## Search found 102 matches

Sun Nov 15, 2009 12:28 pm
Forum: Implications
Topic: Rocket thrust
Replies: 98
Views: 49926
According to atomic rocket , the dose limits are: general public: 0.04Rem, 5Rem (0.5 for minors) occupational: 0.4Rem, 5Rem, ~200Rem astronaut: 150Rem, 300Rem, 400Rem That's 30day limit, Yearly limit, Career Limit. Also, I did the conversions from Sieverts to Rems in my head, so there may be mistakes.
Sun Nov 15, 2009 12:20 pm
Forum: General
Topic: Gone to the moon, BRB(Destination Moon)
Replies: 12
Views: 6370
Heh :) Anyway, I figured out why djolds1 was saying my math wasn't enough to account for gravity drag: it's because it takes time to build up that delta-v. I'm running a simulation of a ship going from LEO (150km) to "lunar" orbit (ie, same orbit as the moon, not in orbit around the moon). I set the...
Sun Nov 15, 2009 6:11 am
Forum: Implications
Topic: Rocket thrust
Replies: 98
Views: 49926
What about the X-rays and Gamma rays? They're the real problem. I don't know about X-rays, but Gamma rays are expected to be about 0.1% of output power, so you need to factor in 6MW of gamma radiation.
Sun Nov 15, 2009 6:07 am
Forum: General
Topic: Gone to the moon, BRB(Destination Moon)
Replies: 12
Views: 6370
Oh, indeed, but Isp isn't even half the equation. For any specific Isp, you can get from LEO to the Moon so long as you have enough reaction mass. (reaction_mass+dry_mass)/dry_mass = exp (delta_V/(g*Isp)) Of course, it gets ugly fast as your Isp drops. And then the power requirements are proportiona...
Sun Nov 15, 2009 4:12 am
Forum: General
Topic: Gone to the moon, BRB(Destination Moon)
Replies: 12
Views: 6370
I don't know about ISP (I don't grok it yet), Isp is best thought of as the measure of rocket efficiency. Technically it is the velocity of the rocket exhaust products divided by gravitational acceleration. For example, H2/LOX has an exhaust velocity of ~4500m/s, and a theoretical max Isp of just o...
Sat Nov 14, 2009 6:08 am
Forum: General
Topic: Gone to the moon, BRB(Destination Moon)
Replies: 12
Views: 6370
I don't know about ISP (I don't grok it yet), but the other day I worked out that you need at least about 12km/s delta V to get to lunar orbit (ie, to get into a similar orbit to the moon, not orbit around the moon (eg, leading/trailing trojan): that will be a little extra). Orbital velocity in LEO ...
Sun Nov 08, 2009 6:57 am
Forum: Implications
Topic: Rocket thrust
Replies: 98
Views: 49926
93143: Oops, so it is. "F=Me*Ve" is such a fundamental equation to the derivation of the rocket equation, I got the two confused.
Thu Nov 05, 2009 10:02 am
Forum: Implications
Topic: Rocket thrust
Replies: 98
Views: 49926
Start from first principles... Basic rocket equation: F=Me*Ve F = thrust in Newtons Me = propellant mass rat (kg/s) Ve = velocit of propellant (m/s) E=M*V^2/2 (energy) (^ is power) P=E/t (power) Using dimensional analysis (sorry, don't know of a better way to show this): E=kg*(m/s)^2/2 (I think cons...
Tue Nov 03, 2009 3:45 am
Forum: Design
Topic: Some sci-fi questions
Replies: 35
Views: 13689
Ah, nice. I was wondering where the neutrons and gamma rays would come from. Even better, I've got some numbers to work with. However, one important thing I noticed: that article is for thermal plasmas (tokamak etc?). I imagine a polywell would be quite different (though how is another matter). That...
Mon Nov 02, 2009 2:10 pm
Forum: Design
Topic: Some sci-fi questions
Replies: 35
Views: 13689
It's not the shielding of the gamma rays that bothers me (as you said, just add (appropriate) mass), but rather the waste (Carnot efficiency, radiator mass, etc). p+15N being aneutronic, producing reasonable energy, and having the shortest "time" (and thus highest probability) is what made me agree....
Mon Nov 02, 2009 8:36 am
Forum: News
Topic: Rick Has A Word or two for sceptics.
Replies: 128
Views: 31546
There's alot to be said for the perseverance that motivates a man to pick up the torch from where his predecessor has failed and carry on, its the spirit that gave us the industrial revolution. I'd be inclined to say it's the spirit that gave us the stone axe, are maybe even that blade of grass stu...
Mon Nov 02, 2009 12:36 am
Forum: Design
Topic: Some sci-fi questions
Replies: 35
Views: 13689
Hello, I'm new here (though I've been reading for the last month or so). I'm a complete layman*, so anything I say is most likely to be swiss cheese. I too am interested in the polywell for scifi (and for real, too). Anyway, regarding information on the CNO cycle, there's wikipedia (though I imagine...