Also, this paragraph from Stanislaw Lem's book Fiasco, which I'm reading at the moment:They would land, but first turn the Hermes into a comet. Out of valves in the hull that opened along the sides came a foam from tanks; inflated by injections of gas, the foam surrounded the entire vessel with a large cocoon of irregular, hardened bubbles. The Hermes, like a pit in a fruit, lay in a spongy mass of globules. Even from up close it looked like an elongated chunk of rock covered with craters. The burst bubbles made the surface resemble the crust of an asteroid bombarded for centuries by dust clouds and meteors. The drive, indispensable, would be the tail of the comet, which, as it approached the perihelion, would always be directed away from the sun, an illusion created by the drive deflectors. A precise spectral analysis would have revealed, of course, a pulse and composition of gases not found in any comet. But nothing could be done about that.