# Could the Crew Dragon be used to re-boost the ISS?

In an answer to a related question, Jörg W Mittag wrote the following:

But more importantly, handling of the Superdracos is currently rather simple. They are safed after reaching orbit and then never turned on again. This means that there is no possible way in which they could accidentally fire in the vicinity of the ISS, for example, or during recovery operations. Otherwise, all of that would have to be certified, too. (The ISS guys are understandably very peculiar about what can be fired with how much thrust in which direction while in the vicinity of their station.)

Now I can't stop thinking about using the SuperDracos to reboost the ISS. Given that there's this chunk of delta-v aboard the Crew Dragon that costs good money to be carried all the way to orbit, it'd be great if one could put it to a good use once launch escape is no longer a concern.

Alternatively, could the small Draco thrusters be used instead? They do have a higher Isp (300 s) than the SuperDracos (235 s), but they would have to burn for minutes to make a difference for the entire 400-ton ISS.

I assume that there are currently no plans for that, with the likely reason being that certifying the Crew Dragon for ISS reboosts would be too expensive. However, it still feels nice to use this free delta-v somehow, thus freeing up some upmass capacity on the cargo resupply flights. Also, having a backup reboost mechanism feels useful as well.

Certification costs aside, would it be possible to use the Crew Dragon to re-boost the ISS, without requiring a massive redesign of the capsule, the docking mechanism, or the ISS? (Of course some flight software development for the Dragon is unavoidable.)

• Delta-v wise it works out to 7.48m/s when the Crew Dragon were to be fully fueled. mass of crew Dragon is 8.9tons. Fuel capacity 1388kg when full. Isp is 235s. Mass of the ISS is 419,700kg, give or take. $\Delta v = 235s \cdot g_0 \cdot ln(\frac{419.7 + 8.9}{419.7 + 8.9 - 1.388}) = 7.48m/s$, so it definitely has enough punch, most re-boosts I could found were in the ballpark of 1.5m/s. – Polygnome Aug 4 '20 at 13:10
• I'd be a bit surprised if the Dragon's main thrust vector is anywhere near the ISS's center of mass, meaning that it would be difficult to avoid imparting spin – Carl Witthoft Aug 5 '20 at 12:13