Magnetic Ring Could Launch Satellites, Weapons

MattSparkes writes, "A new study funded by the US Air Force has suggested a cheaper method of sending satellites (possibly missile weapons) into orbit. A 2-km-wide ring of superconducting magnets would contain and propel a payload, accelerating it over a period of hours, before suddenly flinging the satellite into space at 23 times the speed of sound. The satellites would be engineered to withstand the g-forces encountered (2,000 g), and be cased in an aerodynamic shell. A two-year study has been commisioned and will begin within a few weeks at LaunchPoint Technologies in Goleta, California." New Scientist points out that if such a launch ring were built, it would instantly become "one of the most important targets on the planet."

Comments

"Moon is a Harsh Mistress" anybody??

[Churla]

Am I the only one seeing the parallel?

Re:"Moon is a Harsh Mistress" anybody??

[Bob-taro]

Just fill the passenger compartment (and passenger's lungs) with an 02 saturated liquid and accelleration ceases to be an issue.

Sounds good at first, but look what happens in a lab centrifuge -- you'd probably wind up with all your tissues separated into layers of equal density (with the "O2 saturated liquid" somewhere in the middle)!

Re:"Moon is a Harsh Mistress" anybody??

[doctor_nation]

I was at a presentation last week by the guys in this article.

The track design is based on particle colliders, so the entire thing is evacuated. Part of it is a rough vacuum and part is a hard vaccum (the actual track). The rough vacuum is because they have to limit thermal transfer to their super-cooled superconducting magnets.

The acceleration is actually not linear- it's radial. Going around a 2km track at 10km/s has some hefty acceleration associated with it. When ejected into the atmosphere, the projectile shouldn't immediately slow a great deal, although it will lose a lot of momentum before leaving the atmosphere. The design is a very long and skinny cone, to reduce thermal heating and drag force.

The best thing about this design for a launcher is that it doesn't require a lot of instantaneous power, unlike a linear accelerator. You can accelerate slowly.

Also, did anyone else immediately think of Xenogears when they saw this?

Re:"Moon is a Harsh Mistress" anybody??

[theshowmecanuck]

Only if your bouyancy is zero and there are no external forces acting on your system. Take blood cells in blood for example: put the blood in a centrafuge and spin it up to speed. The blood cells end up in the bottom of the test tube. That would be you in the launch ring. Except at many thousand Gs, you would look more like the blood cells in the bottom of the test tube than like you.

Lost in space

[nizo]

If the launch rate reached 3000 launches per year, they calculate that would drop to $189 per kilogram. Today, it costs more than 100 times that to send payloads into space.

However, Epstein says he cannot imagine a demand for that many launches in the foreseeable future.

Space burials (presumably of cremated remains). At $200 each (plus cremation) I am sure they could sell a few thousand of these per year. Now if they could only figure out a way to allow living people to withstand 2000g of acceleration, space tourism might actually be affordable.

Re:Lost in space

[mypalmike]

I can't see any drawbacks in dumping nuclear waste into space.

Indeed. Also, accelerating it in a 2km circle over several hours to 23 times the speed of sound is not fraught with peril.

Re:Lost in space

[megaditto]

You are confusing pressure with acceleration. These are not the same.

How cool is that? Intercontinental catapults

[patrixmyth]

We could fling refrigerators at North Korea! How's that missile testing going, Kim, did we mention we can launch frigidaire's into orbit? I'd prefer launching cows in homage to Monty Python and the Holy Grail, but at 2000g, that would probably equate to throwing hamburger.

Mass drivers RULE!

[Quiet_Desperation]

Yes!

As for it being a target, fuck that. Full steam ahead.

If we're not driving payloads into space at Mach 23 within 10 years, the terrorists have already won. Or something.

"one of the most important targets on the planet"

[k4_pacific]

If this ring is going to be "one of the most important targets on the planet", maybe they should build it as a series of concentric rings instead of a single ring. Perhaps havethe rings use alternating colors.

one ring to launch them all

[m0llusk]

One ring to launch them all,
one ring to fling them.
One ring to send them into space,
and into that darkness bring them.

A few points

[argStyopa]

First the FUD:
New Scientist points out that if such a launch ring were built, it would instantly become "one of the most important targets on the planet.
What a moronic comment.

