4 ms·
One of the interesting things in that Wikipedia link is that you only need to run your Orion for 36 days to get it up to speed. Beyond that, detonating more bo
by jasonkester 14y ago
One of the interesting things in that Wikipedia link is that you only need to run your Orion for 36 days to get it up to speed. Beyond that, detonating more bombs won't accelerate you any further.
So yes, you could turn it around. But surprisingly it seems you can wait until a month before arrival to do so. The downside, however, is that your max velocity gets cut in half if you bring enough bombs to slow down.
With better explosives, you could get a higher max velocity and therefore closer to the "accelerate halfway, decelerate halfway" ideal case, but at the moment such explosives don't exist.
- rdl 14y agoI'm not sure how that works out. Do 36 days of acceleration at the beginning (or spread it over a year to reduce peak acceleration) -- go from 0 to 0.1c or whatever the cruise speed is. Coast for ~100 years. Spend the last year going from 0.1c to 0. It does mean you have to carry twice as many bombs, and carry half of the bombs for 149 years, but bombs are really lightweight relative to the ship. It also means you can't just jettison the pusher plate, which is probably a bigger deal.
- randallsquared 14y agoIn this case, the weight of the bombs is larger than the rest of the ship: 50K tons for the ship structure, 300K for the weight of the bombs [1]. Twice as many bombs essentially doubles launch mass. Orion is a great concept for tooling around the solar system easily, but what it buys us over interstellar distances is that it makes macroscopic payloads and reasonable travel times possible; they're still not easy. [1] Table 2 in http://galileo.phys.virginia.edu/classes/109.jvn.spring00/nuc_rocket/Dyson.pdf http://galileo.phys.virginia.edu/classes/109.jvn.spring00/nu...
- mikeash 14y agoJust to reinforce: Orion is still a rocket. And not a particularly efficient rocket, either. It uses an incredibly energy-dense fuel, but not so dense to allow you to ignore the rocket equation.
- duopixel 14y agoWhat if instead of braking Orion itself, it just drops off a lighter satellite that is able brake without expending so much energy?
- Tichy 14y agoI'd think it would still have to brake using Orion technology, so it is doubtful if it could be built smaller than Orian itself.
- JoeAltmaier 14y agoIt could use solar wind, or gravity-slingshot (which can slow as well as accelerate a satellite). So yes it could be much smaller.
- rdl 14y agoI wonder if Elon Musk has ever spoken about Orion. I'd love to live in a world in 2030 or so where a private shuttle runs Earth-Mars every few weeks using Orion technology, since it wouldn't then need to operate on energy-conserving orbits.
- fhars 14y agoIt's not twice as many bombs, it is (using your numbers) six time as much bomb mass as payload mass, so 50Kt payload, 300Kt bombs for slowing down, which gives you 350Kt payload for the acceleration phase, which would require another 2100Kt of bombs to get up to speed, for effectivley seven times the launch mass