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#860
by
Comga
on 02 Mar, 2019 14:40
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Why barge and not land landing for the first stage?
I thought it would have enough performance for coming back to cape canaveral on this kind of payload.
This kind of payload? What do you expect with a +12 metric ton spacecraft on top of the rocket? This is the heaviest thing a Falcon 9 has ever launched to ANY orbit. Add that to the "reserving performance" thing and inevitably they have to land on the droneship.
Is there not also a belief that the S1 trajectory was lower than usual, so any boostback burn would have to add height as well, increasing propellant requirements?
It seems it might have been all a misunderstanding, it was actually a lofted trajectory and in some way even more lofted that some cargo missions. I don't understand very well how NASA would like such trajectory, if Falcon 9 has a bad day and the crew has to abort mid-flight, they will have quite a hard reentry with all the g-forces. Soyuz usually flies a flat trajectory, they usually take about the same time to get to a similar orbit as this Dragon has gone into but if you look back at their failure in October the rocket was still about 50km up at about 2 minutes or so and the apogee after abort never went higher than 100km and the rocket was travelling almost horizontal from the external camera views (not exactly horizontal, but you know, something like 30º or something like that, maybe even less than that). If only this flight could have been in daylight to have some visual reference... but all we have is the telemetry from the webcast. Maybe we could even compare that with the "telemetry" from Roscosmos coverage of the Soyuz launches but I'm not sure about how an abort would be better with a lofted trajectory...
This has been discussed MANY times up-thread.
I believe you have this backwards.
It is a flatter trajectory, the opposite of lofted
That makes it easier to understand why the ASDS is so far downrange.
You could look in the L2 Simulations thread and probably find just what you want or ask OneSpeed for a side-by-side.
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#861
by
Comga
on 02 Mar, 2019 14:43
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So stupid question.
Will Dragon2 take this long to reach the ISS when there are crew on board as well?
If so, how do they “go to the toilet” during that roughly 24 hour period?
Not a stupid question but one directly answered yesterday.
It will take less time for operational flights.
Sanitary needs have been discussed. This is not new and still an issue for even the shortest times to docking.
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#862
by
MattMason
on 02 Mar, 2019 14:43
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So stupid question.
Will Dragon2 take this long to reach the ISS when there are crew on board as well? If so, how do they “go to the toilet” during that roughly 24 hour period?
According to this Business Insider article, the Crew Dragon is equipped with a toilet and privacy curtain. Given its other posh comforts (for a spacecraft) this isn't surprising to me.
I'm not sure if KSC CC launches could adapt the "fast-track" 6 hour rendezvous method developed by Roscosmos for Soyuz. Doubt it because of the starting inclinations of KSC, while Balkanaur is almost already on that inclination.
https://www.businessinsider.com/spacex-crew-dragon-capsule-what-its-like-inside-2018-8
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#863
by
Comga
on 02 Mar, 2019 14:47
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So stupid question.
Will Dragon2 take this long to reach the ISS when there are crew on board as well? If so, how do they “go to the toilet” during that roughly 24 hour period?
According to this Business Insider article, the Crew Dragon is equipped with a toilet and privacy curtain. Given its other posh comforts (for a spacecraft) this isn't surprising to me.
I'm not sure if KSC CC launches could adapt the "fast-track" 6 hour rendezvous method developed by Roscosmos for Soyuz. Doubt it because of the starting inclinations of KSC, while Balkanaur is almost already on that inclination.
https://www.businessinsider.com/spacex-crew-dragon-capsule-what-its-like-inside-2018-8
No one is going behind a privacy curtain to use the toilet during long stretches before and during the launch, so that's not a total answer.
My understanding is that the fast (3 orbit?) rendezvous opportunities occur on three day cycles and require additional orbit adjustment by the ISS, so they are not preferable from a Station perspective.
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#864
by
M.E.T.
on 02 Mar, 2019 14:51
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Thanks. Will do a search for the relevant thread, as this topic has me intrigued.
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#865
by
Johnnyhinbos
on 02 Mar, 2019 15:02
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I really wish at one of these many press conferences that someone asked if the D2’s will return to Earth with all of its unused hypergolic propellant onboard, or if it dumps it at some point.
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#866
by
M.E.T.
on 02 Mar, 2019 15:10
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I really wish at one of these many press conferences that someone asked if the D2’s will return to Earth with all of its unused hypergolic propellant onboard, or if it dumps it at some point.
Yes, because that touches on another question - often asked but still not 100% clarified in my mind - which is whether Dragon 2’s thrusters can still slow it down for a survivable landing if the parachutes fail.
The previous consensus seemed to be no, due to the software not being programmed for it or something along those lines, but if the fuel is retained then in theory the capability could potentially still be there?
