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#100
by
ChrisGebhardt
on 31 Jan, 2017 15:15
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I thought launch windows to the ISS and LEO were instant
It believe it will be. My understanding is they initially set a short window that is refined closer to launch. I don't know the specifics but it is related to external influences to the ISS' orbit like drag which I guess can vary quite a bit over time.
As it was for Shuttle, too, and all previous SpaceX missions to ISS. Set a window and refine down to the second as you get closer. This is all standard procedure.
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#101
by
IanThePineapple
on 31 Jan, 2017 15:41
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So if they launch 5 seconds late for whatever weird reason, they can still make it?
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#102
by
cscott
on 31 Jan, 2017 15:50
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So if they launch 5 seconds late for whatever weird reason, they can still make it?
AIUI, no. The launch program will be fixed to the instantaneous window, once its position within the current five second window is known.
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#103
by
abaddon
on 31 Jan, 2017 16:47
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So if they launch 5 seconds late for whatever weird reason, they can still make it?
AIUI, no. The launch program will be fixed to the instantaneous window, once its position within the current five second window is known.
Dragon has a surplus of maneuvering fuel and has the ability to be manually commanded, although how much I have no idea, or how much deltaV would be required from five extra seconds of rotation. Obviously there's no reason to actually launch late and they would just scrub and go on to the next opportunity.
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#104
by
ChrisGebhardt
on 31 Jan, 2017 17:12
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So if they launch 5 seconds late for whatever weird reason, they can still make it?
AIUI, no. The launch program will be fixed to the instantaneous window, once its position within the current five second window is known.
Dragon has a surplus of maneuvering fuel and has the ability to be manually commanded, although how much I have no idea, or how much deltaV would be required from five extra seconds of rotation. Obviously there's no reason to actually launch late and they would just scrub and go on to the next opportunity.
It has nothing to do with Dragon's maneuvrability once in orbit and everything to do with hold capability for Falcon 9 launch countdown. A hold after terminal count begins results in a recycle to T-13mins -- and therefore blows the window. Shuttle had the ability to hold at points inside terminal count, which made it different and more flexible in that regard.
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#105
by
abaddon
on 31 Jan, 2017 17:47
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It has nothing to do with Dragon's maneuvrability once in orbit and everything to do with hold capability for Falcon 9 launch countdown. A hold after terminal count begins results in a recycle to T-13mins -- and therefore blows the window. Shuttle had the ability to hold at points inside terminal count, which made it different and more flexible in that regard.
That wasn't the question. The question was if it launched five seconds late "for whatever weird reason", meaning
not holding. Since the Falcon 9 would in such a hypothetical (and unrealistic) scenario follow the pre-programmed trajectory, the ability (or not) of the Dragon to rendezvous with the ISS would have everything to do with the Dragon's maneuverability once on orbit.
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#106
by
Jim
on 31 Jan, 2017 18:06
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Dragon has a surplus of maneuvering fuel and has the ability to be manually commanded, although how much I have no idea, or how much deltaV would be required from five extra seconds of rotation. Obviously there's no reason to actually launch late and they would just scrub and go on to the next opportunity.
Not enough to over come the inclination difference.
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#107
by
ChrisGebhardt
on 31 Jan, 2017 18:07
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It has nothing to do with Dragon's maneuvrability once in orbit and everything to do with hold capability for Falcon 9 launch countdown. A hold after terminal count begins results in a recycle to T-13mins -- and therefore blows the window. Shuttle had the ability to hold at points inside terminal count, which made it different and more flexible in that regard.
That wasn't the question. The question was if it launched five seconds late "for whatever weird reason", meaning not holding. Since the Falcon 9 would in such a hypothetical (and unrealistic) scenario follow the pre-programmed trajectory, the ability (or not) of the Dragon to rendezvous with the ISS would have everything to do with the Dragon's maneuverability once on orbit.
Well, since they
can't launch 5 seconds late as the window is instantaneous, the question is moot for the CRS10/SpX-10 Dragon update thread and should be moved to/asked in general Dragon discussion thread.