You have a STATIC launcher.
It can toss things into ballistic trajectories.
One at a time.
With a warm-up of TENS OF HOURS.

I don't know if New Scientist realized this, but we have launch technologies that are
a) less vulnerable
b) more accurate
c) mobile
and
d) a little quicker to fire than that.

On another note, and not that this will mollify the crowd that fears a weapon in every technology, but in regards to the difficulty of punching something through the atmosphere at Mach 23, I seem to recall SDI experiments where a high-power laser was used to heat a 'track' through the atmosphere (in that case, to fire a particle beam weapon down the track with less atmospheric attenuation ). Couldn't a similar idea significantly reduce the air resistance for this sort of a projectile?

a_c = - \omega^2 r

[Kadin2048]

Except that the proposed design accelerates the payload around in a circle -- using magnets arranged inside a torus -- not a long straight runway. I doubt a linear runway would be practical; it would just be too long. The advantage of a torus is you can keep using the same magnets to accelerate the payload, over and over, until you've reached sufficient speed to let it fly.

Unless the circle was ridiculously large (probably the size of a continent or better), you're not going to be able to get up to escape velocity before you'd (as a human being) would be crushed by the effects of the centripetal acceleration.

I'm not going to do the math right now, but I'm pretty confident that of the 6,000 Gs they're quoting, most of them are in the radial direction and not in the tangential, so that even if you brought the payload up to speed slowly, you'd still be crushed. It would be just like being in a centrifuge.

Re:a_c = - \omega^2 r

[MConlon]

Of course, there's going to be a bit of bump when the capsule hits the atmosphere, and there's also the bit of a trick about getting the thing oriented so the capsule if flung upward...

You don't need to fling the capsule upwards, you need to fling it horizontally such that it doesn't hit anything. To get into orbit you do not go "up", you go sideways as fast as you can. The advantages of being high up are:

1. the atmosphere is thinner which means there is less aerodynamic drag on your vehicle, and
2. there are less things to hit.

Being "in orbit" is essentially falling without ever hitting the ground.

MJC

Ablative coating

[maddogsparky]

The reason that most meteors don't hit the ground is because they are so small. The one that do hit the ground and are found right away often have FROST on them since they were so cold in space. As for exploding into a million pieces, meteors aren't designed for reentry.

Any compentent aeroshell engineer could design a case that would protect the payload (such as a capsule covered with the stuff they use for ablatively cooling rocket nozzles). The big concern usually with burning through airframes isn't that we don't have materials that can withstand the heat and friction; it is that those materials typically aren't very light-weight or are too expensive.

Besides, once the track is set up, it should be easy to try out new aeroshell designs! One of the stumbling blocks right now is trying to accellerate a test article to high enough speeds. Very often, they stick a test article on a sounding rocket that sends back data during re-entry.

And yes, IAARS.

Bad math?

[Bender0x7D1]

Am I crazy, or did they get the math wrong in the article?

The acceleration equation for circular motion is: a = v^2 / r

We are given:

Velocity: 10 kilometers/s

Width of ring = 2 kilometers, so radius = 1 kilometer

So:
v = 10,000 m/s
r = 1,000 m

a = (10,000 m/s * 10,000 m/s) / (1,000 meters) = 100,000 m/s^2

The acceleration due to gravity is about 10 m/s^2

This gives: (100,000 m/s^2) / (10 m/s^2) = 10,000 g

So it seems that their 2,000 g is way off. Even if we use 2 km for the radius it is still 5,000 g.

Re:Bad math?

[doctor_nation]

Your math is correct. I have an abstract from a presentation these guys gave last week and it lists the radial force at 20 MN (that's mega-Newtons) for a 200 kg projectile = 10,000 G. They don't list the acceleration in G anywhere so it's probably a New Scientist math error.

Re:Sounds Good, except

[NoData]

I know there's a relationship between bird migration and magnetic fields, too, as a lot of them blindly smack into the brick walls at a local MRI center.

Cute, but you gotta be kidding. I work with a 3T research MRI magnetic. Both the machine and the facility are heavily shielded, and the field drop-off is very steep. While the isocenter of the bore is at 3 Tesla (30,000 Gauss), the 5 Gauss line is only a few meters (about 5 in the axial direction, 3 in the radial direction) from the isocenter. By comparison, a kitchen magnet is maybe 100-250 Gauss.