There is no direct description of how the Hermes enters Mars and Earth orbits in the book. It may be safely assumed she is serviced and refueled in Earth's orbit in between the voyages. However, there are two distinct possibilities how EOI (Earth orbit insertion) is accomplished:

  • by (presumably head-on) aerobraking in the upper atmosphere (which puts stress on the structure of the ship and is kind of scary considering there's a used nuclear reactor aboard, but saves a lot of fuel);
  • by purely propulsive deceleration - the ship retrofires the VASIMR continuously.

Which of those alternatives is true in Weir's universe?

During the rendezvous scene, inner door of the airlock is blown up instead of the outer one and Commander Lewis says "I want the outer door unharmed so we keep our smooth aerobraking shape" (emphasis mine).

P.S. I've got a Random House version of the book.

1 Answer 1


The author has said that at both Earth and Mars there would be aerobraking.

"I imagined an Hermes as being a very large cone-shaped ship, like a super-sized Orion capsule. It was split down the middle and the two halves could separate, attached with cables, and spin to provide artificial gravity. It assumed the capsule shape to aerobrake at both Mars and Earth."


You can see an image of what he imagined here: http://www.galactanet.com/martian/hermes.png


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