Author Topic: SpaceX F9 / Crew Dragon : Crew-7 : KSC LC-39A : 26 August 2023 (07:27 UTC)  (Read 127922 times)

Online FutureSpaceTourist

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More NASA Crew-7 arrival photos from flickr

Online kdhilliard

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Man, that is big piece of hardware that came off.
...
Reformatted links:
20-second short "dragon crew 7 fod": https://youtube.com/watch?v=D3OdOhohjVA
Timestamped link to source video: https://youtube.com/watch?v=5KeIAYTW8eQ&t=4888
Wowo! What the heck is that? What is happening?
*One* thing happening is the forum breaking the time stamp for embedded video.
A workaround is using the long-form links but removing the "www." to suppress embedding, as I've done above.
Note that the second video starts with the opening of the nosecone at 1:21:28, and the not-so-captive nutplate makes its appearance 74 seconds later at 1:22:42.

Online LouScheffer

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Here's a hand-wavey argument to show the very short re-entry burn was likely plausible and deliberate.

First, note that RTLS entries with a long (20 second-ish) re-entry burn then have very low aerodynamic deceleration thereafter (about 2G).

Next, note that Starlink ASDS re-entry burns exit at a much higher velocity, and hence have a much higher atmospheric deceleration (about 6Gs)

Finally the two missions shown in the first example above shows a clear tradeoff.  With an entry burn about 2 seconds shorter, the peak atmospheric deceleration is higher by about 0.3G.   If this tradeoff continues (plausible as the widths of the two spikes are similar, and the sum of the area under the two curves must be the same) then a 20 second reduction in entry burn would result in about 3Gs more aero deceleration, or very roughly 5Gs total.  But we know from the Starlink missions (second example above) that the booster can withstand about 6G aero deceleration without eating into its lifetime.  And a 20 second reduction in the re-entry burn brings us to about 3 seconds, as observed.

Of course this is an oversimplification, as the RTLS is coming almost straight down whereas the ASDS missions still have a large horizontal component even after the entry burn.  This means the RLTS mission will hit the denser atmosphere more quickly than ASDS entries, which may result in less total deceleration from similar peak deceleration. But it's very clear, however, that a much shorter entry burn will be allowed before the booster reaches the demonstrated 6G aero deceleration limit.

P.S.  In retrospect, SpaceX has clearly been working up tp this.  Here is transporter 7, with an 11 second, one engine, re-entry burn, followed by a 5G aero decleration.  This gave a very significant 163 m/s performance boost compared to Transporter-6, which used a classic 20 second re-entry burn.  And an even shorter but 3-engine burn should be even more efficient.  Plus there is still some margin to get to the 6G aero deceleration shown in the ASDS entries.
« Last Edit: 08/31/2023 06:35 pm by LouScheffer »

Offline shiro

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Some reusability stats for this launch (SpaceX Crew-7):

Booster B1081.1 turnaround time: N/A
(the booster is brand new).

FYI: median turnaround time for Falcon 9 / Heavy boosters is currently 53.69 days *
* based on the last 30 launches, excluding new first stages.

Launchpad LC-39A turnaround time: 29 days 4 hours 23 minutes
(the previous launch from this pad was Falcon Heavy with Jupiter-3 (EchoStar-24) on Jul 29, 2023).

FYI: median turnaround time for LC-39A is currently 15.64 days *
* based on the last 30 launches.

The same type of stats for previous SpaceX launches may be found on this spreadsheet online.

Online FutureSpaceTourist

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Nice Crew-7 video montage on this tweet:

https://twitter.com/spacex/status/1698171421418263012

Quote
One week after @NASA's Crew-7 arrived at the @space_station, Dragon and the Crew-6 astronauts are set to depart on Sunday, September 3 → spacex.com/launches
« Last Edit: 09/03/2023 05:12 am by FutureSpaceTourist »

Offline litton4

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Here's a hand-wavey argument to show the very short re-entry burn was likely plausible and deliberate.

First, note that RTLS entries with a long (20 second-ish) re-entry burn then have very low aerodynamic deceleration thereafter (about 2G).

Next, note that Starlink ASDS re-entry burns exit at a much higher velocity, and hence have a much higher atmospheric deceleration (about 6Gs)

Finally the two missions shown in the first example above shows a clear tradeoff.  With an entry burn about 2 seconds shorter, the peak atmospheric deceleration is higher by about 0.3G.   If this tradeoff continues (plausible as the widths of the two spikes are similar, and the sum of the area under the two curves must be the same) then a 20 second reduction in entry burn would result in about 3Gs more aero deceleration, or very roughly 5Gs total.  But we know from the Starlink missions (second example above) that the booster can withstand about 6G aero deceleration without eating into its lifetime.  And a 20 second reduction in the re-entry burn brings us to about 3 seconds, as observed.

Of course this is an oversimplification, as the RTLS is coming almost straight down whereas the ASDS missions still have a large horizontal component even after the entry burn.  This means the RLTS mission will hit the denser atmosphere more quickly than ASDS entries, which may result in less total deceleration from similar peak deceleration. But it's very clear, however, that a much shorter entry burn will be allowed before the booster reaches the demonstrated 6G aero deceleration limit.

