Quote from: hop on 08/21/2017 05:40 pmQuote from: puttelino on 08/21/2017 09:20 amOn top of the impactor we put a smaller version of the proposed Orion damper with a large nuke behind it. The impactor now has a high delta-V. Just Before impact, we detonate the nuke and give the impactor at huge boost in speed. Plus any energy the nuke itself Projects around the plate.What do you gain by transferring energy from the nuke, to the impactor and then to the target? Why not cut out the middle man?In general, nukes have the highest energy density, so launching a combination of nukes + kinetic impactors gives you less capability than using the same mass of nukes alone. Kinetic impactors are technically and politically simpler, so they are attractive in cases where they provide sufficient energy in a reasonable launch mass.Yes, really should have thought about that. How ever I read only 40% of the nukes energy is radiation and what not. If we put a gas between the impactor and the nuke. Could we also harwest the pressure wave in som manner and get more energy out of it?
Quote from: puttelino on 08/21/2017 09:20 amOn top of the impactor we put a smaller version of the proposed Orion damper with a large nuke behind it. The impactor now has a high delta-V. Just Before impact, we detonate the nuke and give the impactor at huge boost in speed. Plus any energy the nuke itself Projects around the plate.What do you gain by transferring energy from the nuke, to the impactor and then to the target? Why not cut out the middle man?In general, nukes have the highest energy density, so launching a combination of nukes + kinetic impactors gives you less capability than using the same mass of nukes alone. Kinetic impactors are technically and politically simpler, so they are attractive in cases where they provide sufficient energy in a reasonable launch mass.
On top of the impactor we put a smaller version of the proposed Orion damper with a large nuke behind it. The impactor now has a high delta-V. Just Before impact, we detonate the nuke and give the impactor at huge boost in speed. Plus any energy the nuke itself Projects around the plate.
Something neat I have seen recently they want to make was a space based phased array that could superheat a point. With enough energy the rock can be vaporized and acts like a rocket via the vaporization. The object can be diverted with out much delay as the energy travels at the speed of light. I think they also suggested other uses for it such as photon propulsion for spacecraft and moving asteroids for mining, power transport. I had pondered an earth based array that used atmosphere correction similar to some telescopes.
On the other hand, in space, to my knowledge, a nuclear bomb could not cause a blast, a shock wave because of the absence of air.
Hello, when a nuclear bomb explodes on Earth it causes a blast, a shock wave that can blow and repel objects.On the other hand, in space, to my knowledge, a nuclear bomb could not cause a blast, a shock wave because of the absence of air.So how could a nuclear bomb deflect an asteroid ?Thanks !
Would the radiation pressure be sufficient?I have always had the image of radiation pressure as the very weak force pushing a solar sail.I read about the orion project and if I understood correctly they would have used a nuclear bomb where the radiation is converted into heat with a material opaque to the radiation and then this heat is directed towards a tungsten plate which vaporizes and the plasma resulting from this vaporization would have hit the thrust plate which would have created the thrust. So he wasn't using the radiation pressure to push her, not directly.I don't know if the radiation pressure alone would have been enough to create enough thrust.
So if I understand correctly a nuclear bomb without a tungsten plate which would explode near an asteroid would only produce radiation (ignoring the vaporized bomb shell) and it would produce radiation pressure on the asteroid (like light sun on a solar sail) but I imagine that this radiation pressure alone would create such weak thrust on the asteroid that it wouldn't deflect it? On the other hand, if this same bomb explodes close enough to the asteroid, the radiation from the bomb could heat the surface of the asteroid enough to cause it to vaporize and transform part of it into gas or plasma which, by escaping from the surface of the asteroid, asteroid would cause significant thrust and deflect it.
