The thin air was drawn in and compressed until the stagnation temperature in the ramjet chamber was high enough for ignition.
     The engines lit with a roar of flame. Wings swung out to provide lift at hypersonic speeds, and the spaceplane turned to streak over empty ocean toward the continental land mass two thousand kilometers away.
     The ship circled over craggy mountains twelve kilometers high, then dropped low over thickly forested plains. It slowed until it was no longer a danger to the thin strip of inhabited lands along the ocean shores. The planet's great ocean was joined to a smaller sea by a nearly landlocked channel no more than five kilometers across at its widest point, and nearly all of the colonists lived near the junction of the waters.
     Hadley's capital city nestled on a long peninsula at the mouth of that channel, and the two natural harbors, one in the sea, the other in the ocean, gave the city the fitting name of Refuge. The name suggested a tranquility the city no longer possessed.
     The ship extended its wings to their fullest reach and floated low over the calm water of the channel harbor. It touched and settled in. Tugboats raced across clear blue water. Sweating seamen threw lines and towed the landing craft to the dock where they secured it.

     Lysander peered down through orange clouds. The ground was invisible, but cloud wisps streaked past, and stress diamonds formed near the wingtips of the landing ship. It was eerily quiet in the passenger cabin. Lysander turned from the viewport to his companion, a young man about twenty and much like himself. "Mach 25, I'd guess," Lysander said, then caught himself. "Fast. Faster than sound, Harv. A lot faster."

     The landing ship banked sharply, then banked again. Strange accelerations lifted the more than two hundred passengers from their seats, then slammed them down again. The ship turned, banked, turned again in the opposite direction. Lysander remembered the dry voice of his ground school instructor explaining that delta wing ships lose energy in turns. Lysander had certainly learned that on the flight simulator and later in his practice re-entry landings. He glanced outside. The landing boat had a lot of energy to lose before it could settle on one of Tanith's protected bays.

     Barton's binoculars gave him an excellent view of the stubby-winged craft as it settled in on the choppy water. It skirted the crimson waves where the nessies were fighting and sped across to the dock area at too high a speed, turning just in time. It had come full speed close enough to the pier to make Barton wince.
     "Hotshot," he muttered. Most landing boat pilots were.
     "Worried about nessies. I would be too," Honistu said.
     The Talin class was the smallest of the CD's assault/pickup boats. It looked fairly large, but most of its bulk was tankage and engines behind a small cabin and cargo area. The Talin class was designed to carry a marine assault section, two metric tonnes, to orbit, or bring twice that mass from orbit to ground. Its mission was to land troops in unexpected places.
     And that we've done, Ace Barton thought.
     Crewmen appeared at the aft hatches and caught lines thrown from the docks. The landing boat was winched in until it lay against the pier. The broad landing hatch opened.

     A crew snaked fuel lines out. A minute after they were connected up, they glistened with condensing frost. The fuel and oxygen lines crossed the road to the pier, and the ranch hands had put up a steel crossover to allow trucks to drive over them without pinching them off. Now a mixed crew of ranch hands and Barton Bulldogs was unloading crates from the trucks and carrying them aboard the landing craft.

From THE PRINCE by Jerry Pournelle and S. M. Stirling (2002)

Nuclear Complications

Things become vastly more complicated if the engine is radioactive. Due to mass considerations, the reactor is usually unshielded, except for a "shadow shield" which only protects the habitat module. When the crew start down the hull ladder, they will soon be exposed to the glow of deadly radiation. It might be worth the mass penalty to add some side shielding to protect the ladder. Or parts of the shadow shield could be rearranged.

When we stepped out of the little car it went back where it came from. In front of me was a ladder disappearing into the steel ceiling above. Dak nudged me. "Up you go." There was a scuttle hole at the top and on it a sign: RADIATION HAZARD-Optimax 13 Seconds. The figures had been chalked in. I stopped. I have no special interest in offspring but I am no fool. Dak grinned and said, "Got your lead britches on? Open it, go through at once and straight up the ladder into the ship. If you don't stop to scratch, you'll make it with at least three seconds to spare."

I believe I made it with five seconds to spare. I was out in the sunlight for about ten feet, then I was inside a long tube in the ship. I used about every third rung.

From DOUBLE STAR by Robert Heinlein, 1956

An interesting solution was in the old "B" movie Battle in Outer Space. Consider, if a girder is thirty meters long when it is vertical, it is still thirty meters long if horizontal. Say that thirty meters is a safe distance from the atomic drive in the ship's tail. Attach a thirty meter girder by a hinge on the atomic drive, and put an elevator cage on the other end. When the girder is vertical, the landing party enters the cage, a safe thirty meters from the drive. The girder then pivots on the hinge until the cage is on the ground. All this time the landing party is still at a safe distance. They then exit the cage onto the planet's surface. If the ship is streamlined, the girder and cage will be recessed into the hull, with the outer part of the girder covered by the ship's skin (you can see the recess hole in the middle picture above).

There was a similar arrangement in The Jupiter Theft by Donald Moffitt.

To the right is an 1961 design proposal by Douglas Missile and Space Systems for an atomic powered lunar lander, the radioactive propulsion unit is in the nose of the ship. This allows astronauts to exit the landed ship without going near the atomic pile.

Other Ideas


The engineer known as JanJaap has made a design trying to make the Battle in Outer Space solution actually work. The movie solution would require most of the interior of the ship to be filled with elevator machinery. JanJaap's solution uses cables instead, to create a collapsible tram way.


Deltapax had an alternate idea, to top-suspend the tram cable.

Promus suggested that the cable can be replaced by a sort of ratchet in the support.

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