I understand that solar sails have just recently been progressing to be of use. Could the solar sails be positioned to create a hyperbolic mirror to super heat a substance to produce propulsion along with being orientated to propel off the sun?

  • $\begingroup$ related:space.stackexchange.com/questions/28386/… $\endgroup$ Commented Mar 19 at 2:55
  • $\begingroup$ You can collect the energy with solar panels to drive a thermal rocket: steamjet.space $\endgroup$
    – John Doty
    Commented Mar 19 at 21:10
  • $\begingroup$ Please clarify your objective. In interplanetary flight, Solar sails are usually optimized to produce radial thrust (away from the Sun) whereas reactive trust (chemical, thermal nuclear, ionic) are usually oriented to produce thrust tangential to a heliocentric orbit to produce Hohmann transfers. You looking for apples, or oranges? $\endgroup$
    – Woody
    Commented Mar 22 at 2:46
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    $\begingroup$ Great question! It's certainly possible as answer(s) point out. But you can also use the concentrated light to generate electricity (via photovoltaics (solar cells) or a Stirling Engine + generator) to power ion engines. Those would give you much more delta-v per kg of propellant than a solar thermal rocket. And if you are far from the Sun, it may be the only way. $\endgroup$
    – uhoh
    Commented Mar 24 at 0:12

1 Answer 1


Sounds a bit like a solar thermal rocket.

Here's a diagram of one from page 49 of Solar Rocket System Concept Analysis. It would use a pair of parabolic reflectors to use sunlight to heat propellant.

Solar rocket system diagram

The idea isn't new... this was from the late 70s, early 80s, but as far as I know no-one has actually proposed building one yet. I suspect their usefulness is a little limited, though a laser-driven relative might be more useful.

produce propulsion along with being orientated to propel off the sun?

you seem to be wanting to operate your rocket simultaneously in solar sail and solar thermal rocket mode, and whilst you technically could it is unlikely to gain you anything. The thrust of the solar sail part is extremely low relative to the actual rocket part, so it can't contribute to thrust, and the additional mass required to keep the whole ensemble stable whilst the rocket is operating is not something you want to have to drag around with a solar sail.

Trying to combine the two sounds like an awkward compromise, to say the least, and it isn't immediately obvious to me what sort of mission this spacecraft would be suitable for that wouldn't be better served with a plain old solar sail or solar-powered ion-drive spacecraft.


To put some actual numbers to the claim: the example spacecraft above has a pair of 100ft diameter collectors, giving a total area of ~1500m2 in sensible units. Given a solar irradiance of 1361 W/m2, and assuming the collectors act as perfect absorbers (which is the ideal behaviour for a solar thermal rocket), that gives a sunlight pressure of ~6.6mN. If they were perfect reflectors this doubles, but means you can't run the rocket. The linked paper gives example solar rocket thrusts between ~60N and ~400N... tens of thousands of times higher.

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    $\begingroup$ And it doesn't work at night... $\endgroup$
    – GdD
    Commented Mar 19 at 19:36
  • $\begingroup$ @Justintimeforfun did you read the links? $\endgroup$ Commented Mar 27 at 8:13
  • $\begingroup$ I did I was being funny. $\endgroup$ Commented Mar 27 at 13:27

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