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#867
by
Svetoslav
on 02 Mar, 2019 15:10
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#868
by
lonestriker
on 02 Mar, 2019 15:14
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I really wish at one of these many press conferences that someone asked if the D2’s will return to Earth with all of its unused hypergolic propellant onboard, or if it dumps it at some point.
Being an (software) engineer, I would prefer to keep the super dracos as options all the way till landing. My bet would be that have the old propulsive landing routines buried in their emergency software decision tree as a last resort if the capsule is in free fall after a certain altitude (turned off once the vehicle is safed.) Complete conjecture on my part with no basis in known facts...
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#869
by
JimO
on 02 Mar, 2019 15:20
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Anyone knows how to track SpX-DM1 or how to find out its current orbital parmeters? I'd like to try taking a photo of ISS with a Dragon chasing it up. My understanding is that Dragon should be on similar orbit: with the same inclination, right ascension of the ascending node, just slightly lower apogee and/or perigee to catch up with the ISS.
Are the orbital parameters available anywhere? I'd like to observe it tonight and was wondering how far away from ISS the Dragon will be.
Dragon is in plane with ISS and catching up from behind in a lower orbit with a higher rev rate. If you can see ISS, you should see Dragon chasing it along the same path a few minutes later.
Actually, not exactly. You'll see its path displaced by the distance earth's rotation has carried you in the interval between passes. See
http://www.jamesoberg.com/95sep-feelingorbmechanics.pdf
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#870
by
kevinof
on 02 Mar, 2019 15:36
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Not sure Dragon even has a radar altimeter - doubt it could accurately determine it's height above ground in order to control the thrusters.
As much as many of us would love to see this come down on land, it ain't going to happen.
I really wish at one of these many press conferences that someone asked if the D2’s will return to Earth with all of its unused hypergolic propellant onboard, or if it dumps it at some point.
Being an (software) engineer, I would prefer to keep the super dracos as options all the way till landing. My bet would be that have the old propulsive landing routines buried in their emergency software decision tree as a last resort if the capsule is in free fall after a certain altitude (turned off once the vehicle is safed.) Complete conjecture on my part with no basis in known facts...
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#871
by
envy887
on 02 Mar, 2019 15:42
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Anyone knows how to track SpX-DM1 or how to find out its current orbital parmeters? I'd like to try taking a photo of ISS with a Dragon chasing it up. My understanding is that Dragon should be on similar orbit: with the same inclination, right ascension of the ascending node, just slightly lower apogee and/or perigee to catch up with the ISS.
Are the orbital parameters available anywhere? I'd like to observe it tonight and was wondering how far away from ISS the Dragon will be.
Dragon is in plane with ISS and catching up from behind in a lower orbit with a higher rev rate. If you can see ISS, you should see Dragon chasing it along the same path a few minutes later.
Actually, not exactly. You'll see its path displaced by the distance earth's rotation has carried you in the interval between passes. See http://www.jamesoberg.com/95sep-feelingorbmechanics.pdf
Yes, I should say a similar path. Earth's rotation will carry it 20-30 or so km west or every minute it's lagging ISS.
TLEs are now out so that will make it easier to spot. From the update thread:
1 44063U 19011A 19061.53104934 -.19125596 12647+0 -26592-1 0 9999
2 44063 51.6390 171.6721 0109052 53.9126 60.6836 15.92094578 33
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#872
by
Alexphysics
on 02 Mar, 2019 16:05
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Why barge and not land landing for the first stage?
I thought it would have enough performance for coming back to cape canaveral on this kind of payload.
This kind of payload? What do you expect with a +12 metric ton spacecraft on top of the rocket? This is the heaviest thing a Falcon 9 has ever launched to ANY orbit. Add that to the "reserving performance" thing and inevitably they have to land on the droneship.
Is there not also a belief that the S1 trajectory was lower than usual, so any boostback burn would have to add height as well, increasing propellant requirements?
It seems it might have been all a misunderstanding, it was actually a lofted trajectory and in some way even more lofted that some cargo missions. I don't understand very well how NASA would like such trajectory, if Falcon 9 has a bad day and the crew has to abort mid-flight, they will have quite a hard reentry with all the g-forces. Soyuz usually flies a flat trajectory, they usually take about the same time to get to a similar orbit as this Dragon has gone into but if you look back at their failure in October the rocket was still about 50km up at about 2 minutes or so and the apogee after abort never went higher than 100km and the rocket was travelling almost horizontal from the external camera views (not exactly horizontal, but you know, something like 30º or something like that, maybe even less than that). If only this flight could have been in daylight to have some visual reference... but all we have is the telemetry from the webcast. Maybe we could even compare that with the "telemetry" from Roscosmos coverage of the Soyuz launches but I'm not sure about how an abort would be better with a lofted trajectory...
