Support Ships:
SSTO lander / Hypersonic Cruise Aircraft

Obviously landing our starship would not be practical. It could generate enough thrust to do it, but it would vaporize anything underneath it! So we need some support craft to commute from the Main ship to planets, moons, or anywhere else of interest. These would be in two specialized types. One (shown above) that can fly in an atmosphere, and another that's more at home in vacuum. This doesn't mean that they can't each fly in one anothers realms. The Vac. craft I'll describe has enough power to slow down to a crawl, and slowly let itself down through the atmosphere; and the aero craft can certainly manage a small moon with its onboard reaction mass. But that would not be an effective use of either craft.

Vacuum Lander and Support Craft

One of the Bussard papers described a SSTO craft 120' long, with 500 ton in-orbit mass, 20% payload. That could get to Mars in 40 days. It had surface to orbit reaction mass fractions of 38-48%. Rockets of thrust to mass of (0.2-10,000)/(Isp of 1500-1,000,000). I.e thrust-to-weight of 0.01 with specific impulse of 1,000,000. To a T-to-W of 10 with a Isp of 1,000. Very capable of taking off and landing on an earthlike planet and doing extensive cruising in a solar system. I used the theoretical description as the basis of the Vac. craft.

Mass numbers
Cargo50 tons +
Reaction mass500 tons max capacity.
200 tons needed to reach orbit from 1 g world.
442 tons needed to land and take off on 1 g world.
Hull & systems80 tons
engines120 tons
total450 - 750 tons

Light Vac Lander DimensionsStandard Cargo Pod Dimensions
42 meters (138 feet) long27 meters ( 88 feet) long
16 meters ( 53 feet) wide5.5 meters ( 18 feet) wide
9 meters ( 30 feet) high5. meters ( 16.5 feet) high

Since the vacuum landers need enough on board reaction mass to land, and take off, and possibly self deploy to the target moon or world. Cargo and reaction mass numbers can vary wildly depending on local gravity and mission. For example: the worst case would be traveling to a 1 G moon, landing, and returning to orbit with 50 tons of cargo. This is an extremely unlikely scenario. Requiring up to 500 tons of reaction mass.
The best case would be to land or orbit a 265 ton load to a destination with a tanker with reaction mass. In either case only 38% of gross weight would need to be reaction mass.

Aero Lander

For a aerodynamic shuttle that can get to orbit you have the advantage of being able to use the air as reaction mass. You might be able to get all the way to orbital velocity in the atmosphere this way. But the atmospheric hull drag (and heating) gets pretty bad at high mach numbers. (Earth orbital speed is about mach 24 or 18,000mph.) So most researchers come to the conclusion its probably more practical to use atmospheric reaction mass for atmospheric cruising and initial boost, and then switch to super-heated steam rockets at low mach speeds. Still that does allow a very effective craft.

Such a air breathing lander could use (when possible) the atmosphere of the target planet as the reaction mass for low speed to hypersonic travel between surface teams, and then exit the atmosphere to do the rest of the acceleration with pure rocket power using stored reaction mass. Saves a surprisingly large percentage of the reaction mass. I used to work with space shuttle flight planners. In conversations they emphasized that almost all of the fuel and reaction mass is required for initial acceleration of a launch vehicle. The shuttle for example burns half its fuel getting to Mach 6 (about 1/4th orbital velocity) and three fourths by Mach 12.

For example assuming a very poor specific impulse of 2500, Froning gets:

Rocket start MachReaction massengine massHull & PayloadSystemsGross Take off Mass
051.7 tons29.4 tons28.811.8122.2 tons
6-103018.52311.885 tons

So using the atmosphere can cut about 42% out of the reaction mass needed and cut about 30% out of the gross takeoff weight. With proportional cuts in the crafts empty weight and size. Given that manufactured items cost is roughly proportional to their dry weight (assuming everything else about the craft is proportional). Assuming a $1000 per pound purchase price for these craft. They would cost $80 to $70 million respectively.

Note however that air breather engines of thrust to mass of 6-12, with a specific impulse of 2000-4000 were considered possible.
I decided to design the aero craft in a form similar to one of the Air Forces new "Aurora" craft. In case you haven't heard of them, "Aurora" is the name of a class of top secret hypersonic air craft the Air Force is trying out. The reason its become such a well known secret is that its hard to test fly any weird looking craft without people noticing it coming and going. This particular one is even harder to hide, since its extremely loud, big, diamond shaped without wings or fins, and covered in what looks like Shuttle tiles. Not to mention that people who see things streaking overhead at 4000 - 5000 mph, remember and talk about them. Especially when such people are the air traffic controllers at Los Angeles LAX airport!

The assumed reason for the weird diamond shaped cross section, is to let the hull function as an efficient external burning Scramjet/Ramjet engine. At speed the hypersonic shock wave flows on the front of the hull up to the 'fold line' (or whatever its the widest point is called). Fuel is sprayed into the airstream and burned just past the fold line. The heated air then expands between the hull and the rear shock wave. This expansion area acts like a rocket nozzle.

What I was thinking is that if your rockets exhausted just past the fold line they could at least get increased thrust by using the rear hull for a larger expansion volume. Similar to a plug nozzle rocket. When flying in an atmosphere, the heat from the rockets would heat and expand the air around the rear of the ship. Using it as an extra reaction mass. You could even cut the rockets entirely and just heat the air directly with plasma arc's or relativistic electron beams at the fold line. This would let you save your internal reaction mass for later. (see image above and diagrams below)

I'm assuming water as a stored reaction mass/heat sink (isn't water wonderful). Water weighs 62 lb per cubic foot. So a 100 tons of water fits in 3226 cubic feet. I.E. a cube 14.78 foot per side. The volume shown for the are lander is 9700 cubic feet allowing up to 300 tons of reaction mass. Which should be very generous for extended vacuum operations, or landing and then taking-off from a planet.

The layout of the internal components is rough, but obviously allows enough room for what we need. The cargo bay is the same size as in the new McDonnel Douglas C-17 military transports (thou I've assumed about 20 tons more cargo capacity). I figured if the C-17 can haul around tanks and armored personnel carriers. The same volume should be good enough for planetary exploration.

Mass numbers
Cargo100 tons
Reaction mass300 tons max capacity.
200 tons needed to reach orbit from 1 g world.
442 tons needed to land and take off on 1 g world.
Hull & systems110 tons
engines90 tons
total450 - 750 tons

Aerodynamic Lander DimensionsCargo Bay Dimensions
50 meters (165 feet) long27 meters ( 88 feet) long
30 meters (100 feet) wide5.5 meters ( 18 feet) wide
6 meters ( 20 feet) high5. meters ( 16.5 feet) high

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