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Hermes Rotate ! by francisdrakex Hermes Rotate ! by francisdrakex
Hermes in Martian orbit thrusting and spinning. Unlike the movie version, this concept has no centrifuge ring or other moving parts to provide artificial gravity. With the engines pointed 'sideways' it can accelerate while the whole spinning ship is the centrifuge. The reactor with its shielding is the counterweight for the crew hab. The only downside is that the truss needs to be sturdy built to withstand the bending stress from the engines, and the heat radiator wings need a certain rigidity.

Note:
The rotational speed is exaggerated here. In reality it rotates only at 3 rpm to provide a Mars-like gravity in the hab.
The picture is composed from a series of screenshots made in the 'Orbiter' space flight simulator.

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:icondavidy12:
Davidy12 Featured By Owner Jan 16, 2016
Is this in orbiter 2010?
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:icondavidy12:
Davidy12 Featured By Owner Jan 16, 2016
NVM. Is it for DL
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:iconfrancisdrakex:
Yes, the screenshot was made in Orbiter 2010, with the hi-res Mars texture pack.
This is actually only the GMAX model imported into Orbiter and a simple config-file.
It is not an addon, so it cannot be downloaded.
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:iconmikusingularity:
mikusingularity Featured By Owner Oct 11, 2015
You should release this add-on! I love it!
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:iconsmpritchard:
SMPritchard Featured By Owner Oct 10, 2015  Professional Digital Artist
I don't think bending stress would be an issue at all, considering in the book the Hermes used some species of ion engine. Their thrust is barely noticeable.
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:iconfrancisdrakex:
francisdrakex Featured By Owner Oct 11, 2015
Agree. The thrust off all engines combined is like 200 N only, giving an acceleration of 2 mm/s².
A quick calculation gave me a bending stress of 2 N/mm² only, compared to a tensile stress (from the centrifugal force) of 80 N/mm². 
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:iconisaackuo:
IsaacKuo Featured By Owner Oct 7, 2015  Hobbyist Digital Artist
Nice! Rotational stability would be slightly better if the radiators were aligned with the plane of rotation, but that's a minor quibble. Still, aligning the radiators with the plane of rotation would largely eliminate the rigidity requirements.

You can eliminate the bending stress by placing the engines on one end or the other (either with the crew module or with the reactor). As a bonus, this lets you efficiently change the axis of rotation (along with direction of thrust) with cyclic throttling of the engines. It's basically similar to the way a helicopter controls, but with a single blade.

Here's an example of a single blade helicopter: youtu.be/mKR6dDHXEqE

I bring up the example of a single bladed helicopter because I've found from past discussions that a lot of people don't think it's possible to have stable controlled motion when thrust isn't aligned on the centerline. But what's really important is the average. Even though a thruster on the tip of the truss will not produce thrust along the centerline at any given moment, the tip sweeps out a circle. On average, the torque from when the thruster is at one position will be counterbalanced by the torque when the ship has rotated another 180 degrees.
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:iconfrancisdrakex:
francisdrakex Featured By Owner Oct 7, 2015
Good point to align the radiators in the rotational plane! I did not do it as the engine pods can be oriented into a fore-and-aft direction, to allow linear maneuvers as well. This would lead to the exhausts blowing onto the radiators if the engines point in reactor direction. 
This could be avoided if the engines can only fire sideways or in hab direction. Any negative linear thrust during approach and docking would then have to come from the RCS. I will give that a closer examination.
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:iconnyrathwiz:
NyrathWiz Featured By Owner Oct 7, 2015  Hobbyist Digital Artist
A good old Heinlein "tumbling pigeon". No moving parts (which make a centrifuge a maintenance nightmare). Far superior to the movie design
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:iconfrancisdrakex:
francisdrakex Featured By Owner Oct 11, 2015
Thanks for your extensive coverage of Hermes designs on the Atomic Rockets website! www.projectrho.com/public_html…
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:iconcenturion030:
Centurion030 Featured By Owner Oct 9, 2015
That is a neat way to get artificial gravity without the moving parts!
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:iconi-phillip:
I-Phillip Featured By Owner Oct 8, 2015
Entirely agreed, though I love the film adaptation, I think it could have benefited greatly from a more plausible and scientifically accurate design for the Hermes, like the one Francisdrakex has created. 

The use of such a realistic and plausible design would probably have given the movie more of an Apollo 13 feel, than a sci-fi adventure drama thingie. 
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