Nuclear drives vs ion drives

[holmec]

I watch a documentry on the Science channel about how we could go to Mars. In it they disscussed a nuclear rocket based on the nuclear plane research - "phoenix" I believe. Anyway, they showed a space ship with this rocket and an enourmous amount of Hydrogen to propelle this thing. But pound for pound how does a nuclear rocket compare to an ion drive - as in Deep Space 1? And could it be possible to create an ion drive that can propell the ship to Mars at an acceptable acceleration but carrying much less gas? <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>

 

[vogon13]

Isp for nuclear thermal rockets believed to be double that of SSME fuels of H2 and O2.<br /><br />Power requirements for ion drive to yield acceleration of a plausible manned craft of 1% earth's gravity would be large. As in really, really, really large. <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>

 

[spacester]

<font color="yellow">With 200MW you could get there in 4 weeks</font><br /><br />With what size crew? What are you assuming for a specific power number (kg/kw)?<br /><br />Nuclear power is not a universal cure-all for interplanetary travel. Ignoring for the moment that the technology doesn't exist and that IMO we should not wait for FutureTech before we start getting serious about the Space Age . . . <br /><br />Generating that much power is going to take a LOT of mass. And that's before you start accounting for heat rejection and shielding.<br /><br />I've never seen a practical design concept for nuclear drive with four-weeks-to-Mars capability, even if one assumes the reactor and thrust-producing systems are ready to go. Maybe I'm not looking hard enough, but maybe there's no such thing . . . <div class="Discussion_UserSignature"> </div>

 

[najab]

><i>Generating that much power is going to take a LOT of mass.</i><p>Depends on if we're talking MW(e) or MW(t) - I agree that 400MW(e) would take a lot of mass, but 400MW thermal could be done for a few thousand pounds. (Or course, if you don't want the crew to glow when they get to Mars....)</p>

 

[shyningnight]

I agree that Nuclear is not a universal cure all..<br />And I agree that there is no nuclear-thermal "flight hardware" at this time..<br /><br />But considering that the Nerva program tested nuclear thermal engines with pretty good sucess over *40* years ago....<br />The TECHNOLOGY exists... it may not be fully mature, and it's not flyable hardware right now...<br /><br />We very much need to start dusting off the 40 year old research and build some flyable nuclear thermal hardware... <br />4 weeks is overly optomistic for the near-term, but if we can cut the 2-1/2 year trip down to 14 months, it's worth doing.<br /><br />Paul F.

 

[shyningnight]

Quite right.. good catch.<br />I posted before I'd had sufficient caffeine <img src="/images/icons/smile.gif" /><br /><br />Paul F.

 

[nacnud]

The difference is the subs are mostly 'out of sight and out of mind' and when they go wrong they sink to the sparsely populated ocean depths. However rockets occasionally fail in spectacular ways, however safe the payload really is the idea that such a failure with a nuclear payload frightens a lot of people.