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Alan_Smithee_ t1_jc7kdr7 wrote

Why can’t they just use a Cygnus to do it?

Personally, I’d prefer that they leave it up, and perhaps let private space companies operate it if NASA and partners won’t.

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rocketmonkee t1_jc7spqi wrote

> Why can’t they just use a Cygnus to do it?

Basically, that is what the Request for Information (RFI) is asking. NASA is proposing the idea to use natural orbital decay or propulsion from the Russian Segment, then use the "space tug" to take over for the final de-orbit burn, plus any attitude and Delta-V adjustments during the final de-orbit events.

This announcement is NASA's mechanism to ask the aerospace industry what it thinks, and for the aerospace industry to give ideas.

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Pharisaeus t1_jc7sg48 wrote

> Why can’t they just use a Cygnus to do it?

To small. You'd need something like fully loaded ESA ATV to deliver enough delta-v. Single biggest push ISS ever got was from https://en.wikipedia.org/wiki/Johannes_Kepler_ATV and with 4.5t of fuel (total theoretical payload capacity was 7.5t, but part of that was fuel for ISS, water and dry cargo allocation) it delivered less than 30m/s delta-v, raising orbit form 350 to 400km. Here you need about 50% more. So theoretically fully loaded with fuel it could make it. But that was the biggest resupply craft flying to the ISS.

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