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As the ISS has shown the ability for human habitation for extended periods, might we be able to add a propulsion unit to the ISS that would be capable of providing delta-v to send ISS to a martian orbit? Probably a low acceleration system that would allow for the maintenance of structural integrity would be needed.

A supply module with supplies sufficient for the Mars transit period would have to be added with the necessary supplies for the mission. If this presents structural or other problem, perhaps there could be resupply missions that could occur in Mars transit, or perhaps supply repositories placed in path of the ISS.

Likely, its power generating system like solar panels might have to be upgraded to meet internal energy needs at increased distance from the Sun.

Now a bit of an editorial for which I have been chastised in the past. This approach would take advantage of our proven capability of assembling a major structure in orbit using many lifts of smaller modules, rather than the one shot approach that NASA is employing in developing larger lift capability and the one shot to space approach of the Orion unit. Orion must fit within an envelop needed for launch.

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    $\begingroup$ I'm not sure what your last paragraph has to do with your question. It's also technically wrong. SLS/Orion are built with multiple launch missions in mind. That's why both 1B and 2 blocks include both human rated launch vehicles as well as cargo launch vehicles. Orion on its own, without a capable service module, isn't going much anywhere that we haven't gone before. $\endgroup$
    – TildalWave
    Feb 26, 2015 at 14:44
  • $\begingroup$ Using the same launches required to modify the ISS to instead construct a new spacecraft in orbit would also take advantage of our orbital assembly capabilities, with much better results. There's no reason to equate use of orbital assembly with use of the ISS. Also, just because we possess such capabilities doesn't mean they're a good fit for this particular mission. $\endgroup$ Jun 30, 2018 at 18:59
  • $\begingroup$ You can't place supply repositories in its path - this brings to mind early polar expeditions where they could just stop to pick up the provisions. The supply modules would have to be on a matching trajectory, so you might as well include them from the start. $\endgroup$
    – GordonD
    Feb 14 at 9:58

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The ISS is not designed for the kind of high thrust to escape Earth orbit, nor the duration of time it would take.

The ISS is not designed to operate far from Earth, as it requires constant resupply. If we have trouble resupplying it in low earth orbit, how hard will it be on the way to Mars, and then in Mars orbit? That is a lot of supplies, which currently are provided by 3-4 Progress, 3-4 Dragon, 1-2 Cygnus, maybe an HTV or ATV launch a year. That is a reasonably large amount of payload, that would be very expensive and hard to send on to Mars.

The medical facilities on the ISS depend on return to Earth being available within a day.

As Mark Adler notes, the ISS design is carefully tuned for the thermal environment of low-Earth orbit. It would not work at Mars. The Earth is quite 'warm' compared to space, and Mars is not quite as warm. Solar influx at Mars would be lower than at Earth due to distance from the Sun.

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    $\begingroup$ Also the ISS design is carefully tuned for the thermal environment of low-Earth orbit. It would not work at Mars. $\endgroup$
    – Mark Adler
    Feb 26, 2015 at 16:16
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    $\begingroup$ Technically speaking.... with enough fuel, you could eventually get the ISS to Mars. Not sure if ISS actually would be able to hold all that fuel, but a series of perigee burns would eventually do the job. Of course, it would most likely cease to be a functioning space station, but strictly speaking, it is possible. $\endgroup$
    – Tristan
    Feb 26, 2015 at 21:36
  • $\begingroup$ None of the critical systems would survive transfer through Van Allen belts and beyond. Radiation would likely cook the whole thing fast. And thermals would kill it too. $\endgroup$
    – kert
    Oct 5, 2017 at 4:43
  • $\begingroup$ "...the kind of high thrust to escape Earth orbit..." so use thrust! space.stackexchange.com/search?q=%5Biss%5D+ion $\endgroup$
    – uhoh
    Feb 13 at 23:09
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Yes, you can but like it was said it would need some changes.

  • Better insulation. You would need to keep the internal temperature the same receiving only 43% the solar heat ((149km/228km)²=0,43).

  • Bigger solar panels. 232% the size from earth ones to achieve equivalent power.

  • A bigger fuel tank, with 1 to 4 times the current ISS weight added as fuel (depending on $I_{SP}$ and how long the trip will take.) A simple Hoffman transfer orbit (the bare minimum) needs 2,9km/s, with hydrogen/oxygen fuel (the best traditional fuel) and the ISS would need to add 90,4% of its weight as fuel with no margin for error or losses.
  • Acceleration. With small acceleration you could avoid the structural problems but you would also need to add fuel to compensate for a non-optimal burn. I believe a 0,01G acceleration would be 10 times less than the ISS should be able to handle with retracted solar panels. (So the initial boost would take about 3 hours and 6 hours on Mars.)
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    $\begingroup$ The thermal problem with human occupied spacecraft is getting rid of heat, not keeping them warm. There is no insulation on the ISS to keep it warm and it certainly doesn't need any more. Vacuum is the best insulator around and there's plenty of that in space. $\endgroup$ Oct 2, 2017 at 22:34
  • $\begingroup$ These aren't nearly enough. Radiation environment is completely different, none of the systems would survive the trip $\endgroup$
    – kert
    Oct 5, 2017 at 4:45
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Yes. If you added a slow ion thruster you could slowly raise the orbit, also you can use the moon to help pull you out of the current low earth orbit. Eventually gravity assist passed the moon and on to Mars where you'll need to enter orbit.

Things you'll need:

  1. A large amount of fuel (at least 400 tons (Mangela)), storage, and an ion thruster for the ISS.
  2. Significantly increased radiation shielding for ISS, since it was built for LEO which is well shielded by Earth's magnetic field.
  3. 232% more solar panels, (Mangela).
  4. Regular resupply from earth, though if you start redesigning you can find ways to reduce those needs. (Stable long term orbit without need for regular orbit boosts, food production, simple manufacture with 3D printing for parts, etc.)

So it would be very costly but not impossible. Honestly leaving it in LEO and letting private industry get a crack at using it makes more sense, or only boosting it to lunar orbit with some of the above upgrades. The single shot or Orion style would be cheaper than the large number of launches and assembly that ISS took.

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FWIW, escape velocity from the orbit of ISS is almost the same as Earth's surface, 24,258 mph (10.844 km/s) for ISS as opposed to 25,022 (11.186 km/s) at Earth's mean radius.

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    $\begingroup$ Not that I am endorsing this concept in any way, but isn't the ISS already going 17,130 mph? $\endgroup$ Oct 3, 2017 at 19:18
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    $\begingroup$ Scape velocity is 11km/s and orbital speed 8km/s (routhly) a hofmaffman transfer orbit needs 3km/s at least to mars that means at least 400 tons of fuel for current ISS configuration. $\endgroup$ Oct 3, 2017 at 19:29
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    $\begingroup$ it's Hohmann transfer, btw. $\endgroup$
    – Hobbes
    Oct 3, 2017 at 19:37
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    $\begingroup$ Good comments. For some reason I stupidly ignored ISS's initial velocity and have edited my response accordingly. I'd delete it, but the comments are worth keeping. $\endgroup$
    – BillDOe
    Oct 4, 2017 at 18:09

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