tree hugging aside, is a nuclear launcher feasible?

[jurgens]

VASIMR could probablly get even more thrust in the future if they could figure out a way to get the hydrogen plasma to fuse right before exiting the nozzle.

 

[henryhallam]

<font color="yellow">Not entirely true, it's moved beyond the paper stage and has been 'bench' tested. </font><br /><br />Nice! Do you have any links to up-to-date information about this?<br />

 

[najab]

><i>...for the thruster to be useful for a human mission to Mars it needs four to six megawatts of power...</i><p>The hurdle is getting the first reactor up there. Once we do that and the public notices that the world didn't explode and the Sun still shines getting a 6 megaWatt reactor on orbit will just be a matter of logistics.</p>

 

[spacefire]

with Ion thrusters, they eject the electrons(collected from the engine) in the exhaust to neutralize it (and the engine too)<br />can they do that with plasma? also, plasma will cool upon expansion, just like any gas, so it won't be plasma anymore after it leaves the nozzle?!?!?! <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[najab]

Do a Google search on VASIMR prototype, and you should get some useful hits.

 

[jurgens]

Yeah, I don't think a 6MW reactor is the problem considering they have 200MW reactors running some Navy Submarines, of course they benefit from having a really good way to cool the reactor, Im sure they can get a 200MW reactor down to at least 6MW for space use.<br /><br />A 200MW VASIMR would be quite an engine =) Assuming the calculations are quoted correctly above, .0022m/s constant acceleration, starting from 0m/s on earth, and going to mars would only take 82 days. Now considering y ou have to travel a bit more distance because of the way orbital mechanics works and considering the fact that you already have a significant velocity to start with, a 200MW 100ton vasimr equipped spacecraft should be capable of reaching mars in less than 3 months, probablly even less then 2 months.<br /><br />It's imo, the perfect engine to run a Earth--Mars--Saturn tug. No need to refuel the reactor for years, only need to provide some hydrogen fuel to it! (I think Saturn is the better gas giant for humans to go to, as far as finding a habitat for future humans to colonize) <br /><br /><br />Also If I remember anything about VASIMR, it has variable thrust, so it can, when accelerating out of earth orbit, get a much higher thrust, and go into low thrust mode when cruising to mars/saturn.

 

[rybanis]

Saturn? <br /><br /><br />You do realize how much farther Saturn is from Mars, right? With propulsion like that, it would still take a very long time (in relation to how long it would take to get to mars) to get to Saturn. Also: why Saturn? <div class="Discussion_UserSignature"> </div>

 

[trailrider]

It isn't the opposition to polluting the Earth's environment that is completely wrong...it's the ignorant, blind and unreasoning opposition to anything "nuk-u-lar," that is the problem. In fact, these are the same people who oppose ANYTHING new and foreign to their thinking, and won't take the trouble to be educated, or close their minds to anything the slightest bit hazardous!<br /><br />These are the same people who scream bloody murder about SUV's and "gas-guzzling" automobiles, without realizing that a large proportion of our petroleum usage goes to petro-chemicals, pharmaceuticals and a lot of other stuff used in everyday life! But Heaven forbid we should disturb a carabou to lay a pipeline, or drill in the ANWR to advance out economy!<br /><br />Unfortunately, there are enough of their constituents with the same outlook who keep re-electing them, time-and-time again!<br /><br />I'm not sure we will see nuc'lar boosters taking payloads off from the Earth's surface. But if we can get to the Moon and create some research/test facilities on the backside, we might be able to produce something that will make trips to Mars more economical, both time- and energy-wise!<br /><br />Ad Luna! Ad Aries! Ad Astra!<br />Trailrider

 

[najab]

><i>...or drill in the ANWR to advance out economy...</i><p>This is really "Environment" or "Free Space" material, but... the amount of oil in ANWR will not make that much of a difference. Remember when Alaskan North Slope oil was going to make the US independent of Arabian oil for decades? It's mostly gone now. Nuclear is the only real option.</p>

 

[crix]

We're probably not getting a VASIMR though. I was just playing with some numbers for a 600kW Hall thruster-cluster with our assumed 30N thrust. Assuming a constant mass for the thruster/propellant and the cargo I used 200,000kg as my figure (Your suggestions, please). This gives us an acceleration of 0.00015m/s^2. <br /><br />1 hour - /> .54 m/s<br />1 day - /> 12.96 m/s<br />1 week - /> 90.72 m/s<br />1 month - /> 2721.6 m/s<br /><br />:-/<br /><br />Doing a super rough calculation assuming the moon is 384,000 km away and the craft is accelerating the first half and decelerating the second half, i get ~37 days from Earth to the Moon. I think this is a valid ballpark estimate. I guess these numbers aren't too much to be dissapointed about actually. If the NEP tug is just used for cargo then this would be an excellent vehicle to add to our PERMANENT SPACE EXPLORATION INFRASTRUCTURE. <img src="/images/icons/smile.gif" />

 

[spacester]

<font color="yellow">The hurdle is getting the first reactor up there.</font><br /><br />Send the first reactor up not only cold, but unfueled.<br /><br />Then, on your most reliable launcher, send a batch of fuel canisters. Send enough for around 20 reactor-years of power production. Send them to the moon or L4 – away from LEO at the least. Send your unfueled reactor to meet them and plug one of them puppies in.<br /><br />Send more reactors, meet up with fuel canisters, fire them up.<br /> <br />(edit: crix, that figure for a month is way off, everything else is OK. I get 0.777 km/s after a month with 100,000 kg = 100 tonne total mass.) <div class="Discussion_UserSignature"> </div>

 

[scottb50]

Remember when Alaskan North Slope oil was going to make the US independent of Arabian oil for decades? It's mostly gone now.....<br /><br />And most of it went to Japan anyway. <div class="Discussion_UserSignature"> </div>

 

[rybanis]

Have any of you read the book <i>Voyage</i>, by Stephen Baxter? Yes, its only fiction, but man a certain chapter (hint: Apollo-NERVA), still gives me shivers. <div class="Discussion_UserSignature"> </div>

 

[crix]

Using 100,000kg (100mT) I get that .777km/s velocity as well. My original figures are for 200mT.

 

[henryhallam]

I made a spreadsheet representing a NEP Earth-moon-Earth cargo shuttle capable of delivering 80 tonnes to lunar orbit on each trip. Each trip requires two launches of an 80-tonne payload SDV, and the vehicle itself requires one SDV launch at the beginning of the programme.<br /><br />Excel format:<br />http://henryhallam.cjb.net/~henry/NEP_to_moon.xls<br /><br />Webpage format:<br />http://henryhallam.cjb.net/~henry/NEP_to_moon.htm <br /><br />Would appreciate some feedback on the feasibility of the numbers I used.<br /><br />Edit: I think I may have made a false assumption, that SMART-1 used its ion drive continuously. Some pages say it was used only for half the time, in between periods of coasting. This won't affect the mass values or dV etc in my spreadsheet, it'll just mean that the trip time is longer.

 

[henryhallam]

I have updated the spreadsheet to allow coast time, and a few more changes.