Solar thermal propulsion | Propulsion Workgroup | Forum

Thanks very much for posting this!  I hadn't heard of Solar Thermal Propulsion before, it was interesting to read up on it.

Once we have the CLLARE mission specified in terms of abstract components (e.g. not in terms of units like "a LOX/LH2 chemical rocket with propellant capacity x kg" but in terms of "a propulsion module capable of imparting a delta-v of at least y m/s to a mass of z kg") then we will consider all available options to implement those components, and in the case of propulsion components, STP will be something to consider.

I am not too sure of the chances of it being suitable.  The Isp is fantastic – 800s is almost twice as good as the best LOX/LH2 engines.  But it seems like the thrust is quite low?  I've not read too much on the subject yet, but this site, claims they have "a thrust level around 10
to 100 N".  If our spacecraft has a mass on the order of 1000 kg, then this translates to just 0.01 m/s/s or 0.1 m/s/s of acceleration.  Assuming we get the higher 0.1 m/s/s acceleration, a TLI maneuver of delta-v about 3200 m/s will take 32000 s, or about 8 hours.  This is a long time, but perhaps not infeasibly long.  Of course, this is assuming the system can produce this thrust continuously – but over the course of 8 hours, the spacecraft is likely to orbit Earth several times, with the Earth possibly blocking a lot of the sunlight at some stages of the orbit, extending burn time.  It might still work out, though, I don't know enough to make an intuitive guess as to what the effects of this would be.  With the lower 0.01 m/s/s, however, we are talking 80 hours minimum.  That sort of acceleration for all of our burns would stretch the total mission out considerably, with significant implications for life support, etc.

All of the above, of course, is based on my first thoughts after my first reading about STP.  If you have a more detailed knowledge of the subject (which seems likely) and can correct any oversights I would love to hear about it.  Anything which can get us an Isp of 800s relatively simply (and STP seems conceptually fairly simple, at least compared to, say, VASIMR) is well worth considering, in my opinion!