Author Topic: Powerful Krypton Ion Engine/Mars SEP  (Read 22732 times)

Offline Twark_Main

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Re: Powerful Krypton Ion Engine/Mars SEP
« Reply #60 on: 07/15/2024 11:45 pm »
I seem to recall that 1kg/kw was current state of the art.

It's possible people are getting this from Wikipedia:

Quote from: Wikipedia
This is, however, far from the state of the art for flown spacecraft, which as of 2015 was 150 W/kg (6.7 kg/kW), and improving rapidly.[81] Very lightweight designs could likely achieve 1 kg/kW,[82]

Which cites this article without citations, which is a repost of this article with citations, which cites this 1994 SSI paper entitled "Low Mass Solar Power Satellite Built From Terrestrial or Lunar Materials."



The math from the paper is as follows:

7.5 micron thick Kapton "based on NASA figures for advanced substrates." Kapton has a density of 1.31-1.43 g/cm3, so we'll take the lower bound.

Solar cell efficiency of 11.5%, "based on NASA projections of achievable efficiencies for the 1990's."

Quote
The mass of the solar cell/transmitter array (including the substrate, but not the support structure) is just over 200 metric tons if Kapton is used for the substrate (terrestrial materials), and just under 800 tons if steel foil is used (lunar materials).

...which implies that the substrate + solar cells + integrated transmitter array has an area density 5/3rds that of the substrate alone.

Finally, we get to the line about 1 kg/kW:

Quote
If support structures can be redesigned which weigh about as much as a photovoltaic array built from terrestrial materials, then overall specific power levels of about 800 to 1000 watts per kilogram may be possible for a terrestrial SPS.

However the math on this does not follow, and this yields something like 0.21 kg/kW.  Obviously something is missing.



Does anyone have another source (preferably a newer source) for this 1 kg/kW figure?
« Last Edit: 07/15/2024 11:53 pm by Twark_Main »

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