The X3 Ion Engine Test Break Thrust Records

Universe Today ^ | 10/27/2017 | Matt Williams

[BenLurkin]

Not only would engines that are capable of achieving a great deal of thrust using less fuel be cost-effective, they will be able to ferry astronauts to destinations like Mars and beyond in less time.

This is where engines like the X3 Hall-effect thruster comes into play. This thruster, which is being developed by NASA’s Glenn Research Center in conjunction with the US Air Force and the University of Michigan, is a scaled-up model of the kinds of thrusters used by the Dawn spacecraft. During a recent test, this thruster shattered the previous record for a Hall-effect thruster, achieving higher power and superior thrust.

Hall-effect thrusters have garnered favor with mission planners in recent years because of their extreme efficiency. They function by turning small amounts of propellant (usually inert gases like xenon) into charged plasma with electrical fields, which is then accelerated very quickly using a magnetic field. Compared to chemical rockets, they can achieve top speeds using a tiny fraction of their fuel.

However, a major challenge so far has been building a Hall-effect thruster that is capable of achieving high levels of thrust as well. While fuel efficient, conventional ion engines typically produce only a fraction of the thrust produced by rockets that rely on solid-chemical propellants.

...

In recent tests, the X3 shattered the previous thrust record set by a Hall thruster, achieving 5.4 newtons of force compared with the old record of 3.3 newtons. The X3 also more than doubled the operating current (250 amperes vs. 112 amperes) and ran at a slightly higher power than the previous record-holder (102 kilowatts vs. 98 kilowatts). This was encouraging news, since it means that the engine can offer faster acceleration, which means shorter travel times.

[T-Bone Texan]

Wow. You remembered that off the top of your head? I am impressed.

I ran it through an online converter.

PS you were off by .3008, about.

[Imnidiot]

“Newton is not a power measure. It’s a force measure”

F orce +
I nertia +
G ravity =
________________
Newton...yumm

[trebb]

Had to look it up - except for the fact that a little over a loooong period adds up to a lot, it takes a slight modification of mindset to see why this is exciting news. If this engine was working against my little 4 cylinder engine, I wouldn’t notice it and might get 1/100 of a mile less per gallon....

[rarestia]

The challenge with this engine isn’t what it can do. The numbers on the engine itself are impressive. A human-rated transport is going to have much higher mass compared to a satellite or unmanned vessel. That level of thrust might be constant, but the thrust-to-weight (TWR) is going to be drastically different from their test beds.

The biggest component to interplanetary travel is not “getting up to speed.” The biggest component is slowing down. Once they get to Mars, they’re either going to have to aerobrake through the thin Martian atmosphere to circularize, or they’re going to have to turn the ship around and thrust retrograde to capture. They’ll just skip past Mars and out into the open solar system if their travel speed is higher than the orbital velocity.

[SunkenCiv]

The only ways to land on Mars have been developed in order to cope with the thin atmosphere, but the SpaceX proposal includes some aerobraking, with a propulsive finale. The variety of other approaches that have been used to land unmanned probes is remarkable.

Slowing down for gravitational capture at Mars will have to use chemical propulsion, but getting there in a reasonable timeframe with human passengers is a must, and will indeed require the kind of velocity that chemical propulsion can yield.

The specific impullse of an ion drive is high, and it has a very long "burn time", making it ideally suited for interstellar probes (assuming everyone is up for a very, very long wait), but specific impulse is often trotted out as if it is the only measurement that means anything.

Specific impulse of liquid fueled engines is higher, generally, than solid rocket boosters, but SRBs can put large payloads into high altitude, and probably all the way to orbit, cheaper, and have a demonstrated reusability further lowering cost. The Shuttle couldn't get off the ground without SRBs, and the SLS now under (re)devvelopment is slated to use warmed-over versions of the Shuttle's main engines (liquid, cryo), but won't be able to get off the ground without SRBs -- and those SRBs are merely longer versions of those used on the Shuttle. It would make more sense to ditch the liquid-fueled first stage and just go with four SRBs. That wouldn't put pork in the barrel, however.

[rarestia]

Those chemical prop burns are going to require schlepping that fuel across the solar system. Aerobraking should be sufficient to slow for a highly-elliptical orbit with successive loops through the atmosphere until entry, but I agree that some chemical propulsion will be needed. The question in my mind is “how much?”

High ISP is great in a vacuum but means nothing in atmosphere. They’ll probably use Merlins or the new Raptors to leave the Martian surface. I don’t know the ISP on them, but LRBs are usually lower than high ISP/low thrust propulsion like ion drives.