Man, that is big piece of hardware that came off....
Wowo! What the heck is that? What is happening?
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
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..
Quote from: litton4 on 09/04/2023 02:21 pmI'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
I wish I could fully capture how stunning the view from the Cupola is. It’s not just the view of Earth that amazes me, but also looking at this incredible orbiting laboratory we’ve constructed in space. @Space_Station is a testament to what humans can do when we work together.
260623Z JAN 24NAVAREA 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.