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The Cygnus OA-9 mission has had plenty of extra fuel to burn!

While docked at the ISS, it burned for a while to raise the ISS' orbit. This may have been more of a demonstration and token altitude gain and not a dramatic maneuver, but after receiving a load of trash, it departed the ISS and raised its own altitude to about 500 km in order to deploy several cubesats at that altitude.

It will then have to de-orbit from 500 km all the way into the atmosphere in order to incinerate it's remaining "payload".

Is this a typical amount of "extra" delta-v available to every Cygnus trip to the ISS, or did they do anything special to give it more delta-v than normal, like under-loading its cargo to the ISS or adding extra propulsion during launch?

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  • $\begingroup$ Antares rocket and Signus continue to evolve nasaspaceflight.com/2018/06/…. There are many plans for different flexible designs of Sygnus missions. For OA-9 most probably some enlarged propellant tanks. $\endgroup$ – Heopps Jul 16 '18 at 14:48
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It seems to me that they realized that the spacecraft had far more delta-v then was required, and that they did have enough power to do station change missions. Source.

“We actually started engaging NASA on this topic in the fall of last year,” said Mr. DeMauro. “We have a large engine on the back of the spacecraft that puts out a lot more thrust [than the 32 maneuvering thrusters on Cygnus], and this is the engine we use for orbit raising burns.

“And so we started talking with NASA at the program office about the possibility of Cygnus providing some form of orbit raising capability using that engine. And one of the things we decided to do earlier this year is to put this Detailed Test Objective in place and at least work through the process of seeing if we could get that approved by NASA and of course specifically the safety review panel.”

Of some note is that this is only the third mission with the Antares 230 (Antares Launch History), which has more power then the previous iterations. Likely they had a bit of spare capacity as a result.

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