Whitelancer64 points out to me that the most common US nuke developed for missile deployment is the W87, which has a yield of 475kT (updated from 300kt - see wiki), or ~17x less than my hypothetical 8Mt nuke. However they are also lighter at ~250kg.It's hard to believe that only one would be sent at a time (they were designed to be sent 12 at a time which is easily with the capability of an F9), but if it were, one would have to adjust the numbers in my table up (can't find the original table so just doing this by hand). Again assuming 1% conversion to kinetic energy.Time to deflect asteroid by one earth diameter for 1x W87, or 12x W87:12km (Dino killer): 4930 days (13.5 years), 411 days4km: 949 days (2.59 years), 79 days1km: 117 days, 9.7 days250m: 14 days, 1.2 days
Quote from: Propylox on 07/24/2017 02:28 amQuote from: mikelepage on 07/23/2017 05:08 am... Again assuming 1% conversion to kinetic energy. Time to deflect asteroid by one earth diameter for 1x W87, or 12x W87:250m: 14 days, 1.2 days 1) Where are getting the 1% conversion assumption? Is that based on vaporization of surface material?Nothing so sophisticated. The way I thought of it is that the explosive energy radiates evenly in all directions, and you don't necessarily want to explode a rubble pile so much as shift it. You would probably perform a stand off explosion at some distance from the asteroid so the energy front from the bomb is roughly unidirectional.Surface area of a sphere is 4πr2, (or 41253 square degrees) so 1% conversion to KinE assumes that the asteroid takes up about a 20 x 20 degree patch of sky relative to the bomb. Or in other words, for a 250m asteroid, if the bomb is detonated 731m away, that means 1% of the energy from the bomb reaches the asteroid. You could go closer, but you're more likely to break it up into multiple impactors. 1% was a nice round number.Quote2) After the Chelyabinsk meteor, Russia declared a single Dnepr (RS-36) with ten warheads (550-750kt each) would obliterate a 100m object with only a few hours notice. Impacting converts the majority of energy into kinetic - as opposed to simply brushing the surface with radiation. Having "bunker buster nukes" already designed for impacting is a bonus, unless you're the target.Yeah but for anything in the 200m-1km range, you just break the asteroid into multiple impactors, which makes it way more likely that one of them hits a populated area. Even a largish tsunami from a single ocean impact (that could be prepared for/evacuated from) would spread the damage out more than multiple chaotic airburst explosions on top of a heavily populated continent.
Quote from: mikelepage on 07/23/2017 05:08 am... Again assuming 1% conversion to kinetic energy. Time to deflect asteroid by one earth diameter for 1x W87, or 12x W87:250m: 14 days, 1.2 days 1) Where are getting the 1% conversion assumption? Is that based on vaporization of surface material?
... Again assuming 1% conversion to kinetic energy. Time to deflect asteroid by one earth diameter for 1x W87, or 12x W87:250m: 14 days, 1.2 days
2) After the Chelyabinsk meteor, Russia declared a single Dnepr (RS-36) with ten warheads (550-750kt each) would obliterate a 100m object with only a few hours notice. Impacting converts the majority of energy into kinetic - as opposed to simply brushing the surface with radiation. Having "bunker buster nukes" already designed for impacting is a bonus, unless you're the target.
You have it right, but the other answer is also more or less correct. The asteroid would act as a pusher plate and be deflected by the plasma from the explosion of an Orion type shaped charge. Even though the asteroid is probably not a very good pusher plate, but it's basically action and reaction Newtonian physics.To increase the effectiveness you might want to detonate the nuclear charge close enough to the asteroid to vaporize some of the asteroids material into a gas, or even into a plasma. Depending on how effective the coupling is, and how the hole dug into the asteroid shaped itself, you would end up with a short lived but very energetic jet that would push the asteroid onto a new course.If the asteroid was not strong enough, then it might break itself into smaller bits, and some of these might still be on the original trajectory. So there probably is an art to it.
Thing is, W87 is off the shelf more or less, but what we actually want is a nuclear shape charge like a Casaba Howitzer. for high directionality.
If the asteroid is of the "rubble pile" type, and the warhead is fairly rugged, what if it is just pushed or impacted INTO the asteroid some meters. I'm thinking of the recent probe experience, where it gently sank into the rubble. Would it impart enough "thrust" through the ejecta to alter the orbit enough to avoid a collision with Earth months down the line? Or, perhaps a penetrating conventional warhead (bunker-buster), followed by a nuclear device into the hole or crater created?Fun with explosives!