Make the ISS a VASIMR-powered spaceship?

[francisdrake]

Recently I read in the news:
"NASA and Ad Astra Rocket Company of Webster, Texas, have signed a Space Act Agreement that could lead to the testing of a new plasma-based space propulsion technology on the International Space Station. The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) engine initially was studied by NASA and is being commercially developed by Ad Astra."

The VASIMR engine shall be used for boosting the ISS orbit. Electrical power for short boosts is supplied by batteries, being trickle-charged from the stations solar panels.

On the Ad Astra homepage a visionary concept is discussed, to make the whole ISS a VASIMR-driven spaceship in some distant future. The advantage would be, that the ISS is already in orbit and is capable of accomodating a crew on long-duration missions.

- Do you think this a realistic option?

- Can the station withstand the required acceleration without breaking appart?

- Would the solar panels provide sufficient electrical power to supply the engines continously? (How much power is needed per 1 Newton of thrust?)

I understand orbit boosting requires very little acceleration, but going to the moon (or beyond ) will probably require a higher thrust level.

The Europeans have spiraled-up the ion-driven SMART-1 satellite to the moon, having 366 kg mass and only 70 milliNewton thrust, taking about 2 months to reach moon orbit. So technically it might be possible ...

 

[Urwumpe]

- Do you think this a realistic option?

Yeah, but I am not sure the excess power available currently is enough for keeping the orbit stable.

- Can the station withstand the required acceleration without breaking appart?

Easily. The shuttle produces about 4 * 387 N during reboosts, should be no problem to have much lower loads.

 

[garyw]

Yeah, but I am not sure the excess power available currently is enough for keeping the orbit stable.

It isn't. The ISS is missing several solar arrays which would have let to a power surplus. Even with STS-119 delivering the final array they are still going to be on a tight power budget.

 

[steph]

There's still the penalty of flying the fuel up to the station. But I can hardly imagine that a small VASIMR could do anything else than an orbit boost. And there's the Van Allen problem. If it's manned, you can't spiral it up slowly without exposing the crew to dangerous radiation levels. They'd have to put the crew only after the station has reached a certain height.
Besides these,there's the before mentioned problem of power. If it's hard to get enough power for an orbit boost, imagine how hard it would be to get power for, say, a moonshot. They'd probably need some other power source, not the solar panels.

 

[Woo482]

I am sure some one started a thread on this a few days ago and how much power will this use up ?

 

[garyw]

There's still the penalty of flying the fuel up to the station. But I can hardly imagine that a small VASIMR could do anything else than an orbit boost. And there's the Van Allen problem. If it's manned, you can't spiral it up slowly without exposing the crew to dangerous radiation levels. They'd have to put the crew only after the station has reached a certain height.
Besides these,there's the before mentioned problem of power. If it's hard to get enough power for an orbit boost, imagine how hard it would be to get power for, say, a moonshot. They'd probably need some other power source, not the solar panels.

Max height limit for the ISS is 400KM. Above that Soyuz has issues getting to the ISS for crew changes. The VASIMR engine will be for reboost only.


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I am sure some one started a thread on this a few days ago and how much power will this use up ?

They are looking at 200kW.

 

[Jarvitä]

They'd probably need some other power source, not the solar panels.

They could power it with a nuclear reactor. It's not as if it hasn't been done before, both the USA and Russia have done it.

 

[garyw]

They could power it with a nuclear reactor. It's not as if it hasn't been done before, both the USA and Russia have done it.

Won't happen. Way too many risks.

The plan is for the engine to have it's own next generation solar array which will provide most of the power.

 

[francisdrake]

I downloaded Chang-Diaz paper on a VASIMR powered Mars mission:
http://ston.jsc.nasa.gov/collections/TRS/_techrep/TP-1995-3539.pdf , 270 kB.

It is based on engines with about 3 MW power consumption, pretty much if it was running on solar power.

The solar constant (=strength of the sun radiation) at earth orbit averages at 1366 W/m². With a solar cell efficiency of 20% (which seems pretty good by todays standards) this would require a solar array area of 3,000,000 / 1366 / 0.2 = 10980 m²

Based on one solar array 'wing' being 36 x 12 = 432 m² this would require 25 (additional ?) solar arrays on the ISS to power one engine (of unknown thrust).

On the other hand, putting a reactor to manned spacecraft might not be a realistic option within the ISS's lifespan ...

 

[Andy44]

Putting another reactor into LEO isn't a realistic option politically, either. Even using one beyond LEO would be tough these days.

 

[WombatControl]

I thought that the ISS was fairly well shielded against radiation from the Van Allen belts since its orbit passes through the South Atlantic Anomaly? Would that shielding be sufficient to allow the ISS to achieve higher orbits provided there were a vehicle capable of resupply?