[AR] partly-electric propulsion (was Re: Zubrin,)
- From: Keith Henson <hkeithhenson@xxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Thu, 5 Sep 2019 08:03:26 -0700
On Wed, Sep 4, 2019 at 10:08 PM Henry Spencer <hspencer@xxxxxxxxxxxxx> wrote:
snip
And third, compared to chemical rocket engines, electrical hardware is
*VERY* heavy for the amount of power it handles.
As usual, Henry is dead-on correct. I ran into this problem when
trying to use VASMR engines to lift power satellite parts above LEO.
The power conditioning (RF generator) mass ate the payload. I finally
found a lightweight arcjet which was not intended as a rocket engine.
Picture of one attached. The mass is on the order of a 100 kg and the
power is 50 MW, which puts it into the chemical rocket class if you
don't consider the much more massive power supply or the cooling.
According to the guy who runs it, 70% of the electrical energy wind up
as Ke in the exhaust.
Still, the advantages of 20 km/s exhaust velocity might make up for
the power supply mass. Neither the power or the cooling is a problem
for a power satellite to self-power from a construction orbit out to
GEO.
If not self-powering, beamed 25 GHz microwave at around 10 kW/m^2
might work. There is enough interest in beamed energy in space that
the Feds sent out an RFI a few days ago.
https://www.fbo.gov/index?s=opportunity&mode=form&id=3fce400569bea98cb88d7a9c759823dc&tab=core&_cview=0
Keith
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