Comments on: The Science Behind ‘The Martian’ Hermes Spacecraft

By: Cody Freilinger

Cody Freilinger — Tue, 10 Apr 2018 19:42:34 +0000

Like your language

By: Jason G

Jason G — Tue, 25 Jul 2017 22:44:54 +0000

Not necessarily a retrograde orbit, could be a -V pointed attitude… Can’t tell direction of flight from a still image (though to be fair, in the movie, they were always flying “forward”) 🙂

By: Brian Koberlein

Brian Koberlein — Mon, 15 May 2017 17:31:00 +0000

It generates artificial gravity via centripetal force.

By: G.Daddy

G.Daddy — Mon, 15 May 2017 11:06:54 +0000

I just wanted to know why the large center ring spun.

By: Charles

Charles — Fri, 28 Apr 2017 14:55:59 +0000

Yes – all sorts of practical problems with how spacious that ship was, but I let it slide on the assumption that a lot of that space would have been filled with supplies on the outbound trip (Even the enormous and spacious gym they had!)

The dust storm was a huge issue in both the film and the book – pure artistic licence. The book did go into some of the other problems/issues in much more details that the film.

Possibly re-trying the potatoes would have been harder because all the water would have sublimated too – not enough left to re-establish the ‘farm’ a second time.

By: samgrog

samgrog — Sun, 16 Apr 2017 16:10:54 +0000

The thing is that there is no possible way for the storms to blow stuff around in the first place: there isn’t enough pressure. Now I know there are storms, but how would one blow over a piece of paper, much less a spacecraft? I love the book, but it just makes me sad that it doesn’t make enough sense.

By: Brian Koberlein

Brian Koberlein — Sun, 13 Nov 2016 20:18:24 +0000

The Martian storm idea is something the author Andy Weir admitted wasn’t accurate. It was left as a plot device in the movie. The size of Hermes is something that can be debated, since it is intended as a large, multi-mission shuttle between Earth and Mars. Watney actually wouldn’t explode, even if exposed to vacuum. Human bodies are more robust than that. The issue with the potatoes was not the bacteria, but that flash freezing killed the potatoes, so they wouldn’t sprout again even with bacteria.

There are areas of the book and movie where technical flaws can be pointed out, but to say it’s barely more accurate than Star Wars is rubbish.

By: Kirk

Kirk — Sun, 13 Nov 2016 16:22:50 +0000

The science on the movie is a joke. I like the movie, but it’s barely more accurate than Star Wars. Dust storms don’t produce near enough force to knock over a spacecraft. It’s like talc in the air, and at next to no pressure, it has no force. As for the Hermes, they show 8 foot wide hallways and 10 feet of space around a dining table, people floating through the craft with room to spread their arms and look out the giant windows. This thing has more unoccupied space than my house. Spacecraft are cramped and room is at a premium. This is not how a spacecraft would be built unless you were looking to waste hundreds of billions of dollars. Watney also says he would “implode” if the hab leaked, but he would explode, since the pressure in his body is higher than the atmospheric pressure. In stead of starving for almost a year after the hab exploded, which it wouldn’t do, why wouldn’t he grow more potatoes? It worked the first time, and he has more of his dooty than there was of all the others when he did it the first time. He should have been able to just start over. I wish just once the makers of movies would get good technical advice before finishing.

By: hopdavid

hopdavid — Fri, 16 Sep 2016 16:17:24 +0000

Yes, ion has great ISP. 30 km/s is a plausible exhaust velocity. However an ion engine’s delta V budget from LEO to LMO would be around 15 km/s under the best of circumstances. For a quicker trip to Mars, the delta V budget could easily be 30 km/s.

Can you plug these numbers into the rocket equation? I am guessing that’s beyond your pay grade.

By: hopdavid

hopdavid — Fri, 16 Sep 2016 16:07:26 +0000

Henry Morgan writes “Do you know anything about orbital physics? Coming in on a Hohmann-like orbit from mars, the Hermes would be in a parabolic orbit with a periapsis close to the surface of Earth.”

Completely wrong. Coming from Mars on a Hohmann transfer, the Hermes would enter earth’s sphere of influence on a hyperbolic orbit wrt to earth. The hyperbolic excess velocity would be in the neighborhood of 3 km/s.

To answer your question, yes I do know something about orbital physics. You, on the other hand, do not.

By: Johnathan Van Hatten

Johnathan Van Hatten — Tue, 08 Mar 2016 10:10:23 +0000

Did anybody notice that in the image, the Hermes is in a retrograde orbit? If that’s the coast of Mexico, and the launch vehicle was fired from Cape Canaveral, then the Hermes is in a retrograde transfer orbit, which adds almost 1km/s of delta-V to the launch vessel. Just pointing that out. Perhaps the Martian transfer orbit was retrograde, that could make sense.

By: Henry Morgan

Henry Morgan — Sat, 16 Jan 2016 19:41:55 +0000

The second half of your comment is also pretty bullshit. The Hermes uses ion engines which use relatively (compared to chemical rockets) little fuel because of their ridiculously high ISP. While jerk (change in acceleration over time) would play a part, with ion engines, the TWR wouldn’t change very much between the initial and final states.