[time-nuts] GPS interference and history...
jfor at quikus.com
Fri Jan 13 00:32:41 EST 2012
Was this message relayed through a probe out about 3 light-months?
> On 6/9/11 1:06 PM, J. Forster wrote:
>> Nuclear power in space is poltically utterly impossible in the US. There
>> is huge opposition to RTGs, never mind even the thought of reactors.
> Hmm.. when I was working on Prometheus aka Jupiter Icy Moons Orbiter
> (JIMO) there was a guy from NASA HQ who gave a talk at the Lunar &
> Planetary Institute about flying reactors. His basic idea was that
> there is a fraction of people who will object to ANY nuclear power in
> orbit, be they 1 ounce Radioactive Heating Units (RHUs.. pretty much in
> every Mars mission we've flown) or RTGs or full on nuclear reactors
> (JIMO was going to fly a 300kWthermal/100kW electrical reactor being
> developed by the folks who do submarine reactors)
> So therefore, the "incremental pain" from flying a reactor is small.
>> Solar is not really practical either. The sun puts out about 1 KW/Sq.M
>> EO, and solar cell efficiency is<20%; so 10 KW needs 50 Sq.M of
>> stabilized pointing cells.
> A bit more than 1 kW/sq m (thats more like earth surface).. I think 1.3
> is more of a typical number above the atmosphere..
> 30% is more like what we get with triple junction enhanced solar cells,
> I think, but there's a whole lot of factors that go into it.
> In any case, there are lots of commercial COMSATs in GEO with tens of kW
> of solar panels (yes, many, many square meters). The power available on
> those things (to those of us used to deep space scientific missions) is
> gargantuan.. They're running more than a hundred TWTAs with hundreds of
> watts each. And the L band ones (Sirius/XM) are BIG tubes.
> But, for instance, Juno, which is on it's way to Jupiter has solar
> panels that are enormous (since it's NOT nuclear powered). ABout 60
> square meters which produce just under 500W at the orbit of Jupiter
> (5AU, so 1/25th what they generate at earth)..
> That would be about 200W/square meter in earth orbit (which I concede is
> about your 20%)
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