Starliner's abort engines, like Crew Dragon's SuperDracos, are for aborts only. Not sure if there's any configuration to allow a throttled use of either for non-abort use.
Quote from: MattMason on 08/07/2021 07:31 pmStarliner's abort engines, like Crew Dragon's SuperDracos, are for aborts only. Not sure if there's any configuration to allow a throttled use of either for non-abort use.No certified configuration. Though in all seriousness, even though the SuperDracos can be throttled relatively well (they were designed for powered landing, after all), the minimum power level is still probably far above what anybody would want to use in pushing the ISS around. That is a task that requires gentle pushes, not heavy slams.
It has to be kept clear that the concept is for Cargo Dragon to boost the ISS, presumably in the absence of the Russians. Cargo Dragon has no Super Dracos.We can take gongora’s post as certain, that Crew Dragon is not going to be used for Station orbit maintenance or debris avoidance maneuvers. We can agree with rpapo that there is no certified configuration for this. We can agree with MattMason that it “may not be needed” but organizations prepare for all sorts of contingencies that are only possibilities. So the point would be to think of the more probable configurations and see if NASA ever makes public anything like them. IMHO if I remember correctly, the upcoming Dream Chaser cargo vessel from Sierra Nevada has or will have a reboost capability, may require additional hardware resources they are developing, se the "Shooting Star Transport Vehicle"
Wonder if it has been looked at for cargo Dragons?
Cygnus is getting updated for station boosting.https://forum.nasaspaceflight.com/index.php?topic=21179.msg2274831#msg2274831
Quote from: darkenfast on 08/10/2021 10:08 amCygnus is getting updated for station boosting.https://forum.nasaspaceflight.com/index.php?topic=21179.msg2274831#msg2274831I assume NGIS did this upgrade at NASA's request. Unless there is financial incentive or relibility issue why modify such reliable vehicle.Sent from my SM-G570Y using Tapatalk
By now boost servicing shouldn't even be necessary. The station should have been outfitted with electric thrusters and requisite power sources ages ago.
Meanwhile the Chinese station has electric propulsion systems flying and operational.
Maybe to test out systems for the HALO module for the Lunar Gateway mention in the tweet by Marcia Smith.
C. Electric thrusters would ruin the micro gravity environment negating the major reason the ISS exists
Quote from: Jim on 08/11/2021 01:04 pmC. Electric thrusters would ruin the micro gravity environment negating the major reason the ISS existsI've always been bothered by that stance, since atmospheric drag by definition is messing with the microgravity environment onboard ISS.Is the claim that continuous variable small thrust by electric propulsion counteracting drag in realtime isn't feasible leading to the thinking that you would then have to have continuous electric thrust at the average drag rate, thus leading to random undesired movement due to imbalance between constant thrust and instantaneous air drag ruining the microgravity environment? I'm having trouble reconciling that with how that would that be qualitatively worse than random air drag also messing with the microgravity environment?