Illustrations by Dennis Martin based on designs by Dave Dietzler

This ship consists of four ETs amassing 30 tons each. Total 120 tons+25 tons reactor shield, 5t NTR, 25t solar flare shelter, 45t (LSS, fuel cells, thrusters, crew, etc.)=220 tons If the three LOX tanks at the stern and the two LH2 tanks to the sides are filled with LH2, 340 tons of it, the mass ratio will be 2.545.  With a 1000 second NTR the ship could reach 9.15 kps.  The only problem is keeping that LH2 cold.  The tanks are not that well insulated.  If water, easily stored for long periods without boil-off,  is used the ship will have a MR of 22.  That's not possible on Earth but it is possible to build a ship with a MR that high in space. If the NTR runs at 5000 F. it will yeild an ISP of 450 seconds with water and achieve a delta V of 13.66 kps.  That's better than LH2! Water will be the propellant of choice for flights between Earth, the Moon and Mars.  Out around Saturn the problem won't be boil-off but just the opposite.  Water might freeze unless we heat it with some kind of heat pipe system from the NTR(nuclear thermal rocket) motor.  Methane, CH4, which is abundant in the atmosphere of Titan could be used for propellant.  It liquefies at -260 F. and it's about -300 out around Saturn.  The density of CH4 is 0.42 or a bit less than half as heavy as an equal volume of water.  The spaceship above will have a MR of 9.73 if loaded with CH4.  Methane will yeild an ISP of 560 seconds.  Thus, a total dV of 12.5 kps is possible with methane.  If we go out as far as Uranus or Neptune we might even have to warm the methane with heat from the NTR to keep it from freezing at -300 F.!

Another ship with nuclear thermal propulsion. This one amasses about 175 tons (#2 ETs plus #2LOX tanks plus 100 tons fittings) With the three stern LOX tanks full of H2O, the ship has a MR of 10.43 and a total dV of 10.33 kps with a 450 second ISP.  That's more than enough for flight from LEO to LO or  L1 and back.  It's enough for flight to Mars in less than 180 days and for getting around amongst the moons of Saturn.  Like the ship above, this ship has 550 cubic meters of space in the forward LOX  tank and 3000 cu.meters in the two 1500 cu.mtr. LH2 tanks for a total of 3550 cubic meters.  That would be roomy enough for a crew of 30+ With CH4 this ship will have a MR of 4.86 and a dV of 8.67 kps.

This ship has a much interior volume as the two previous ships but just one LOX tank at the stern. It amasses 160 tons (#2 ETs plus 100 tons fittings) With that tank filled with water, this ship has a MR of 4.44 and can reach 6.57 kps with a 450 second NTR.  That's just enough for flight from LEO to LO or L1 and back to LEO with retro rocket braking.  If it used LH2, it would have a MR of only 1.25 and it could only reach 2.18 kps.  Water is far better than LH2! On CH4 this ship has a MR of 2.4 and a dV of 4.82 kps.  CH4 also beats LH2. Not bad.

These vessels feature centrifuges for "artificial gravity" at about 1/6th G.

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