Author Topic: Delta-Vs of Flown MMUs?  (Read 1738 times)

Offline Proponent

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Delta-Vs of Flown MMUs?
« on: 07/22/2009 03:54 AM »
Discussion of crewed missions to NEOs has me thinking about the nature of "landing" on such an object.

I'm thinking that for an NEO with an escape velocity on the order of 100 m/s (hence a diameter on the order of 100 km for an earth-like density), landing might be thought of as a docking operation.

If, on the other hand, the escape velocity is so low as to be of the order of magnitude of the delta-V of an MMU, then "landing" might best be executed as an EVA.

So, my question is, what have been the delta-Vs of MMUs flown in the past?

Even in the docking case, surface gravity would be so low (on the order of 0.01g) as to probably make an MMU desirable.

EDIT: Corrected surface gravity.
« Last Edit: 07/22/2009 04:45 AM by Proponent »

Offline joema

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Re: Delta-Vs of Flown MMUs?
« Reply #1 on: 07/22/2009 12:58 PM »
The Shuttle-era MMU used dry nitrogen thrusters and had total delta-v capability of 80 feet per second (24.4 meters/sec).

The Gemini-era AMU used hydrogen peroxide monopropellant, and had delta-V capability of about 250 feet per second (76.2 meters per second), roughly three times that of the MMU. It was flown only on Gemini 9. The AMU wasn't used on that mission because astronaut Cernan had various difficulties during the EVA.

The current SAFER unit is much smaller and straps on the outside of the life-support backpack, uses dry nitrogen, and has roughly 10 feet per second (3 meters per second) of delta-V. Unlike MMU/AMU, its purpose is contingency rescue only.

Offline Proponent

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Re: Delta-Vs of Flown MMUs?
« Reply #2 on: 07/22/2009 01:48 PM »
Assuming then that the MMU has a delta of 100 m/s and that we'd want to kept the size of the "de-orbit" burn to be done by the MMU down to 10 m/s, an MMU might be feasible for bodies smaller than about 10 km in diameter.

Tags: MMU