SpaceX Falcon 9 / Dragon 2 : SpX-DM2 : May 30, 2020 : DISCUSSION

[Lars-J]

1st stage smoother than SRBs, 2nd stage rougher than Shuttle post SRB sep.  Probably reflective of the mass of Shuttle versus Dragon and a throttled down Merlin being chuggier.

Makes sense. And on the first stage you have 9 engines that effectively smooth out each others vibrations, vs just one engine on the upper stage. But the mass difference is probably a huge factor too.

[kevinof]

yeah that's what is sounded like - the S2 is also powerful plus is a lot closer to the Dragon so you will hear everything it does. Maybe that's what they meant by huffing and puffing?

1st stage smoother than SRBs, 2nd stage rougher than Shuttle post SRB sep.  Probably reflective of the mass of Shuttle versus Dragon and a throttled down Merlin being chuggier.

[Hog]

Also noted that Shuttle pulled more G's, which of course was 3 g's as the 3 RS-25D's were throttled down to 67-72% for the last 30+ seconds of powered flight.

[NavySpaceFan]

Okay, what was that piece of music they just played at the end of the broadcast?  It sounded like a re-arrangement of John William's Mission Theme.

[saturnapollo]

Did Doug bump his head?  He kept wiping the right side of his forehead and looking at his hand as if he had a small nick.

Must have done as Cassidy had to go and get a tissue for him.

By the way, Endeavour will be spelled with a "u"

[Lars-J]

I watched the first part of the press conference / media briefing, and was very disappointed with the quality of questions. What exactly do some of these journalists think that NASA has an obligation or even ability to do about social unrest? All NASA can do is offer inspiration, for those that want to listen. This mission had been planned for months (years even), so if another news event overshadows it, what can they do?

[SteveU]

I watched the first part of the press conference / media briefing, and was very disappointed with the quality of questions. What exactly do some of these journalists think that NASA has an obligation or even ability to do about social unrest? All NASA can do is offer inspiration, for those that want to listen. This mission had been planned for months (years even), so if another news event overshadows it, what can they do?

Have to strongly agree with you.  I had to turn it off half way through FIRST question.

[DigitalMan]

I watched the first part of the press conference / media briefing, and was very disappointed with the quality of questions. What exactly do some of these journalists think that NASA has an obligation or even ability to do about social unrest? All NASA can do is offer inspiration, for those that want to listen. This mission had been planned for months (years even), so if another news event overshadows it, what can they do?

Unfortunately, I don't think it is possible to eliminate corruption, hatred, etc., no matter what you do or don't do. Eliminating efforts to make life better for humans by exploring and learning will likely have the opposite effect that people want.

[averow45]

Around the time of the manual piloting test near station, I heard the commentators on the SpaceX webcast say that the actual piloting was very close to the sim piloting; control in X and Z axis nice and tight, Y just a little sloppy just like sim.

However, this same commentator said that the lift off experience was not the same as expected. Does anyone know what the lift off experience was and how it varied from the sim?

Was the liftoff difference a difference between Shuttle and Falcon liftoffs, or between modeled and actual Falcon performance?

My interpretation was difference between modeled and actual since they stated it was different than expected. But I haven't been able to find any detail. Will be very interesting to learn.

My interpretation was, that Dragon ascent had been more dynamic (higher vibrations?), than they expected. Of course, simulators  could not prepare then for the moving sensations.

Thanks. Just found the piece of video Bob is talking about this. He said observation uphill had minor surprises in terms of the way vehicle is moving and shaking. Taking into orbit can tell fighting against the earth.

For what it is worth there was discussion during the ARES-1 program in modelling that the ride could be potentially so filled with vibrations and low frequency noise that the astronauts might have trouble with seeing screens and pressing keys and/or screens. I wonder if the test pilots were alluding to this kind of noise and/or vibration with yesterdays ascent ?

[IanO]

There was a moment in the SpaceX feed a few minutes before liftoff where one of the ground cameras looked like it was inundated by a sprinkler.  Anyone know what caused that?

[salpun]

There was a moment in the SpaceX feed a few minutes before liftoff where one of the ground cameras looked like it was inundated by a sprinkler.  Anyone know what caused that?

Water tower gets filled to over topping during the count. Happens every launch, maybe new camera location.

[clippie]

I just got on so this may have already been mentioned.
The interior of the dragon looked noticeably structurally “clean” compared to other human capsules.

