First Exotic Space Thruster Test Ends in Explosion

KentuckyFC writes "A NASA-funded test of an entirely new way to control orbiting satellites has ended with the prototype arcing dangerously and parts of the machine exploding. The new propulsion system is based on the Lorentz force: that a charged particle moving through a magnetic field experiences a force perpendicular to both its velocity and the field. So the plan is to ensure that a satellite passing though the Earth's magnetic field is electrically charged so as to generate a force that can be used to steer the spacecraft. The advantage of the idea is that it requires no propellant, which is a big deal since most satellites' lifespans are limited by the amount of fuel they can carry. But the first ground-based tests haven't gone entirely to plan."

Jazzing up the story a bit

[Goaway]

As much as we all like a good explosion, that summary seems highly misleading. From the abstract:

Microscopic arcing was observed at voltages as low as -300 V. This arcing caused solder to explode off of the object. Insulating the object allowed the charge to remain on the object longer, while in the plasma, and also eliminated the arcing. However, this insulation does not allow a net charge to reside on the surface of the spacecraft.

"Caused solder to explode off the object" hardly sounds like much of an explosion.

Another variant also had problems.

[Ungrounded Lightning]

Another variant of this is to have two weights connected by a wire tether and tide-locked to the primary, so the wire is oriented at roughly right angles to the orbit. Then you put a current in the wire by ejecting electrons on one end and collecting them at the other - making it into a motor that can accelerate or decelerate along the orbit. No reaction mass, run it off the solar collectors, etc. This also ran into issues with arcing.

They tried an experiment on this with the shuttle and a tether to a satellite they were launching, and found a problem: The motion along the orbit also causes it to act like a generator, powered by the orbital momentum. (This was known - and also has possible uses.) This produces a voltage gradient along the wire tether. So the tether has to be insulated to prevent arcing to the very low-pressure plasma that constitutes the high atmosphere and solar wind.

What they discovered was that minute flaws in the insulation caused localized arcs to the surrounding plasma. These were powered by the orbital motion relative to the earth's field and were very intense. They quickly melted through the thin tether.

So such a motor is not an impossibility. But it will require some heavy engineering work to get around this problem.

(It also says that large-scale tethered orbital structures have an additional problem to be solved: Keeping the tethers intact despite kilovolts of induced voltage along the tether and the resulting arcing.)

It's easy to think of space as filled with a hard vacuum. Unfortunately it's actually filled with very low pressure conductive plasma and near the Earth that's dense enough to be a major engineering issue.

Refueling

[visible.frylock]

I was surprised to learn that satellites are not refueled more often. After a bit of googling, this pdf [dtic.mil] came up. From page 15:

Although the use of shuttle manned EVA evolutions to conduct on-orbit servicing has proven sucessful in LEO, shuttle operational limits preclude operations above 400nm. Satellites which operate in MEO or GEO with typical altitudes of as high as 22,000 nm are not accessible to shuttle flights at this time.

This was from 1996, but as I understand, basic shuttle capabilities haven't changed much (someone correct me if I'm wrong). I think nm is nautical mile (1.852km).

Re:dependant on earth's magnetic field?

[dvase]

Will this screw up when the earths field begins fluctuating when poles being going into reversal again?

Seeing as the force generated is in a direction perpendicular to both the satellite's direction and the magnetic field lines, it really shouldn't have a major effect.

As long as the magnetic field stays at least somewhat parallel to the earth's surface, a lift force will be generated regardless of the field polarity.

Of course, if there is zero magnetic field that means no lift force, but that doesn't mean things immediately fall out of the sky, only the potential to drop a little in orbit until the field picks up again.

Re:Another variant also had problems.

[Jesus_666]

So the lesson is "moving something by ionizing part of it is pretty hard to do in a conductive medium". Another lesson people tend to forget is "space research is all about blowing up things until you get it right". A new propulsion technology not working as expected during the first few trials is not quite counterintuitive.

Re:Heh

[Anonymous Coward]

It's a valid method...just not inside the atmosphere.