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#108
by
Comga
on 31 Jan, 2017 18:09
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It has nothing to do with Dragon's maneuvrability once in orbit and everything to do with hold capability for Falcon 9 launch countdown. A hold after terminal count begins results in a recycle to T-13mins -- and therefore blows the window. Shuttle had the ability to hold at points inside terminal count, which made it different and more flexible in that regard.
That wasn't the question. The question was if it launched five seconds late "for whatever weird reason", meaning not holding. Since the Falcon 9 would in such a hypothetical (and unrealistic) scenario follow the pre-programmed trajectory, the ability (or not) of the Dragon to rendezvous with the ISS would have everything to do with the Dragon's maneuverability once on orbit.
Numerically, a 5 second delay requires a plane change burn of just over 2 meters per second, depending on the altitude at which that maneuver is performed.
A Dragon has much more delta-V available than this.
The fact that there are no credible circumstances under which this would be done doesn't affect the physics.
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#109
by
pechisbeque
on 31 Jan, 2017 18:27
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Dragon has a surplus of maneuvering fuel and has the ability to be manually commanded, although how much I have no idea, or how much deltaV would be required from five extra seconds of rotation. Obviously there's no reason to actually launch late and they would just scrub and go on to the next opportunity.
Not enough to over come the inclination difference.
Wouldn't it be RAAN difference if they kept the same launch azimuth?
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#110
by
stcks
on 31 Jan, 2017 18:52
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Not enough to over come the inclination difference.
Wrong ....
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#111
by
Jim
on 31 Jan, 2017 18:53
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Wouldn't it be RAAN difference if they kept the same launch azimuth?
Correct, I was thinking of yaw steering capability (wrong dog leg).
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#112
by
Senex
on 31 Jan, 2017 19:42
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I nominate stcks for the T-shirt . . .
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#113
by
stcks
on 31 Jan, 2017 20:06
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I nominate stcks for the T-shirt . . .
Being relatively new here, I haven't the foggiest idea what is on this t-shirt. But whatever it is, I'll wear it proudly if it subtly trolls Jim (only out of love of course).
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#114
by
Comga
on 04 Feb, 2017 01:11
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Cross-posting from the Viewing thread. A PM of a rumor doesn't seem enough for the Updates thread.
PM for one of the GSFC / STP-H5 experiments here. We're hearing rumors of a CRS-10 slip to 2/17/17 due to Pad39a preparations. Anyone else hearing this? No information online anywhere; everything still showing 2/14/17. We've got a ton of GSFC engineers & their families traveling down for launch. Everyone is booking travel and looking for the most up-to-date intel on a launch date.
As of right now the Launch is still occurring on 2/14/17. We have seen no evidence of a delay. Chris is always good about releasing slips to the public quickly because of people's travels plans and such. So as soon as he hears different, we will know.
This supposed delay goes against the enthusiasm for the 2/8 and 2.14 dates above and in L2, so it's very much in doubt in my mind.
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#115
by
mainmind
on 04 Feb, 2017 20:45
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#116
by
Herb Schaltegger
on 04 Feb, 2017 20:54
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#117
by
docmordrid
on 04 Feb, 2017 20:59
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Do they even need FAA approval for a NASA or DoD launch? Seems the purchasing agency would do the permitting?
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#118
by
Herb Schaltegger
on 04 Feb, 2017 21:21
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#119
by
joek
on 04 Feb, 2017 21:50
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Do they even need FAA approval for a NASA or DoD launch? Seems the purchasing agency would do the permitting?
In this case, yes. If it is a USG launch (non-commercial) the provider does not need an FAA license; the acquiring agency (e.g., USAF/DoD or NASA) covers it. If it is a commercial launch the provider requires an FAA license. All CRS flights are considered commercial (that is tied to FAR acquisition), therefore an FAA launch license is required by the provider (SpaceX, Orbital, whoever). In short, whether an FAA license is required it tied to how the launch services were acquired.
