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Using these resources to improve chemical flamethrowers is sub-optimal. A dead end. Nuclear fusion is a more likely answer to spaceflight and Earth's clean en

Using these resources to improve chemical flamethrowers is sub-optimal. A dead end. Nuclear fusion is a more likely answer to spaceflight and Earth's clean energy problem. It likely should be the priority.

perl4ever 5y ago
>Nuclear fusion is a more likely answer to spaceflight and Earth's clean energy problem. Considering we don't even have fission rockets or airplanes in normal use, making a fusion powerplant that is light enough to get off the ground seems very far fetched. Even if we eventually use fusion for travel beyond earth orbit, I'd bet chemical rockets would still be in use. Don't we already have thrusters that are useful in space, but completely unable to support themselves against 1G and so they can't lift off from the ground? I feel like I've read something that said fusion power would fall in the same category.
- dmoy 5y ago
  > Don't we already have thrusters that are useful in space, but completely unable to support themselves against 1G and so they can't lift off from the ground? Yes. For example ion thrusters have specific impulse that is like an order of magnitude or two (or three?) better than chemical rockets, but they can't lift anything out of the atmosphere. > I feel like I've read something that said fusion power would fall in the same category. Sorry I have no idea about that.
- barbacoa 5y ago
  For those interested: As absurd as it sounds nuclear powered aircraft engines are a thing.[1] They have also been proposed for spacecraft, Scott Manley does a great video talking about nuclear rocket engines[2]. [1]https://en.wikipedia.org/wiki/Project_Pluto https://en.wikipedia.org/wiki/Project_Pluto [2]https://www.youtube.com/watch?v=cvZjhWE-3zM https://www.youtube.com/watch?v=cvZjhWE-3zM
  - vimacs2 5y ago
    I flirted with the idea of using supersized nuclear powered aircraft as the terrestrial version of the Aldrin cycler[1] concept. Basically, these things would be designed to never land but instead run in circular paths between continents with a fleet of onboard craft and hangers that will exchange cargo and passengers instead. They will be designed from the ground up to be maintanable and refuelable under constant operation (not a particularly difficult goal for a nuclear powered craft). Safety is a very valid concern for any supersized airborne vehicle but especially a nuclear powered one! However, this is one department where scale in itself brings it's own benefits. The volume increases faster than the surface area so you could have a hull far thicker than that of many naval ships while still having a truly vast interior volume. Not needing to ever land also reduces avenues for sabatoge and presumably the craft's interior itself would be heavily compartmentalized. You can also optimise your hull to deal with a narrow air pressure range which you cannot do with normal craft which need to be able to handle a wide range from ground level to the stratospheric. https://en.wikipedia.org/wiki/Mars_cycler https://en.wikipedia.org/wiki/Mars_cycler
  - deleted 5y ago
    [deleted]
- mr_toad 5y ago
  DFDs seem promising, but are far from producing 1G of thrust. https://en.m.wikipedia.org/wiki/Direct_Fusion_Drive https://en.m.wikipedia.org/wiki/Direct_Fusion_Drive
vimacs2 5y ago
Even if we pretended that it's rational to hedge all your bets on not only having a working fusion reacter in the near term future but having the capability to miniturise it to a degree where it could be used as an engine for a launch vehicle, you would still be dead wrong. Fusion still shares the same fundumental problem that chemical rockets or even more advanced options like blackhole or antimatter drives face - the rocket equation. We need to use near term reusable launch vehicles like the Starship to help set up the required launch assist structures that would make genuine mass transit of people and cargo into orbit possible. Things like skyhooks, lofstroom loops, and eventually orbital rings that would allow people to ride trains or cable cars from an earth city straight into orbit for the same price range as intercity travel today. Needless to say, that is not going to happen until there is enough of an industry up there to justify the large upfront costs of such megaprojects (especially the orbital ring) so the Starship is our best near term hope of getting us up to that point. Note that none of these projects require advanced materials or new technologies (as opposed to the space elevator that is likely to remain science fiction when it comes to dealing with a body with the gravity well of earth anyway), they're just massive engineering projects.
- dchichkov 5y ago
  The difference between chemical/fission and fusion are orders of magnitude. It is <10km/s for chemical/fission. And 1000km/s for fusion: "Today’s best chemical rockets produce propellant exhaust velocities up to 4.5 km/s. Fission (nuclear thermal) rocket engines could roughly double that, to about 8.5 km/s. A working nuclear fusion core producing thrust through direct exhaust of hot plasma, could readily generate up to ~1000 km/s exhaust velocities" - https://link.springer.com/article/10.1007/s10894-015-0034-1 https://link.springer.com/article/10.1007/s10894-015-0034-1 Likely necessary for advanced space flight. Likely necessary to allow for "clean energy" on earth. Unlike advances to flamethrowers.
  - vimacs2 5y ago
    Having high exhaust velocities does not mean you will have the high thrusts required to get yourself out of the earth's atmosphere. Most current proposals for Nuclear Fusion powered ships involve an exhaust that is orders of magnitude more diffuse than that of chemical rockets. They only come into their own once they are already in space or in orbit which returns us to the problem that we need to have launch assist infrastructure that can deal with that first step without resorting to those "flamethrowers" as you call them. It's also not true at all that fusion is necessary to allow for clean energy (even ignoring that many of the near term fusion reactor designs still need to have radiation shielding to deal with dangerous neutron emissions). We could use a combination of renewable sources and nuclear fission to deal with the energy crisis now and then utilise fusion once it's finally matured to the point of usefulness. Indeed, we could use that orbital infrastructure to help construct a planetary cloud of solar collectors that can operate 24/7 and beam that energy down via microwave rectiner technology that is already capable of achieving greater than 85% energy conversion (keep in mind that we lose far more energy simply from the diffusion of sunlight through the atmosphere). This approach not only can power the earth but any off earth colonisation prospects with line of sight with our planetary cloud - without needing to haul the likely massive early generation fusion reactors. Neither is fusion necessary for advanced space travel. It would be very useful but chiefly for travel to under-developed sectors of the solar system. solar reflectors scaled up enough can be used to speed up and slow down entire fleets of ships with far higher potential top speeds than even antimatter drives permit (since there is no requirement to have onboard propellant). They also double as handy point defense systems for dealing with both debris and ships that are attempting to turn themselves into relativistic kill missiles - remember that there is no such thing as an unarmed space ship, they are all potential weapons of mass destruction, especially once we reach the state where we have fusion drive powered ones.
trhway 5y ago
nuclear engines, even just the fission, are the future for the space. The thing is you'd never be able to launch them on Earth. So, the first thing is to get enough stuff into space and establish an assembly/test platform there, Moon probably. With Starship the Moon becomes just a 3 day trip for 100ton cargo while burning less than $10M of fuel. >Using these resources to improve chemical flamethrowers is sub-optimal. A dead end. Earth launch future is large rail gun (somewhere like Bolivia) as a first stage booster. Requires a bit of political will, international cooperation and a few billions. Unfortunately the 1st and 2nd aren't coming soon, so the "chemical flamethrowers" for now.

