Ad Astra to develop VASIMR lunar tug

[Sam Fraser]

Studies will be conducted to evaluate a Lunar Tug concept utilizing Variable Specific Impulse Magneto-plasma Rocket (VASIMR) engine capabilities from Low Earth Orbit to Lunar Orbit and libration points. NASA/JSC intends to purchase these services from Ad Astra Rocket Company.

https://www.fbo.gov/index?s=opportunity&mode=form&id=35a99fd8aa65c86cb633fe8940243aad&tab=core&_cview=0&cck=1&au=&ck=

There's an executive summary from Ad Astra:

http://www.adastrarocket.com/EXECUTIVE%20SUMMARY240110.pdf

The last paragraph is particularly interesting:

Another far-term application of the technology involves resource recovery from space, particularly water, from near Earth orbiting asteroids and comets. While these missions remain in the conceptual stage, in August of 2007, Ad Astra signed a contract with Excalibur Exploration Ltd., a British Company based in Douglas, Isle of Man, granting the latter the right of first refusal to acquire VASIMR engines for space resource recovery.

"Excalibur Exploration"?

[Rhyshaelkan]

As someone posted for me over at the nasaspaceflight forum.

http://www.periodictable.com/Properties/A/IonizationEnergies.html

It is rather a shame radon is radioactive. The higher the element weight the higher the Isp. The higher on the graph the easier it is to ionize. Thus Radon is a good candidate. Shame it is radioactive. But the question would be. How much radioactivity would actually be spread in the Earth Moon system and deep space? Does it compare at all to the amount of radiation poured into the Earth Moon system by the Sun?

However other nice notables on the list are Neon, Argon, Krypton, and Xenon.

I am rather holding a candle for oxygen though. Easier to ionize than hydrogen, heavier than hydrogen, a byproduct of Lunar mining. And quite possibly a product of asteroid mining too. Oxygen loves to bond with other elements and is 42% of the Moon.

[jsteele235]

http://www.periodictable.com/Properties/A/IonizationEnergies.html


However other nice notables on the list are Neon, Argon, Krypton, and Xenon.

I am rather holding a candle for oxygen though. Easier to ionize than hydrogen, heavier than hydrogen, a byproduct of Lunar mining. And quite possibly a product of asteroid mining too. Oxygen loves to bond with other elements and is 42% of the Moon.

If you sort the elements from your link by ionization energy, you will find that oxygen is a pretty poor choice. Potassium looks like a really good bet, and is available in the so-called KREEP (potassium/rare earth/phosphorous) minerals found on the moon. I'm all about high isp! I can't remember who said that a four digit isp is about as useful as a single digit IQ.

[Rhyshaelkan]

For surely I would rather use what is available, without relying on Earth for everything. Argon is lovely, Neon and Xenon even more so. However, I want to cut the leash. The sooner a suitable alternative to imported stuff from Earth the better.

I am not all about Isp. I want thrust and Isp. They say VASIMR can run in low or high gear mode. Cannot there be a balance. Power input, medium, rate of discharge. I love VASIMR but I think it could be done better.

All in all my argument is more and faster. Life is short. I would like to see it before I end.

[jsteele235]

I am not all about Isp. I want thrust and Isp. They say VASMIR can run in low or high gear mode. Cannot there be a balance. Power input, medium, rate of discharge. I love VASMIR but I think it could be done better.



Good point. The thrust you get from the current electric propulsion technologies is truly pitiful. Maybe a better figure of merit would combine Isp with thrust-to-weight ratio of engine. This could be a good candidate for an X-prize.

[Treefrog]

I was just reading in a VASIMR document (IEPC-2007-244) about how solar electric generating is ~3kg/kW.
Now for a 2MW VASIMR this means 6,000kg needs to be boosted into space but more importantly it's also another 6 tonnes to be accelerated to the Moon (or wherever) and back, with a delta V in the region of 3,000m/s.
Here's my question: why put the panels on the VASIMR-powered craft at all? Why not have them in Earth orbit, transmitting the power via e.g. microwaves to a receiver mounted on the Lunar Tug as has been suggested for solar power generation to be transmitted to Earth?
This has the following advantages that I see: less propellant usage and cost every trip; solar panels can be less sturdily-constructed (lighter); surplus power could be sold on; payload fraction of the Lunar Tug is higher.
And, assuming that this first lunar tug would be the first of many, having two, three, six or more orbiting solar panels, all of which would be used by all Tugs, seems more reliable as a continuously operating multiple-redundancy system.
The main difficulty I foresee could be the focussing and targeting of the microwave beam - although that's just a guess.

So that's what I was thinking - what do the more knowledgeable people think?