Maybe the same can be said for prototype in TFA. arcing should be less common in space.

Re:It's Rocket Science

[CCFreak2K]

From Wikipedia [wikipedia.org]:

As with many rockets, the initial flights of each new Ariane model have seen failures. However, overall, the Ariane 4 and 5 are the most reliable commercial rockets ever launched. As of January 2006, 169 Ariane flights have boosted 290 satellites, successfully placing 271 of them on orbit (223 main passengers and 48 auxiliary passengers) for a total mass of 575 000 kg successfully delivered on orbit. This success rate also makes Arianespace the foremost commercial launcher; in some years, more than two thirds of all commercial satellites have been launched with the company's vehicles.

Re:Good for them

[DerekLyons]

I'm actually glad to see NASA doing stuff that might not work. It seems that a lot of the space work thats been happening in the last decade or two has been stuff that we know we can do.

NASA has never stopped doing stuff that might not work - it's just that 99.99% percent of what does (successful or not) never makes Slashdot, let alone the mainstream media. Heck, even most of the stuff that's made the mainstream media hasn't really been 'stuff we know how to do'... Pathfinder, Spirit, Opportunity. Deep Space 1, Deep Impact, the Hubble repair missions, quite of the ISS assembly flights... I could go on, but those alone should suffice.
 
 

There are still failures, but those tend to be metric vs imperial units issues, not because they're pushing forward in to new areas.

Had NASA suffered a failure because of a units error - you'd have a point. I assume you mean Mars Climate Orbiter - which was lost because NASA failed to analyze it's trajectory during the cruise phase. Not because of a units error. The units error was a contributing cause, but one trivially corrected for had standard monitoring been in place (both in testing and in flight) - but it wasn't because of sharp budget restrictions.
 
Not to be offensive, but it seems your impression of what NASA is or isn't doing seems to arise from not paying attention.

First Exotic Space Thruster Test Ends in Explosio

[__aahgmr7717]

Spacecraft charge has long been a problem with satellites. The OGO IV satellite (circa 1968) was frequently negative due to the fact that the electron temperature in the ionosphere is higher than the ion temperature. As such there is a net electron flow to the satellite until its charge repels the electrons for a balanced +/- flow. But this is not always the case since the solar panels on the craft have exposed electrical contacts. The charging panels can drive electrons away from the craft and give (every once in a while) a net positive charge to the craft. Plasmas are tricky beasts. Simulations of the space environment on earth are frequently wrong.

Re:A real arc

[Skapare]

The circuit breaker feeding the distribution wires (that were damaged in some way by an unknown cause) apparently failed. These distribution wires are running somewhere between 7200 and 19800 volts relative to ground. What is happening is that as the wires burn down in various places, that voltage is crossing over to the 120 volt (relative to ground) wires going into the homes. The insulation on the home wiring would be rated for 600 volts, which means they could fail with as little as 2400 volts or less. Circuit breakers in the homes are irrelevant. The wires going to the homes, the meters on the sides of the houses, the circuit breakers inside, and other wiring in the houses, are getting at least 7200 volts and arcing is happening even right through the insulation.

Assuming that the house does not actually catch fire and burn down (if it did, the firemen can do nothing about it until the power is confirmed to be permanently off), all of the wiring inside, circuit breakers, and electrical fixtures, will have to be replaced due to the damaged insulation.

Re:Heh

[kesuki]

I can just imagine sending an asteroid into Jupiter only for it to come out the other side and smack right into us.

It is a gas giant after all.

"Jupiter is thought to consist of a dense core with a mixture of elements, a surrounding layer of liquid metallic hydrogen with some helium, and an outer layer predominantly of molecular hydrogen.[23] Beyond this basic outline, there is still considerable uncertainty"

I think the liquid hydrogen will freeze and shatter any meteor we aim at jupiter... superheated in the atmosphere and then plunged into an ocean of metallic hydrogen...

besides there is believed to be at least and earth sized core, in some fiction, it's made entirely of diamond, but it probably isn't.