Steam power in a rocket?

[larrison]

Okay, this may be a bad idea, how about a burn chamber (with a fuel that requires no cryogenics) that will heat up to about 2,000 to 2,500 degrees. The chamber could have heat dissaping fins to make use of more of the energy released. That chamber is nested inside a carbonfiber chamber and water is injected to produce thrust. I read somewhere that water turning to steam expands it's volime at least 14 times and depending on temperature cad go even higher. The whole system would be relatively cool and lighter than conventional engines.

 

[vogon13]

Something similar almost worked for Evel Kneivel.<br /><br />Check out Pluto Project for description of a nuclear ramjet (also not too far off what you're describing).<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[scottb50]

I think your first inkling was on the money.<br /><br />I can't see steam having near the thrust of a conventional engine and it would take a lot more water than you would use with LH2/LOX engines. Then the problem of the burner chamber. <br /><br />I can't imagine them being much lighter either, those old steam trains were pretty massive and they didn't get the water anywhere near that hot. <div class="Discussion_UserSignature"> </div>

 

[mlorrey]

Thrust can be quite sufficient, depending on the amount of heat you produce and how fast you pump the propellant. Putting your reactor into a near meltdown is all thats needed for high thrust.<br /><br />But thrust isn't the problem. Nuke engines can be made with a 20 to 1 thrust to weight ratio. Plenty of thrust. It is Isp that is the real concern, both getting off earth and place to place in space. Earth is the only gravity well worth visiting where high thrust is needed as well as high Isp. All the others can be visited with simple steam engines to get in and out, then using other electric systems at superhigh Isp to traverse space.

 

[scottb50]

To operate at temperatures that could produce a lot of thrust would require a great deal of cooling just to stay in existance. The amount of coolant, or water required would have to be huge. <div class="Discussion_UserSignature"> </div>

 

[mlorrey]

<blockquote><font class="small">In reply to:</font><hr /><p>To operate at temperatures that could produce a lot of thrust would require a great deal of cooling just to stay in existance. The amount of coolant, or water required would have to be huge. <p><hr /></p></p></blockquote><br /><br />No, it wouldn't. Water has immense thermal absorption properties, it could be used as coolant up to and even beyond the ionization point of water. Use as such has already been investigated for plasma/ion propulsion with positive results. Please don't make such empty statements when you haven't read the literature (scientific, not sf). Particularly read the reports on Project Pluto, among other nuclear proposals, such as Zubrin's Nuclear Salt Water Rocket:<br />http://www.npl.washington.edu/AV/altvw56.html<br />Or low pressure lunar water nuclear rockets:<br />http://www.neofuel.com/moonice1000/<br /><br />There are also reasonable proposals for testing nuclear propulsion here on earth safely:<br />http://www.lascruces.com/~mrpbar/SAFE%20Testing%20NTR%2003.pdf<br /><br />ANother advantage of nuclear over electric propulsion is efficiency. Electric propulsion uses electricity to heat fluid to evaporation or ionization temperatures at various pressures. As such, they are limited by Carnot cycle efficiencies to 20% conversion, while nuclear, as its emission is already heat, is not limited by the Carnot cycle and is therefore several times more efficient than electricity for propulsion purposes (for the same reason that passive solar power is always several times more efficient than photovoltaic).

 

[scottb50]

I don't didpute that Nuclear power can produce more than abundant amounts of heat and that by using a fluid to keep the Nuclear reactor from melting is simply an extension of the way reactors are cooled today.<br /><br />The problem I see is the amount of cooling required and the coolant needed and the continuing need to reject heat building up to operating temperatures and shutting down the reactor. If the idea is to use the reactor for boosting then discarded it I can see it working, but the cost would be pretty high. If it is to be re-usable IO see major problems in rejecting the heat generated even at reduced outputs. As an example look at the area of the radiators required to dump the heat generated inside the Shuttle from the crew and electronics.<br /><br />My point is while the reactor is operating directing coolant through the reactor would definitely cool it, but how do you control it after or before that? <div class="Discussion_UserSignature"> </div>

 

[rocketman5000]

What would the ionized oxygen do to the reactor core? I know that pure oxygen can be nasty to many components in elemental form; being such a great oxidizer and all.

 

[chew_on_this]

I recall a propulsion method which uses a large block of ice in a rocket with a ground based laser fired into the nozzle which vaporized the ice/water and using this as the propellant. Interesting concept. Much safer than volatiles.

 

[chriscdc]

I like that entry about the moon ice. You could build a space craft that could refuel quite easily on europa. Or it could form the propulsion and the drilling sections of a mission to seewhat is under europas ice.

 

[scottb50]

Ion engines are great if you have the time. I'm not sure ground based laser is really needed, most ion/ electric engines have figured out a simpler way to do it. <div class="Discussion_UserSignature"> </div>

 

[josh_simonson]

Most rockets are steam powered. The H2 and O2 burn to make pressurized steam that accelerates out the nozzle, and they're much more straightforward since the energy is held in the reaction mass, not a separate system.

 

[hyper_fule]

The advantage of the ground based laser is that you don't need to lug around the mass of a power plant. It might be better to use microwaves rather than lasers though.<br /><br />Thermal propulsion may not be as efficient as ion propulsion but it is still good design. It is probably a lot cheaper to implement than ion technology. The solar thermal design especially will probably be all over the inner planets this century. The limits of these design are in the melting point of the power plant and the volitility of propellent at high temperatures. One advantage about this design is that there isn't a lot of limit to what you can use as propellan.<br /><br />This website talks about the nuclear thermal design<br />http://www.projectrho.com/rocket/rocket3c2.html#ntrsolid<br />and some other stuff as well.

 

[mlorrey]

<blockquote><font class="small">In reply to:</font><hr /><p><br />My point is while the reactor is operating directing coolant through the reactor would definitely cool it, but how do you control it after or before that? <br /><p><hr /></p></p></blockquote><br />Okay, this is a systems engineering question, regarding the fuel flow control, when the fuel is also the coolant, versus the need to amp down the reaction rate once you are out of boost phase and into orbital insertion. AFAIKR, nuclear launcher proposals I've seen take about twice as long to get into orbit due to lower t/w ratios. I recall reading that the control system of nuclear reactors on fast attack submarines roughly fit the performance profile of a nuclear launch vehicle. <br /><br />Yes, you are creating a LOT of heat to start with, which you are carrying out as propellant after you use it as coolant. As you ascend and your vehicle mass drops and acceleration increases, you start creeping your control rods or whatever regulation mechanism you have for the reactor in to gradually draw down the reaction rate over 20 minutes or so that it takes to get into orbit. By the time you are in orbit, your reactor is just puttering along, all cooled down, and you are using hardly any coolant for propulsion, you are directing it into thermocouple and turbine generators for ship power and HVAC....