SpaceX F9 : CRS SpX-19 : December 5, 2019 - DISCUSSION

[gongora]

Was it 20th on that droneship?  I seem to recall seeing that number mentioned before the launch.  (I haven't actually watched the launch with sound turned on yet.)

[Ghoti]

Dragon has flown 20 times and returned.

[su27k]

Don't have time to count, but I assumed he meant 20th booster to be recovered, there were 40 something landings, but some of the boosters landed more than once.

[edkyle99]

So why did the SpaceX commentator say today's booster recovery was the 20th? Per the first two posts of the manifest, there have been over 40.

https://forum.nasaspaceflight.com/index.php?topic=43418.0

20th successful landing and, presumably, full recovery return to port, on OCISLY (out of 27 attempts).  A total of 45 successful landings (and returns to port) have occurred, performed by 27 boosters.  Three boosters (19, 26, and 42) were retired after only one flight, despite landing.

First Stage Landing Stats
as of 12/05/2019
---------------------------------------
Successes/Attempts      45/54*
F9 Successes/Attempts   39/45
FH Successes/Attempts    6/9*
OCISLY                  20/27*
JRTI                     7/8
CC LZ-1                 13/14
CC LZ-2                  3/3
VA LZ-4                  2/2
---------------------------------------
* FH-2 Core B1055.1 landed successfully on OSCILY, but subsequently 
  toppled and was lost.  Is not counted as a success in these numbers.

 - Ed Kyle

[ZachS09]

What are the TLEs for the initial orbit insertion?

[Raul]

What are the TLEs for the initial orbit insertion?

0 DRAGON CRS-19
1 44821U 19083A   19339.74539757 -.00003561  11257-4  00000+0 0  9997
2 44821  51.6416 231.3246 0130257  46.9556  65.0049 15.94162986    03

2019-083A - DRAGON CRS-19 - 2019-12-05 17:53 UTC - 210.91/384.64km/51.64°

[CyndyC]

https://twitter.com/trevormahlmann/status/1202643983207407616

Beautifully clear weather today for #CRS19! Here’s a long exposure I made on my iPhone with the @NightCapApp from the roof of the Vehicle Assembly Building! GO Dragon!

⚙️/⬇️/🖼: tmahlmann.com/photos/Rockets…

I do not recall ever seeing a launch image like this before, it's fascinating.  Is that the exhaust gases falling back down into the atmosphere?  There wouldn't be anything holding them up, so it's clouds gently raining down from the sky.

I suspect it is the contrail that forms around Max-Q, slowly drifting and dispersing in this time-lapse.

 - Ed Kyle

The cascade is not exhaust but indeed condensation, and forms not at Max-Q but instead approaching and reaching the sound barrier. The callout for "supersonic" begins most precisely at T+00:01:03, and the callout for "maximum aerodynamic pressure" begins 11 seconds later, at T+00:01:14. Condensation forms because the air pressure decreases surrounding vehicles approaching and reaching the sound barrier. Then picture squeezing water from a rag lengthwise, which would be analogous to what MaxQ did with the vapor.

In all honesty, I learned of this phenomenon just this past October, when a Jacksonville hobbyist photographer's photo from the Jacksonville Sea and Sky airshow was explained by a local meteorologist. That photo and one other like it were posted publicly on Facebook, so I am sharing both. The plane is the USAF F-35 Lightning, and photo credit to Moody McCall.

The vertical temperature and dew point gradients at the Cape would have also had an impact, so I am including a description of Florida weather typical for this time of year, from meteorologist Matt Devitt at WINK Weather covering SW Florida. 

[jgoldader]

ISS flying into sunset with Dragon trailing behind, from the Philadelphia suburbs a few minutes ago.  My first sight of a Dragon!

[docmordrid]

Any word on the 2nd stage coast/restart experiment?  Will we know anything?

Maybe the experiment is still underway …

 - Ed Kyle

Cross posting from the updates thread,

One more box ticked for US Air Force GEO launches.

Space News...

Falcon 9 cargo mission for NASA demonstrated long-duration coast required by U.S. Air Force

LOS ANGELES  The upper stage of the SpaceX Falcon 9 mission to the International Space Station Dec. 5 successfully performed a six-hour coast and a deorbit burn, a test that had been requested by the U.S. Air Force to demonstrate the vehicle can deliver national security payloads directly to geosynchronous Earth orbit.
>

[northenarc]

 So I noted in this post https://forum.nasaspaceflight.com/index.php?topic=49550.msg2022448#msg2022448
 that SpaceX 'limited stage 2 acceleration to 3.5g'. This sounded familiar to me from I think ULA launches describing a '3.5g throttle segment', and perhaps somewhere else where I'd heard it was desirable for some payloads to limit acceleration to this level. Was this perhaps yet another aspect, along with the stage 2 on orbit, testing to certify Falcon for certain military and intelligence payloads? Or nothing to do with anything.   

