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View Full Version : Can Whipple shields be scaled up?



JohnBStone
2008-Mar-09, 03:34 PM
I understand that Whipple shields can effectively dissipate the kinetic energy of hypervelocity micrometeorites. Can they practically be scaled up against larger and/or denser objects? (assuming we could launch the craft in the first place)

Could we build one that dissipated an iron 1 kg object, 10kg, 100kg? at 10kps.

Does a large or dense object vaporize fast enough to not go through the shield?

(A web search only reveals Whipple shields against small particles)

antoniseb
2008-Mar-09, 04:10 PM
Could we build one that dissipated an iron 1 kg object, 10kg, 100kg? at 10kps.

Sure, it can be scaled up, but it might not seem practical.
Suppose you are looking at building one for a large installation on the Moon, and you decide that you need to protect against 100kgs at 20kps (allowing for some added infall velocity). You could reasonably have several layers of battleship plating forming a dome over the facility, but it might be a lot cheaper to just build the facility at the bottom of a modest sized crater and bury it under a hundred meters of lunar debris.

mugaliens
2008-Mar-12, 08:42 PM
I understand that Whipple shields can effectively dissipate the kinetic energy of hypervelocity micrometeorites. Can they practically be scaled up against larger and/or denser objects? (assuming we could launch the craft in the first place)

Could we build one that dissipated an iron 1 kg object, 10kg, 100kg? at 10kps.

Does a large or dense object vaporize fast enough to not go through the shield?

(A web search only reveals Whipple shields against small particles)

Well, anything with a large enough magnetic capability can be shielded against.

The problem is that there are many elements that are plentiful in outer space can't be shielded against because of their chemical nature.

It's really not rocket science. It's just that the physical characteristics don't allow it.

Sure, we can send things through low light speeds with physical shielding, but at high light speeds and much longer distances, we'd need something with a bit more like Star Trek's Deflector Shield, and to date, we really don't know what the physics of this technology would require. (well, we have an idea, but we're just not there yet, and perhaps the physics will never be available to us). I really do think we're trying, but I don't know if the breakthrough is going to happen 20 years from now, 50,000 years from now, or never (technologically impossible).

Ok?

IsaacKuo
2008-Mar-13, 03:01 AM
Whipple shields have absolutely nothing to do with magnetic fields. They are physical shields made of thin layers spaced apart from each other. As antoniseb noted, they can be scaled up to larger impactors; whether it makes sense to do so depends on the specifics of the mission.

As for protection at relativistic speeds, a simple magnetic field along with a thin ionizing foil/foam/mesh/gas shield could provide Star Trek Deflector shield levels of performance, but doesn't require Star Trek magic tech/science.

At 95% of the speed of light, a firmly non-magical 10Tesla magnetic field will deflect fully ionized nuclei within about three meters. So all you need is a very low mass foil or foam or mesh or gas shield at least three meters in front of the starship to fully ionize the incoming (at 95% of c, it takes hardly any mass to fully ionize an incoming impactor). The best ionizing shield may actually be a thin "bubble" of plasma around the torus shaped starship. Interstellar medium and dust impacting the plasma field actually replenishes the plasma field. It's like a roach motel for atoms. An uncharged neutral atom cruises straight through the magnetic field until it slams into an electron or nucleus. This ionizes the atom and the resulting ion and electrons are then trapped spiraling around the magnetic field lines.

mugaliens
2008-Mar-15, 05:07 PM
Well, if they're physical shields, then given enough mass, any level of shielding is theoretically possible given enough reaction mass, thrust, etc., and all the other elements of rocketry.

I would think, though, given our current level of technology, that we'd have solved this via some other means.

IsaacKuo's idea sounds good. Here's another - spit the remaining mass out as physical barrier.

IsaacKuo
2008-Mar-17, 02:33 PM
Well, if they're physical shields,

Whipple shields ARE physical shields. There is no "if" about it.

A Whipple shield is a sort of spaced armor, made of several thin layers spaced apart from each other rather than a single thick layer. At the impact velocities it is designed for (ten km/s to tens of km/s), this is more effective than a single thick layer.

BigDon
2008-Mar-18, 05:07 PM
Whipple shields ARE physical shields. There is no "if" about it.

A Whipple shield is a sort of spaced armor, made of several thin layers spaced apart from each other rather than a single thick layer. At the impact velocities it is designed for (ten km/s to tens of km/s), this is more effective than a single thick layer.

Mr. Kuo is correct, and this is an old concept.

Near where I live we have Fort Funston, designed to withstand an onslaught from large WWII-era naval guns, (1227 kilo projectiles moving at 820 meters per second) is built using this premise. Alternating layers of foot thick armor plate, several feet of sand as a "burster course" and layers of re-enforced concrete. And not just one layer of each. (And she could give as good as she could take. With 16 inch guns of her own, and not being able to "sink".)

neilzero
2008-Mar-19, 01:07 AM
Hi IsaacKuo, post #4: We have not tested nanogram projectals at 0.95 c, so they may not be mostly ionized a kilometer after passing though several whipple shields. Picogram perhaps? Reversing the direction of a 10 nanogram iron ball in three meters = ten? nanoseconds also seems improbable, with less than 1000 tesla. Have you a link or explanation? Neil

IsaacKuo
2008-Mar-19, 09:59 AM
Hi IsaacKuo, post #4: We have not tested nanogram projectals at 0.95 c, so they may not be mostly ionized a kilometer after passing though several whipple shields. Picogram perhaps?

I'm not suggesting the use of Whipple shields to defend against relativistic projectiles. Whipple shields were designed with orbital and interplanetary debris in mind, and they're appropriate for that domain. The sort of defense I described would be more appropriate than Whipple shields for relativistic particles.

We do not have to accelerate a nanogram projectile to 0.95c in order to figure out what happens when a nanogram projectile hits particles at 0.95c. The heavy "projectile" can be a sitting target, which is hit by a 0.95c particle beam--these speeds ARE achieved by particle beams, and while the mass of the particle beam isn't very much it is concentrated onto a very narrow impact area. It doesn't take much impact energy to fully ionize what's hit. Not compared to the specific energy of a 0.95c beam--it's orders of magnitude different.


Reversing the direction of a 10 nanogram iron ball in three meters = ten? nanoseconds also seems improbable, with less than 1000 tesla. Have you a link or explanation? Neil

The relevant force involved is the Lorentz force: http://en.wikipedia.org/wiki/Lorentz_force

The radius of curvature depends only on the charge/mass ratio and the velocity. One reason why the radius of curvature may be much smaller than you'd expect is that the magnitude of the force increases in proportion to the velocity of the particle. The faster the particle, the greater the force it experiences. The radius of curvature still goes up with increasing speed, but not as much as you might expect.