Author Topic: Vasimr: A true game changer? Role of Vasimir in future programs  (Read 103154 times)

Offline A_M_Swallow

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This is the dangerous sentence.
Quote
... In contrast, after 30 years of research, the VASIMR has only obtained about 50 percent efficiency in test stand burns of a few seconds’ duration, and that is only at high specific impulse.

For a 6 month burn the VASIMR needs to thrust for 6 * 32 * 24 * 60 * 60 = 16588800 seconds.
It sounds like the current VASIMRs cannot even thrust for a full minute.  That definitely needs fixing.

Offline baldusi

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This is the dangerous sentence.
Quote
... In contrast, after 30 years of research, the VASIMR has only obtained about 50 percent efficiency in test stand burns of a few seconds’ duration, and that is only at high specific impulse.

For a 6 month burn the VASIMR needs to thrust for 6 * 32 * 24 * 60 * 60 = 16588800 seconds.
It sounds like the current VASIMRs cannot even thrust for a full minute.  That definitely needs fixing.

The current vacuum chamber can't pump to keep the necessary vacuum for more than a minute. That's why they want to test it on the ISS. The ISS can't give enough power for more than 15 min, though. But that's an order of magnitude more testing. Besides, the ISS is a microgravity research lab. Unless the VASIMR was set to exactly offset the atmospheric drag, it might ruin some experiments.

Offline 8900

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Youtube video of the Mars Society's presentation
« Reply #142 on: 12/08/2011 12:47 pm »
Youtube video of the Mars Society's presentation


by the way, on the power per unit weight matter, I am not sure whether ISS solar panel is a good indicator. Do anyone know what is the efficiency of ISS solar panel? Given the fact that it is a Si based technology and it is produced in the 90s, I think we do have better, more efficient solar cells on the market (and surely will the efficiency continue to improve over time). So, maybe solar is the best partner of VASIMR not nuclear.
http://upload.wikimedia.org/wikipedia/commons/c/c9/PVeff%28rev111205%29.jpg
« Last Edit: 12/08/2011 01:12 pm by 8900 »

Offline spectre9

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Solar VASIMIR will not move much without panels 10x bigger than on the ISS even with new technology.

Good bump though  :P

Offline Robotbeat

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Solar VASIMIR will not move much without panels 10x bigger than on the ISS even with new technology.
...
Really? You must not have researched this, then! :)
ISS's total size is about the size of an American football field. That's 57600 ft^2. At 40% efficiency (new technology, remember?) and the insolation at 1AU of about 1500W/m^2, that works out to about 3 Megawatts. Most proposals for SEP tugs talk about power levels in the 500kW range, and even 150kW is useful.

The ISS's solar arrays are, compared to the state of the art nowadays, heavy and inefficient. A poor comparison point. Modern solar cells can operate at an efficiency level of four times ISS's cells (i.e. 40% versus 10%), and even the common commercial-level cells are 30% efficient.
« Last Edit: 12/08/2011 10:26 pm by Robotbeat »
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline 93143

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Does Zubrin really think Topaz is the best we can do?

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110009914_2011009270.pdf

Figure 5.  A 10 MW plant is predicted to have a system specific power of about 1 kWe/kg, including radiators.  Larger plants could have even higher specific powers.
« Last Edit: 12/08/2011 10:13 pm by 93143 »

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