[ZachS09]

So I noted in this post https://forum.nasaspaceflight.com/index.php?topic=49550.msg2022448#msg2022448
 that SpaceX 'limited stage 2 acceleration to 3.5g'. This sounded familiar to me from I think ULA launches describing a '3.5g throttle segment', and perhaps somewhere else where I'd heard it was desirable for some payloads to limit acceleration to this level. Was this perhaps yet another aspect, along with the stage 2 on orbit, testing to certify Falcon for certain military and intelligence payloads? Or nothing to do with anything.   

ULA mentioned the “3.5g throttling” because they have to keep the Atlas V’s RD-180 and RL-10 engines at a level to maintain that acceleration for crew reasons. Keeping true to the typically-used throttle profile could cause the crew to black-out.

[hoku]

So I noted in this post https://forum.nasaspaceflight.com/index.php?topic=49550.msg2022448#msg2022448
 that SpaceX 'limited stage 2 acceleration to 3.5g'. This sounded familiar to me from I think ULA launches describing a '3.5g throttle segment', and perhaps somewhere else where I'd heard it was desirable for some payloads to limit acceleration to this level. Was this perhaps yet another aspect, along with the stage 2 on orbit, testing to certify Falcon for certain military and intelligence payloads? Or nothing to do with anything.

EELV (and presumably also NSSL) Standard Interface Specifications (SIS) for, e.g., a payload mass of 6000 lb limit the "vertical" acceleration to 3.5 g in case the lateral acceleration might exceed 0.5 g.

The interface specs are indeed most likely derived from the military and intelligence payload requirements, like, e.g., Orion-type SIGINT satellites, which might have light-weight "fragile" deployable radio antennas with densities of at most 0.5 kg per square meter (0.1 lb / sq ft).

[Comga]

Cargo.

Curious illustration
From NASA?
Is that the Starliner “trunk”?

[gongora]

Curious illustration
From NASA?
Is that the Starliner “trunk”?

That's the Dragon trunk.

[haywoodfloyd]

I noticed yesterday when they brought OCISLY back with CRS19 that the first stage looked like it was leaning slightly.
Is that a problem with the hydraulics in the landing legs?
It's not a very big lean just curious.

[Mike_1179]

I noticed yesterday when they brought OCISLY back with CRS19 that the first stage looked like it was leaning slightly.
Is that a problem with the hydraulics in the landing legs?
It's not a very big lean just curious.

Don’t think it was anything out of ordinary, but there is a crush-core in each leg at the end is the travel for the piston. This absorbs some landing impact. If it comes in off vertical, that first leg to touch can take a larger load and would use up more of the crush/core.

Don’t know if it really is leaning or is that an artifact of wide-angle lenses, but even if it were, there are benign explanations

[Comga]

Curious illustration
From NASA?
Is that the Starliner “trunk”?

That's the Dragon trunk.

No it’s not.
It has narrow external pods in threefold symmetry, no solar panels, and some small protuberance.

[Gliderflyer]

Curious illustration
From NASA?
Is that the Starliner “trunk”?

That's the Dragon trunk.

No it’s not.
It has narrow external pods in threefold symmetry, no solar panels, and some small protuberance.

Pretty sure its Dragon. It has some weird perspective going on with the solar array covers.

[Comga]

Curious illustration
From NASA?
Is that the Starliner “trunk”?

That's the Dragon trunk.

No it’s not.
It has narrow external pods in threefold symmetry, no solar panels, and some small protuberance.

Pretty sure its Dragon. It has some weird perspective going on with the solar array covers.

Ah. I see my mistake
I misinterpreted a lighting line on the solar array cover and the stylized disconnect.
Carry on!

[gongora]

[Spaceflight Now] Falcon 9 performs extended mission in test for future U.S. military launches

A SpaceX official said Friday that engineers added baffles to the second stage tanks to help prevent liquid propellant from pooling on the tank walls. The official said SpaceX’s earlier long-duration coast demonstrations, such as the STP-2 mission on the Falcon Heavy, proved the upper stage could perform maneuvers over several hours, but that engineers did not quite see the results they desired.