Quote from: Solman on 09/29/2011 11:08 pm Quote from: A_M_Swallow on 09/29/2011 04:33 am Providing it uses the same propellant solar thermal may be better for the RCS (Reaction Control System) than ion thrusters. RCS burns tend to be short where as SEP works better for extra long burns. I suspect that both can use Argon and nitrogen.



I remember seeing a paper from the Nineties that described a small working model of a solar thermal rocket concentrator that used fiberoptic cables to route the focussed sunlight to the engine.

This might be a good design for RCS thrusters using solar thermal.





Probably this article.

"Solar Thermal Propulsion for Small Spacecraft" PSI-SR-1228

by Takashi Nakamura et al.

http://www.psicorp.com/pdf/library/sr-1228.pdf



Thanks for the link. Carried to an extreme, fiber optics could be used to distribute heat and light to wherever its needed in a spacecraft. Perhaps the cable could be designed to shift the many frequencies of sunlight into a single frequency as it travels down the fiber optic line and deliver it to a PV element at the point where a device needs electricity. The PV element would be very efficient since it could be designed for a single frequency. The fiber optics could also provide data transfer and control of course. Cutting and welding using concentrated sunlight delivered by fiber optics also a possibility I would think.Large concentrators also enable a solar furnace for ISRU and they can double as microwave transmitters for space based power transmission between spacecraft or down to the surface of Mars for instance. They can be formed by a technique I call inflation insituform with degradable elements in which some parts harden when exposed to the Sun's UV light and other parts degrade. The finished product can be optimized for low mass - high specific power and can achieve very high temperatures if adjusted by built-in actuators both as it forms and thereafter. Or at least it seems practical to me.Another advantage of PV for concentrated sunlight is that the cells must be actively cooled and the resulting waste heat is useful for keeping spacecraft warm. This means nearly 100% of the intercepted sunlight is used compared to a regular PV array which must use some of its electricity to provide resistance heat and has lower efficiency to begin with. The support structure for the concentrator can be at least partially made of hollow tubes that could double as waste heat radiators perhaps.Steve