Electric Rockets Set To Transform Space Flight

An anonymous reader sends this quote from an article at Txchnologist: "The spectacle of a booster rocket lifting off a launch pad atop a mass of brilliant flames and billowing smoke is an iconic image of the Space Age. Such powerful chemical rockets are needed to break the bonds of Earth's gravity and send spacecraft into orbit. But once a vehicle has progressed beyond low-earth orbit chemical rockets are not necessarily the best way to get around outer space. That's because chemical propulsion systems require such large quantities of fuel to generate high speeds, there is little room for payload. As a result rocket scientists are increasingly turning to electric rockets, which accelerate propellants out the back end using solar-powered electromagnetic fields rather than chemical reactions. The electric rockets use so much less propellant that the entire spacecraft can be much more compact, which enables them to scale down the original launch boosters."

Comments

First electric post

[Spliffster]

Tesla would love this shit!

Ion Drive isn't new

[Anonymous Coward]

This is old technology and the benefits of this have already been realized in many satellites. There is literature going back well over a decade documenting the trade space.

Re:Ion Drive isn't new

[Anonymous Coward]

More like decades; quoted from Wikipedia,

The official father of the concept of electric propulsion is Konstantin Tsiolkovsky as he is the first to publish mention of the idea in 1911. However, the first documented instance where the possibility of electric propulsion is considered is found in Robert H. Goddard's handwritten notebook in an entry dated 6 September 1906. The first experiments with ion thrusters were carried out by Goddard at Clark University from 1916–1917.The technique was recommended for near-vacuum conditions at high altitude, but thrust was demonstrated with ionized air streams at atmospheric pressure. The idea appeared again in Hermann Oberth's "Wege zur Raumschiffahrt” (Ways to Spaceflight), published in 1923, where he explained his thoughts on the mass savings of electric propulsion, predicted its use in spacecraft propulsion and attitude control, and advocated electrostatic acceleration of charged gases.

A working ion thruster was built by Harold R. Kaufman in 1959 at the NASA Glenn Research Center facilities. It was similar to the general design of a gridded electrostatic ion thruster with mercury as its fuel. Suborbital tests of the engine followed during the 1960s and in 1964 the engine was sent into a suborbital flight aboard the Space Electric Rocket Test 1 (SERT 1). It successfully operated for the planned 31 minutes before falling back to Earth.

Re:Ion Drive isn't new

[tp1024]

The watt count doesn't matter. It's exhaust velocity (more means more energy use, no matter what technology) of the engine and the total amount of energy carried by the reactor (more energy means more mass, means less speed). 0.1-1% of the speed of light should easily be possible, but I haven't done the math to the point of calculating multiple stages, optimizing the energy budget with respect to the trade-off between exhaust velocity and energy consumption and so on and so forth.

Hydrogen-Oxygen fuel has an exhaust velocity of about 4500m/s for a final speed on the order of 20km/s with multiple stages (for any significant payload). Simple ion engines can reach 30,000m/s, but final speeds will be less than expected, as the empty mass of the stages is higher. Something on the order of 100km/s with 2-3 stages should be possible. (Let's say 12,000 years to Alpha Centauri.) More sophisticated engines can reach up to 200,000m/s in exhaust velocity (2000 years to Alpha Centauri), but somewhere the energy limitations will kick in and I don't know whether before or after that point. (That's when the Uranium/Plutonium makes up a very significant part of the deadweight - even if you throw some of it over board in the process.)

Just build some of space ships and a couple of pyramids in a desert to remind people they are on their way.

Re:Ion Drive isn't new

[tp1024]

Nope, just getting there. Think of it as a beeping monument in the sky.

A beeping monument with telescopes. The main justification would need to be astrometry, which you could do a hell of a lot better if you had a good telescope several hundred or thousand AU away from earth. Currently, we're doing all our triangulation with a 2AU long base (twice the distance earth-sun). Using the same 29cm telescope as Hipparcos, we could easily get 1000 times more accurate ranging data within mere decades.

It would be a revolution. True trigonometric measurements all the way to the other end of the galaxy, even the nearest neighboring galaxies, instead of the current guesswork based on guessing how bright a certain star is and thus how far it would need to be away in order to appear as bright as it does.

Ahh, the future

[squidflakes]

The best part about living where I live is that they are building VASMIR engines down the street. It would be a long walk, but I could still walk to a freaking starship drive factory.

Re:Ahh, the future

[Tumbleweed]

they are building VASMIR engines down the street. It would be a long walk, but ...

You may think that's a long walk, but that's peanuts compared to space.

Re:Do we even have such a long cord?

[decipher_saint]

213 million six foot power strips daisy chained together...

Surprised RTG powered probes dont use this.

[wisebabo]

I've actually been following ion powered (and all space flight) for a long time now and have wondered that ever since Deep Space 1 (no, not a TV series) "proved" the technology worked (that was one of its main jobs, it was a technology demonstrator) they didn't use ion engines on the space craft that used RTGs.

In particular New Horizons has travelled billions of miles coasting to Pluto, 99% of the time in hibernation despite the fact that its plutonium powered RTG is generating electricity whether used or not (it's not a reactor, it is always "on"). Considering the distance it has to travel, an ion drive could've really sped things up (or conversely allowed it to brake, and orbit Pluto!). Cassini might not have been such a good choice because maybe having the drive on doesn't allow good scientific observations (Cassini doesn't have its instruments on a scan tilt platform) and anyway the many delta - V changes might have required more thrust than the very weak ion drives can provide.

Actually, maybe ANY probe headed further than the moon or mars would find this useful. Juno, the Jupiter orbiter had huge solar panels which, during the cruise phase could have powered a decent ion engine. Messenger, the Mercury orbiter, although not going "far", had a huge delta-V requirement and had access to plenty of solar power.

Oh well, at least more and more probes like DAWN use this. I would presume when we return to the outer planets with any really ambitious probes (Europa lander/sub, Titan balloon/boat) they'll use this.

Someday, when we talk about sample return missions and the delta-V requirements at least double (and the fuel requirements go up geoemetrically!), ion drives (or their derivatives like the Vasimir drive) will be essential.

Re:Thought it was about VASIMR.

[Spy Handler]

I guess what I'm saying is he isn't a crank.

Actually, according to Rob Zubrin of Mars Society, he is one. The technology itself isn't a crank, it's real, but his claims (going to Mars in 39 days) and the big bucks he's soliciting are quite cranky.

To do what he's claiming, you would need to hook up the VASIMIR to a huge nuclear reactor. How do you get that reactor into orbit? You can't, not without a Nova type rocket bigger than a Saturn V. But if you had such a rocket, you could just blast off to Mars the old-fashioned way.

His other proposal is coupling a fusion reactor (which should be lighter than an equivalent fission one) to the VASIMIR. Well as we all know, fusion is always 20 years in the future.

Re:Do we even have such a long cord?

[ackthpt]

213 million six foot power strips daisy chained together...

The Fire Marshall will have an absolute conniption fit over that one.

Re:OT: Rocket Scientists Are Not Scientists

[ceoyoyo]

If you're building new drives to experiment with, you're a scientist. If you're following established principles to build a drive then you're an engineer.

The distinction isn't nearly as clear as you imply, and isn't based on your criteria.

I have degrees in oth science and engineering. Normally I do science with a bit of engineering, figuring out how to do new things. Sometimes I do engineering with a smattering of science figuring out how to do those new things out in the field.