What about the idea of a manned vehicle to travel quickly from lunar orbit to Mars orbit and back with acceleration of 1 G half way, followed by deceleration of 1 G (thereby providing artificial gravity during flight), using a huge inflatable parabolic foil solar concentrator to superheat water propellant, eliminating the need for chemical fuel other than for RCS maneuvering?
Solar concentrator steam rocket
- Thread starter Bill Morris
- Start date
Would it really do that much good to get rid of fuel, when you still have to haul the propellant along?
Using sunlight rather than fission power to heat the propellant might save slightly on mass and complexity - or then increase those, as the mirror and its aiming systems wouldn't be trivial to implement. If you can do the mirror, you could probably also do a lightsail, which wouldn't give you 1G but would be more efficient overall (thus allowing you to have a proper centrifuge as the payload).
Also, water might not be the propellant of choice, unless you got it aplenty from the Moon somehow. Something easier to store in a liquid or easily liquified state might be preferable to a big block of ice.
Timo Saloniemi
Using sunlight rather than fission power to heat the propellant might save slightly on mass and complexity - or then increase those, as the mirror and its aiming systems wouldn't be trivial to implement. If you can do the mirror, you could probably also do a lightsail, which wouldn't give you 1G but would be more efficient overall (thus allowing you to have a proper centrifuge as the payload).
Also, water might not be the propellant of choice, unless you got it aplenty from the Moon somehow. Something easier to store in a liquid or easily liquified state might be preferable to a big block of ice.
Timo Saloniemi
Even if we had a means of producing anitmatter in quantity and advanced storage bottles for it, propellent would still be required. Hydrogen is the most efficient for propulsion, but it's easier and more reliable to use water.
This kind of system could be used first to transport equipment and provisions before humans make the trip and give us opportunities to work out any bugs and be sure it's safe enough for human travel. And such test/supply vehicles left in Mars orbit could serve as a supply of propellent and spare parts for any return trips.
And no, water is not a chemical fuel in this context, just propellent.
I looked at the Wikipedia article cited above before posting, but what I'm proposing not quite the same. I'm saying build something big, simple, cheap, and ugly that makes the trip fast enough to minimize negative effects on human health and able to maintain artificial gravity on the way. Having to carry conventional fuel means needing more fuel just to transport the fuel. I say let sunshine be your fuel. It just takes a huge mirror to grab enough of it to get the job done.
It could be done going back and forth to the moon first just to get used to this method and improve the engineering details before taking a crack at Mars.
This kind of system could be used first to transport equipment and provisions before humans make the trip and give us opportunities to work out any bugs and be sure it's safe enough for human travel. And such test/supply vehicles left in Mars orbit could serve as a supply of propellent and spare parts for any return trips.
And no, water is not a chemical fuel in this context, just propellent.
I looked at the Wikipedia article cited above before posting, but what I'm proposing not quite the same. I'm saying build something big, simple, cheap, and ugly that makes the trip fast enough to minimize negative effects on human health and able to maintain artificial gravity on the way. Having to carry conventional fuel means needing more fuel just to transport the fuel. I say let sunshine be your fuel. It just takes a huge mirror to grab enough of it to get the job done.
It could be done going back and forth to the moon first just to get used to this method and improve the engineering details before taking a crack at Mars.
10 tons of water and 10 tons of propellant weigh the same.
And when you get out past the orbit of the Earth, the power of sunlight starts to drop off dramatically; your solar mirros would have to get bigger and bigger the farther out you go... hence the need to use nuclear-power on any probes going out from the Earth orbit.
And when you get out past the orbit of the Earth, the power of sunlight starts to drop off dramatically; your solar mirros would have to get bigger and bigger the farther out you go... hence the need to use nuclear-power on any probes going out from the Earth orbit.
There's no way steam propulsion could give you anywhere remotely near a continuous 1G acceleration, certainly not for the time it'd take to get from Luna to Mars. For a ship with half the mass of the space shuttle (i.e. 50 tons), you could get less than a hundredth of a gee with a solar thermal engine.
A drive using water as reaction mass could certainly be a convenient low-thrust propulsion system, since it would be quite lightweight and the propellant would be easily obtainable. But it's not viable for high accelerations. You want artificial gravity? Build the ship with a rotating section.
A drive using water as reaction mass could certainly be a convenient low-thrust propulsion system, since it would be quite lightweight and the propellant would be easily obtainable. But it's not viable for high accelerations. You want artificial gravity? Build the ship with a rotating section.