This has been discussed MANY times up-thread.
I believe you have this backwards.
It is a flatter trajectory, the opposite of lofted
That makes it easier to understand why the ASDS is so far downrange.
You could look in the L2 Simulations thread and probably find just what you want or ask OneSpeed for a side-by-side.
Dude, relax for a sec. My comment was not based on what we thought previously but rather about we have seen on the webcast. Just read the numbers on the webcast then come here to rant about my comment and say I'm wrong just because you didn't even compare numbers.
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#873
by
Alexphysics
on 02 Mar, 2019 16:06
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So stupid question.
Will Dragon2 take this long to reach the ISS when there are crew on board as well? If so, how do they “go to the toilet” during that roughly 24 hour period?
If they decide to do it in 24h, they will have more opportunities. For a 6h rendezvous they may have just two or three days a month to do it and for a faster one obviously a less frequency. 24h sounds right for me, it gives you time to take a rest inside Dragon before docking with the ISS. Also the capsule has a toilet, no need to worry about that.
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#874
by
Alexphysics
on 02 Mar, 2019 16:08
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So stupid question.
Will Dragon2 take this long to reach the ISS when there are crew on board as well? If so, how do they “go to the toilet” during that roughly 24 hour period?
According to this Business Insider article, the Crew Dragon is equipped with a toilet and privacy curtain. Given its other posh comforts (for a spacecraft) this isn't surprising to me.
I'm not sure if KSC CC launches could adapt the "fast-track" 6 hour rendezvous method developed by Roscosmos for Soyuz. Doubt it because of the starting inclinations of KSC, while Balkanaur is almost already on that inclination.
https://www.businessinsider.com/spacex-crew-dragon-capsule-what-its-like-inside-2018-8
Inclination is not a real problem unless the launch site is at a higher latitude than 51.66º
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#875
by
Johnnyhinbos
on 02 Mar, 2019 16:09
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So stupid question.
Will Dragon2 take this long to reach the ISS when there are crew on board as well? If so, how do they “go to the toilet” during that roughly 24 hour period?
If they decide to do it in 24h, they will have more opportunities. For a 6h rendezvous they may have just two or three days a month to do it and for a faster one obviously a less frequency. 24h sounds right for me, it gives you time to take a rest inside Dragon before docking with the ISS. Also the capsule has a toilet, no need to worry about that.
I don’t know about that - depends on what you had for breakfast...
Apollo 8
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#876
by
matthewkantar
on 02 Mar, 2019 16:10
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I never noticed up until now that one section of a pipe on an MVac gets red hot during operation. I went back to the Nusantara Satu webcast and it was there as well, it appeared to be a duller red glow, but maybe it's down to the the camera auto exposure.
I saw that too, was sort of scary looking while I was only half awake. Looking at it today on replays, I think it was a kink in the foil at the base of the MVac reflecting the glow of the nozzle. Would like to know for sure.
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#877
by
Alexphysics
on 02 Mar, 2019 16:10
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So stupid question.
Will Dragon2 take this long to reach the ISS when there are crew on board as well? If so, how do they “go to the toilet” during that roughly 24 hour period?
If they decide to do it in 24h, they will have more opportunities. For a 6h rendezvous they may have just two or three days a month to do it and for a faster one obviously a less frequency. 24h sounds right for me, it gives you time to take a rest inside Dragon before docking with the ISS. Also the capsule has a toilet, no need to worry about that.
I don’t know about that - depends on what you had for breakfast...
Apollo 8
Ok... just consider a norminal situation
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#878
by
testguy
on 02 Mar, 2019 16:21
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I wasn't sure where to post this comment but I guess here is as good as any. The interior of the Dragon 2 capsule as you would expect from Musk: is clean, smooth lines, uncluttered, minimalistic yet functional. It appears to have been designed by an auto designer Ha Ha. On the other hand the interior of the ISS is just the opposite and looks like a science experiment, because IT IS a science experiment. That being said I would expect to see the same interior design philosophy of the Dragon 2 being carried over to the Starship. I can't wait to see the first real renderings or hardware in place for the Starship interior. That shouldn't be too much longer.
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#879
by
Jcc
on 02 Mar, 2019 16:22
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So stupid question.
Will Dragon2 take this long to reach the ISS when there are crew on board as well? If so, how do they “go to the toilet” during that roughly 24 hour period?
If they decide to do it in 24h, they will have more opportunities. For a 6h rendezvous they may have just two or three days a month to do it and for a faster one obviously a less frequency. 24h sounds right for me, it gives you time to take a rest inside Dragon before docking with the ISS. Also the capsule has a toilet, no need to worry about that.
I don’t know about that - depends on what you had for breakfast...
Apollo 8
Or, just "Depends"
https://www.depend.com/en-us/