P.S.  In retrospect, SpaceX has clearly been working up tp this.  Here is transporter 7, with an 11 second, one engine, re-entry burn, followed by a 5G aero decleration.  This gave a very significant 163 m/s performance boost compared to Transporter-6, which used a classic 20 second re-entry burn.  And an even shorter but 3-engine burn should be even more efficient.  Plus there is still some margin to get to the 6G aero deceleration shown in the ASDS entries.

I've also noticed that they don't provide the telemetry for the booster after second stage sep on crew missions, like they do on Starlink ones (at least on Crew 6 and 7), which means none of the informative plots that our esteemed member @OneSpeed has often provided, thus denying much analysis..
« Last Edit: 09/04/2023 02:31 pm by litton4 »
Dave Condliffe

Offline OneSpeed

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I've also noticed that they don't provide the telemetry for the booster after second stage sep on crew missions, like they do on Starlink ones (at least on Crew 6 and 7), which means none of the informative plots that our esteemed member @OneSpeed has often provided, thus denying much analysis..

I've had my best shot at it here: https://forum.nasaspaceflight.com/index.php?topic=42389.msg2520990#msg2520990

Offline litton4

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I've also noticed that they don't provide the telemetry for the booster after second stage sep on crew missions, like they do on Starlink ones (at least on Crew 6 and 7), which means none of the informative plots that our esteemed member @OneSpeed has often provided, thus denying much analysis..

I've had my best shot at it here: https://forum.nasaspaceflight.com/index.php?topic=42389.msg2520990#msg2520990

Fantastic! Thanks!
Dave Condliffe

Online FutureSpaceTourist

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https://twitter.com/astrojaws/status/1700174701232882110

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I wish I could fully capture how stunning the view from the Cupola is. Its not just the view of Earth that amazes me, but also looking at this incredible orbiting laboratory weve constructed in space. @Space_Station  is a testament to what humans can do when we work together.

Online FutureSpaceTourist

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Some launch day photos from NASA Kennedy flickr that I dont think have been posted before

Online Oersted

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Got to say I am somewhat disappointed about how very little we hear from Crew-7 in the media. There was so much talk in Denmark about Andreas Mogensen before his long-duration mission, but since he went up... Well, basically very little has been heard from him. He did put a Danish flag in the Cupola for the recent Danish succession of the throne. But apart from that, not much. At least not that hit mainstream media...

Online Oersted

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Crew-7 just got a date for their return: 'no earlier than March 8'.

Tweet by Commander Mogensen:
https://twitter.com/Astro_Andreas/status/1758434989723504958

No spacewalk for him.
« Last Edit: 02/16/2024 09:20 pm by Oersted »

Offline Ken the Bin

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NGA Space Debris notice that appears to be a splashdown notice for Crew-7, but way early. I can't think of anything else expected to return before Crew-7.

Quote from: NGA
260623Z JAN 24
NAVAREA IV 190/24(11).
GULF OF MEXICO.
WESTERN NORTH ATLANTIC.
FLORIDA.
1. HAZARDOUS OPERATIONS, SPACE DEBRIS
   A. 251520Z TO 251550Z FEB, ALTERNATE
      260630Z FEB TO 031305Z MAR
      IN AREA WITHIN NINE MILES OF
      28-50.99N 080-13.80W.
   B. 251520Z TO 251550Z FEB, ALTERNATE
      260640Z FEB TO 031305Z MAR
      IN AREA WITHIN NINE MILES OF
      29-47.99N 080-40.01W.
   C. 251510Z TO 251540Z FEB, ALTERNATE
      260640Z FEB TO 031300Z MAR
      IN AREA WITHIN NINE MILES OF
      30-54.84N 080-15.00W.
   D. 250725Z TO 250755Z FEB, ALTERNATE
      251540Z FEB TO 031325Z MAR
      IN AREA WITHIN NINE MILES OF
      29-42.85N 086-10.86W.
   E. 250730Z TO 250800Z FEB, ALTERNATE
      251545Z FEB TO 031330Z MAR
      IN AREA WITHIN NINE MILES OF
      29-47.99N 087-30.00W.
   F. 250715Z TO 250745Z FEB, ALTERNATE
      251535Z FEB TO 031320Z MAR
      IN AREA WITHIN NINE MILES OF
      29-16.55N 084-12.00W.
   G. 251540Z TO 251610Z FEB, ALTERNATE
      260645Z FEB TO 031325Z MAR
      IN AREA WITHIN NINE MILES OF
      28-05.99N 083-54.00W.
2. CANCEL THIS MSG 031430Z MAR 24.

Online FutureSpaceTourist

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https://twitter.com/cknasaboy/status/1763704351611056462

Quote
Crew Dragon Endurance, lit by the rising moon, with star trails and Earth-glow in the background - this is a 150 second, f11, ISO 1000 exposure.

Not pictured - the 10 blurry horrible messes before I snagged this one lol

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