perl4ever 5y ago

>Nuclear fusion is a more likely answer to spaceflight and Earth's clean energy problem. Considering we don't even have fission rockets or airplanes in normal use, making a fusion powerplant that is light enough to get off the ground seems very far fetched. Even if we eventually use fusion for travel beyond earth orbit, I'd bet chemical rockets would still be in use. Don't we already have thrusters that are useful in space, but completely unable to support themselves against 1G and so they can't lift off from the ground? I feel like I've read something that said fusion power would fall in the same category.

dmoy 5y ago
> Don't we already have thrusters that are useful in space, but completely unable to support themselves against 1G and so they can't lift off from the ground? Yes. For example ion thrusters have specific impulse that is like an order of magnitude or two (or three?) better than chemical rockets, but they can't lift anything out of the atmosphere. > I feel like I've read something that said fusion power would fall in the same category. Sorry I have no idea about that.
barbacoa 5y ago
For those interested: As absurd as it sounds nuclear powered aircraft engines are a thing.[1] They have also been proposed for spacecraft, Scott Manley does a great video talking about nuclear rocket engines[2]. [1]https://en.wikipedia.org/wiki/Project_Pluto https://en.wikipedia.org/wiki/Project_Pluto [2]https://www.youtube.com/watch?v=cvZjhWE-3zM https://www.youtube.com/watch?v=cvZjhWE-3zM
- vimacs2 5y ago
  I flirted with the idea of using supersized nuclear powered aircraft as the terrestrial version of the Aldrin cycler[1] concept. Basically, these things would be designed to never land but instead run in circular paths between continents with a fleet of onboard craft and hangers that will exchange cargo and passengers instead. They will be designed from the ground up to be maintanable and refuelable under constant operation (not a particularly difficult goal for a nuclear powered craft). Safety is a very valid concern for any supersized airborne vehicle but especially a nuclear powered one! However, this is one department where scale in itself brings it's own benefits. The volume increases faster than the surface area so you could have a hull far thicker than that of many naval ships while still having a truly vast interior volume. Not needing to ever land also reduces avenues for sabatoge and presumably the craft's interior itself would be heavily compartmentalized. You can also optimise your hull to deal with a narrow air pressure range which you cannot do with normal craft which need to be able to handle a wide range from ground level to the stratospheric. https://en.wikipedia.org/wiki/Mars_cycler https://en.wikipedia.org/wiki/Mars_cycler
- deleted 5y ago
  [deleted]
mr_toad 5y ago
DFDs seem promising, but are far from producing 1G of thrust. https://en.m.wikipedia.org/wiki/Direct_Fusion_Drive https://en.m.wikipedia.org/wiki/Direct_Fusion_Drive

