# Can you use a light sail to achieve a survivable landing anyplace in our solar system?

Current answers at the new question Can you launch a probe to the Moon using a laser propelled craft? points out getting to the moon is not the problem, landing on it is.

This answer suggests that you can achieve escape velocity from Deimos using a bike and a ramp. If you can launch a bike presumably you can land it safely.

In theory you could use a light sail to put yourself in orbit around Deimos. You should also then be able to use it to lower your orbital speed so you touch down.

Is it possible to use a light sail to achieve a touch down survivable for a human? (Not sure what this would be, I saw several limits, but not sure how to translate that into something here)

• – James Jenkins Jun 12 '16 at 10:35

So the minimum speed you would have for impact with Deimos would be the same as the speed of a circular orbit at the surface, with higher points better. Lets be optimistic and say that above the mean radius of $6.2\text{km}$, there's a hill with an altitude of $0.4\text{km}$ (wild overoptimistic guess). The mass of the moon is more than $1.4 \times 10^{15}\text{kg}$. That makes the landing speed: $$v = \sqrt{\frac{GM}{r}}$$ $$v = \sqrt{\frac{(6.67\times 10^{-11} \text{N m}^2\text{kg}^{-2})(1.4\times10^{15}\text{kg})}{(6.6\text{km})}}$$ $$v = 3.8\text{m/s}$$