So I've read ideas on building an "atomic verne cannon", but a big problem was the fact that one would need to dig a new launch tube/barrel after every shot. You would also need to somehow build or dig out a huge chamber to fill with water.
Quote from: nmurali on 07/06/2018 07:14 pmSo I've read ideas on building an "atomic verne cannon", but a big problem was the fact that one would need to dig a new launch tube/barrel after every shot. You would also need to somehow build or dig out a huge chamber to fill with water. The latter informs the solution to the former. You hang a disposable tube underwater at the desired launch angle. Set off the nuke at one end. Water is incompressible (beyond a certain distance from the detonation), so if the tube is filled with gas instead of water, it is the only compressible path for the nuclear overpressure to escape.
Quote from: Paul451 on 07/23/2018 10:00 pmQuote from: nmurali on 07/06/2018 07:14 pmSo I've read ideas on building an "atomic verne cannon", but a big problem was the fact that one would need to dig a new launch tube/barrel after every shot. You would also need to somehow build or dig out a huge chamber to fill with water. The latter informs the solution to the former. You hang a disposable tube underwater at the desired launch angle. Set off the nuke at one end. Water is incompressible (beyond a certain distance from the detonation), so if the tube is filled with gas instead of water, it is the only compressible path for the nuclear overpressure to escape. ..assuming no marine life (with compressible internal organs) happen by.Man, the greenies would have a field day with this idea.
Quote from: CameronD on 07/24/2018 03:30 am..assuming no marine life (with compressible internal organs) happen by.Man, the greenies would have a field day with this idea. They'd be about 40 years too late for that party.
..assuming no marine life (with compressible internal organs) happen by.Man, the greenies would have a field day with this idea.
Quote from: Paul451 on 07/23/2018 10:00 pmThe latter informs the solution to the former. You hang a disposable tube underwater at the desired launch angle. Set off the nuke at one end. Water is incompressible (beyond a certain distance from the detonation), so if the tube is filled with gas instead of water, it is the only compressible path for the nuclear overpressure to escape.When you add up the costs of the nuke, the disposable tube, the disposable ablative covering to get the payload through the atmosphere, and whatever mechanism you are going to use to circularize the orbit so it doesn't re-enter the atmosphere, I believe this launch system is going to be more expensive per pound of payload than BFR/BFS.
The latter informs the solution to the former. You hang a disposable tube underwater at the desired launch angle. Set off the nuke at one end. Water is incompressible (beyond a certain distance from the detonation), so if the tube is filled with gas instead of water, it is the only compressible path for the nuclear overpressure to escape.
Nukes are pretty cheap on a dollar per GJ basis. Tsar bomba 210PJ about 200 million GJ, which in natural gas terms is worth about $0.5-1billion. CH4-LOX rocket fuel of same total energy is about $1-2billion. thermo nuclear bombs only cost on the order of $10million each so have an energy cost as little as 1% of rocket fuel. Hydrogen bombs can be pretty clean too - <3% fission for tsar bombaIf you could get sufficient energy-coupling into the projectile and if you were only interested in launching oversized man-hole covers (Pascal-B nuke test 900kg manhole cover capping a 150m deep shaft estimated speed of 66km/s ) it might be worth it. Getting a large amount of steel or aluminium or other metals in orbit or to Mars or moon cheaply to build with might have great value.[Edit] Also a very cheap way to launch a lot of mass from the Moon or Mars for orbital construction.
Quote from: ChrisWilson68 on 09/17/2018 04:59 pmQuote from: Paul451 on 07/23/2018 10:00 pmThe latter informs the solution to the former. You hang a disposable tube underwater at the desired launch angle. Set off the nuke at one end. Water is incompressible (beyond a certain distance from the detonation), so if the tube is filled with gas instead of water, it is the only compressible path for the nuclear overpressure to escape.When you add up the costs of the nuke, the disposable tube, the disposable ablative covering to get the payload through the atmosphere, and whatever mechanism you are going to use to circularize the orbit so it doesn't re-enter the atmosphere, I believe this launch system is going to be more expensive per pound of payload than BFR/BFS.Nukes are pretty cheap on a dollar per GJ basis. Tsar bomba 210PJ about 200 million GJ, which in natural gas terms is worth about $0.5-1billion. CH4-LOX rocket fuel of same total energy is about $1-2billion. thermo nuclear bombs only cost on the order of $10million each so have an energy cost as little as 1% of rocket fuel.
Nukes are pretty cheap on a dollar per GJ basis. Tsar bomba 210PJ about 200 million GJ, which in natural gas terms is worth about $0.5-1billion. CH4-LOX rocket fuel of same total energy is about $1-2billion. thermo nuclear bombs only cost on the order of $10million each so have an energy cost as little as 1% of rocket fuel. Hydrogen bombs can be pretty clean too - <3% fission for tsar bomba
If you have to manufacture new devices
but if you want to industrialize space, you ultimately need raw materials.
I never responded to this part in the OP:Quote from: nmurali on 07/06/2018 07:14 pmbut if you want to industrialize space, you ultimately need raw materials.Do you? Is bulk material that significant? I mean given where we are technologically.If a 100,000 tonne nickel-iron asteroid somehow lunar-slingshotted and atmospheric-skipped and chaosed its way into an ~800km Earth orbit, would the space programs of the world change that drastically? You'd still need cheap launch, manned spaceflight, space-rated robotic systems, etc etc. Sure, everyone has a new-shiny to play with for awhile, but how much really changes? (Obviously the asteroid-mining crowd would lose their collective. And there might be some strategic games between nations trying to claim it without breaching OST. But that's not the analogy, it's about the effect of having material up there.)
But with SpaceX having a marginal cost of launch close to $1000/kg now they could launch 10000 tonnes for about $10 Billion. So orion propelled asteroid or moon rock exploitation is less necessary for LEO development.
We have banned nuclear testing in Earth's atmosphere. So you may be able to use a nuclear cannon on the Moon and possibly Mars but that is it.
Quote from: RobLynn on 09/18/2018 01:02 amNukes are pretty cheap on a dollar per GJ basis. Tsar bomba 210PJ about 200 million GJ, which in natural gas terms is worth about $0.5-1billion. CH4-LOX rocket fuel of same total energy is about $1-2billion. thermo nuclear bombs only cost on the order of $10million each so have an energy cost as little as 1% of rocket fuel. Hydrogen bombs can be pretty clean too - <3% fission for tsar bombaThis is a spectacularly bad comparison. Even in the fantasy land of atomic space gun launch, you aren't going to be using Tsar Bomba size devices*, you are going to be using the opposite end of the spectrum. Small devices have significantly less favorable cost and pollution characteristics.The assertion that nukes are cheap also depends on which costs you choose to include. The incremental cost of another unit may indeed be in the tens of millions range, but the nuclear complex as a whole is mindbogglingly expensive. If you have to manufacture new devices with in a way that doesn't result in Hanford style messes, the unit costs are going to be significantly higher. From BOTE, the Hanford cleanup related costs of US weapons alone exceeds $2 million each.* The neighbors would complain, and by neighbors I mean neighboring continents.