vimacs2 5y ago

Even if we pretended that it's rational to hedge all your bets on not only having a working fusion reacter in the near term future but having the capability to miniturise it to a degree where it could be used as an engine for a launch vehicle, you would still be dead wrong. Fusion still shares the same fundumental problem that chemical rockets or even more advanced options like blackhole or antimatter drives face - the rocket equation. We need to use near term reusable launch vehicles like the Starship to help set up the required launch assist structures that would make genuine mass transit of people and cargo into orbit possible. Things like skyhooks, lofstroom loops, and eventually orbital rings that would allow people to ride trains or cable cars from an earth city straight into orbit for the same price range as intercity travel today. Needless to say, that is not going to happen until there is enough of an industry up there to justify the large upfront costs of such megaprojects (especially the orbital ring) so the Starship is our best near term hope of getting us up to that point. Note that none of these projects require advanced materials or new technologies (as opposed to the space elevator that is likely to remain science fiction when it comes to dealing with a body with the gravity well of earth anyway), they're just massive engineering projects.

dchichkov 5y ago
The difference between chemical/fission and fusion are orders of magnitude. It is <10km/s for chemical/fission. And 1000km/s for fusion: "Today’s best chemical rockets produce propellant exhaust velocities up to 4.5 km/s. Fission (nuclear thermal) rocket engines could roughly double that, to about 8.5 km/s. A working nuclear fusion core producing thrust through direct exhaust of hot plasma, could readily generate up to ~1000 km/s exhaust velocities" - https://link.springer.com/article/10.1007/s10894-015-0034-1 https://link.springer.com/article/10.1007/s10894-015-0034-1 Likely necessary for advanced space flight. Likely necessary to allow for "clean energy" on earth. Unlike advances to flamethrowers.
- vimacs2 5y ago
  Having high exhaust velocities does not mean you will have the high thrusts required to get yourself out of the earth's atmosphere. Most current proposals for Nuclear Fusion powered ships involve an exhaust that is orders of magnitude more diffuse than that of chemical rockets. They only come into their own once they are already in space or in orbit which returns us to the problem that we need to have launch assist infrastructure that can deal with that first step without resorting to those "flamethrowers" as you call them. It's also not true at all that fusion is necessary to allow for clean energy (even ignoring that many of the near term fusion reactor designs still need to have radiation shielding to deal with dangerous neutron emissions). We could use a combination of renewable sources and nuclear fission to deal with the energy crisis now and then utilise fusion once it's finally matured to the point of usefulness. Indeed, we could use that orbital infrastructure to help construct a planetary cloud of solar collectors that can operate 24/7 and beam that energy down via microwave rectiner technology that is already capable of achieving greater than 85% energy conversion (keep in mind that we lose far more energy simply from the diffusion of sunlight through the atmosphere). This approach not only can power the earth but any off earth colonisation prospects with line of sight with our planetary cloud - without needing to haul the likely massive early generation fusion reactors. Neither is fusion necessary for advanced space travel. It would be very useful but chiefly for travel to under-developed sectors of the solar system. solar reflectors scaled up enough can be used to speed up and slow down entire fleets of ships with far higher potential top speeds than even antimatter drives permit (since there is no requirement to have onboard propellant). They also double as handy point defense systems for dealing with both debris and ships that are attempting to turn themselves into relativistic kill missiles - remember that there is no such thing as an unarmed space ship, they are all potential weapons of mass destruction, especially once we reach the state where we have fusion drive powered ones.

trhway 5y ago

nuclear engines, even just the fission, are the future for the space. The thing is you'd never be able to launch them on Earth. So, the first thing is to get enough stuff into space and establish an assembly/test platform there, Moon probably. With Starship the Moon becomes just a 3 day trip for 100ton cargo while burning less than $10M of fuel. >Using these resources to improve chemical flamethrowers is sub-optimal. A dead end. Earth launch future is large rail gun (somewhere like Bolivia) as a first stage booster. Requires a bit of political will, international cooperation and a few billions. Unfortunately the 1st and 2nd aren't coming soon, so the "chemical flamethrowers" for now.