Spaceship concepts from The Dream Machines

[cjackson]

How plausible are these concepts?

Thomas Ciesla's Centauri project utilizes a terraformed asteroid with antimatter propulsion that can travel at .30 c

Alan Holt's interstellar transport system uses two field generators and 16 field amplifiers to create a space-time bubble around a vessel

Giles Primeau's Heracles project uses muon catalyzed nuclear fusion propulsion and can reach Mars in 3 days. It uses negative muons for lower temperatures and has an isp of 1 million seconds with the ability to accelerate 1g.

Charles Orth proposes an inertial confinement fusion vehicle named VISTA. I has many high energy lasers mounted around the surface of a cone with mirrors directing beams to the detonation site at the apex. Pellets of deuterium, tritium, and hydrogen are ejected into the focus where they are detonated creating high energy plasma directed by the drive coil's magnetic field. .02 g acceleration or greater is possible and VISTA can reach Mars in 45 days. John Callas has an antimatter variation that is 1 kilometer wide and utilizes protons and antiprotons. This vehicle can make Epsilon Eridani in 100 years.

Gary Hudson's solar system spaceship is single stage reusable vehicle that will operate like a commercial aircraft. It's payload is 20 percent of gross weight. It powered by an advanced fission/fusion pulse engine, and has a composite material pusher. Propellant will be water heated by pellets of either 238u/235u hybrid or 238u/LiD/239pu layered capsule or antihydrogen that are detonated by an electron or heavy ion beam. In the atmosphere the vehicle launches with VTOL tip driven lift fans. After ascending to 30,000 ft the scramjets ignite, and at mach 1.2 the vehicles begins to climb. The scramjets stop when the craft is moving at 11,000 ft/sec as it coasts to orbit where the nuclear engines activate.

A. Bond proposes the Ram Augmented Interstellar Rocket which can accelerate to .20 or .30 c. Interstellar protons act as the reaction mass, with a small fraction used for the ships lithium-proton reactor.

Robert Enzmann's fusion-powered vessel is powered by 3 million tons of super-cold deuterium in a metal sphere that is 1,000 feet in diameter. The sphere will act as a radiation shield for three crew modules behind it. Each will be 300 feet long and 300 feet in diameter. They will have 20 decks and 100 rooms each, with portions of the modules able to rotate to produce artificial gravity. The craft is 2,264 feet long overall. Behind it are 24 fusion engines able to accelerate the vessel to .09c. Alpha Centauri can be reached in 60 years.

 

[Ryan_m_b]

Perhaps you should post some links to what you are referring to. The biggest problem with space propulsion (ignoring every other problem, many of which make propulsion look trivial) is the energy needed. Antimatter has the best speculative specific impulse of around 1,000,000 isp. This means that with a 1:1 mix of fuel to ship it can accelerate at 1g for 1,000,000 seconds (~11.5 days IIRC) achieving a top speed of 10,000km per second or 0.03c.

The main problem with this is threefold:
Antimatter production - it's the most costly material at tens of trillions of dollars per gram and currently can only be made a few particles at a time
Antimatter storage - record is just 1000 seconds
The danger - for even a moderate mass ship of 1,000 tonnes you would need 250 tonnes of antimatter which gives you about as much destructive power as ~350,000,000 Hiroshima bombs or to put it another way ~100,000 Tsa Bomba's (most powerful nuclear bomb ever).

As for the speculative proposals like making a "bubble of space time" that really doesn't make any sense. The only thing that comes close is the proposed Alcubierre warp drive and that requires impossible materials and energy levels. The ramscoop design is also unviable due to the low concentrations of interstellar hydrogen and the muon catalysed fusion assumes huge jumps in our current science.

Out of all of them the only slightly viable idea I see is Orth's and Enzmann's any even those are only potentially good if we develop science, technology and industry orders of magnitude greater than what we have now. They also ignore the problems of space travel beyond propulsion that are far harder (my favourite one to champion being the creation and maintenance of a stable ecology).