All Seeing Eye
Admiral
Now I dont mean to sound like an idiot, although I probably am one when it comes to Science 
but I have question:
Lets say we take a lump of radioactive material and its decaying and giving off gamma radiation, can the gamma rays be deflected using an EM field? if so would it be possible to place a radioactive substance on the back end of a rocket and using EM fields deflect all the gamma radiation out the back of the rocket producing some kind of thrust? for say a sattelite?
but I have question:Lets say we take a lump of radioactive material and its decaying and giving off gamma radiation, can the gamma rays be deflected using an EM field? if so would it be possible to place a radioactive substance on the back end of a rocket and using EM fields deflect all the gamma radiation out the back of the rocket producing some kind of thrust? for say a sattelite?
No, EM fields do not deflect gamma radiation, because gamma rays are EM radiation themselves, just a very high frequency of light. EM fields only deflect charged particles (protons, electrons, atomic nuclei).
^^What you're talking about is essentially an electron beam. For particle beam propulsion, the best model isn't generating the beam from the ship itself, which would require dragging a lot of massive machinery along with the ship, but firing a beam from an orbital station and pushing the ship by deflecting the beam off of a magnetic sail. The sail can also be used to decelerate the ship by interaction with the solar wind (or interstellar medium, depending on how far the ship is travelling).
The advantage of beam propulsion, whether laser or particle-beam, is that the ship doesn't need to carry fuel or a large power source and can therefore be much lighter, able to accelerate faster. This is especially true of a magnetic sail, since a particle beam can impart very high accelerations. The solar thermal rocket proposed in this thread has a similar advantage that the energy source (the Sun) is external, although it does require onboard propellant and would thus be heavier and have a finite fuel supply.
The advantage of beam propulsion, whether laser or particle-beam, is that the ship doesn't need to carry fuel or a large power source and can therefore be much lighter, able to accelerate faster. This is especially true of a magnetic sail, since a particle beam can impart very high accelerations. The solar thermal rocket proposed in this thread has a similar advantage that the energy source (the Sun) is external, although it does require onboard propellant and would thus be heavier and have a finite fuel supply.
All Seeing Eye
Admiral
I thought that any kind of substance giving off huge amounts of radiation would produce some kind of thrust no matter how small and that by somehow causing all the particles given off during decay to be expelled out of a nozzle would create thrust in a 'single' direction which is why I suggested the EM field to try and deflect them all in the same direction. Could this not be done in any way at all? by defelcting all the beta radiation out of a nozzle? the EM field could be powered by a nuclear reactor in combination with solar cells and a solar sail for extra thurst from solar wind.
Yes, radiation does generate a small amount of thrust, which is how solar sails work. (They don't get thrust from solar wind as you say, but from the radiation pressure of sunlight itself.) But EM fields don't deflect EM radiation. If you want to generate a beam of EM radiation travelling in a single direction, you build a laser.
And I already addressed the question of how to use "beta radiation" (i.e. an electron beam) for propulsion. It's in my previous post.
And I already addressed the question of how to use "beta radiation" (i.e. an electron beam) for propulsion. It's in my previous post.
All Seeing Eye
Admiral
I was thinking more along the lines of an Ion Thruster but replacing the Ions with the radiation emitted from a radioactive substance, I didnt mean laser beams or electron beams fired AT the vehicle I was talking about the source of the thrust actually being on the vehicle itself, since a lot of radioactive substances have lengthy decay rates I imagined it would be a decent form of long lasting propulsion even if the thrust was only miniscule.
^^Yes, but as I explained, beams fired at the vehicle are better because the ships can be lighter and continue to be propelled for longer. I know what you meant, but there are many ideas out there that are much more feasible.
Here's a great page that lists quite a few proposed forms of spacecraft propulsion, although it doesn't include beam propulsion systems:
http://www.projectrho.com/rocket/rocket3c2.html
Here's a great page that lists quite a few proposed forms of spacecraft propulsion, although it doesn't include beam propulsion systems:
http://www.projectrho.com/rocket/rocket3c2.html
In just looking for ways to transport a lot of equipment through space without having to boost huge amounts of fuel into orbit from Earth, staying with the notion of that large inflatable mirror to capture a lot of energy from sunlight, what about using spring-feed rods made by sintering moon dust (with solar energy on the moon) as the reaction mass, so that a cargo ship would need conventional fuel only for RCS but not for its main thrusters? This would be mainly for transporting equipment and supplies to the moon, going back and forth between Earth orbit and lunar orbit.