[Coastal Ron]

For what it is worth there was discussion during the ARES-1 program in modelling that the ride could be potentially so filled with vibrations and low frequency noise that the astronauts might have trouble with seeing screens and pressing keys and/or screens. I wonder if the test pilots were alluding to this kind of noise and/or vibration with yesterdays ascent ?

The crew reported that the ride was smooth. Falcon 9 uses liquid fueled engines, which don't have much vibration.

The Ares I was essentially a Shuttle SRB, which is a solid rocket booster, and solid rocket engines are notorious for having a lot of vibration due to the uneven burning of the solid fuel, and as the SRB casing is emptied of fuel the casing oscillates. Here is an article about what they were trying to do to mitigate the vibrations on Ares I.

But if you watch the capsule video you'll see that the ride inside the capsule is pretty smooth.

[sanman]

Is there any footage yet available of Dragon interior during the actual lift-off?

I've seen people say that they experienced 2.5 G's during ascent, and the astronauts themselves said that acceleration forces were less than Shuttle but that the ride up was bumpier (latter makes sense, as it's a smaller vehicle).

Also, did Doug experience a slight head-scrape when initially entering into the ISS?

[sanman]

I watched the first part of the press conference / media briefing, and was very disappointed with the quality of questions. What exactly do some of these journalists think that NASA has an obligation or even ability to do about social unrest? All NASA can do is offer inspiration, for those that want to listen. This mission had been planned for months (years even), so if another news event overshadows it, what can they do?

In the future, it would be best to pre-record the questions and pick through them to select the ones most worth posing to the group. I don't know what they expected the NASA administrator to answer about wider society, but activists will always seek an outlet for themselves.

[FutureSpaceTourist]

Love this by Michael:

https://twitter.com/nextspaceflight/status/1267217099346214914

From the launch pad of Apollo 11 and 82 Space Shuttle missions, SpaceX begins the next chapter in U.S. human spaceflight.

📸 NASA, SpaceX

[Kabloona]

For what it is worth there was discussion during the ARES-1 program in modelling that the ride could be potentially so filled with vibrations and low frequency noise that the astronauts might have trouble with seeing screens and pressing keys and/or screens. I wonder if the test pilots were alluding to this kind of noise and/or vibration with yesterdays ascent ?

The crew reported that the ride was smooth. Falcon 9 uses liquid fueled engines, which don't have much vibration.

The Ares I was essentially a Shuttle SRB, which is a solid rocket booster, and solid rocket engines are notorious for having a lot of vibration due to the uneven burning of the solid fuel, and as the SRB casing is emptied of fuel the casing oscillates. Here is an article about what they were trying to do to mitigate the vibrations on Ares I.

But if you watch the capsule video you'll see that the ride inside the capsule is pretty smooth.

During the PAO event when Bob and Doug were welcomed into ISS and answered questions from the ground, Bob did say they were a bit surprised at how smooth the first stage burn was, compared to Shuttle.

But he went on to say that they had expected the stage 2 burn to get a lot smoother, but in fact the rocket was "huffing and puffing" all the way to orbit, and "we were definitely riding a dragon," that it was "not quite the same smooth ride as Shuttle" during the stage 2 burn.

The "huffing and puffing" sounds like a reference to chugging or pogo oscillation, probably for reasons suggested upthread  (much lower vehicle mass than Shuttle, one engine vs. multiple engines, etc.)

So apparently stage 2 was an unexpectedly bumpy ride as compared to Shuttle (after SRB sep).

[lonestriker]

1st stage smoother than SRBs, 2nd stage rougher than Shuttle post SRB sep.  Probably reflective of the mass of Shuttle versus Dragon and a throttled down Merlin being chuggier.

For those saying the entire F9 flight was smooth, the above is what Bob and Doug said in their various presentations and Q&A sessions.  First stage to MECO was much smoother than Shuttle since the Shuttle's SRBs were very rough.  F9 S2 was "huffing and puffing" vs. Shuttle's smoother post-SRB ride; probably due to the above speculation about mass and  proximity to the engines.

I was disappointed in NASA's post docking ceremony.  Far too many politicians taking up valuable time making the ceremony more about them and their politics than the accomplishment and hard work of NASA and SpaceX.  Bob and Doug didn't even get a chance to give a speech other than general responses to questions.  Cruz was too long-winded.  I gagged when the JSC Congressional House rep asked what "SECO" was and was mostly clueless.  At least the last rep had the decency to just say "congrats" and let them mostly be.  There was no mention of the capture-the-flag prize.  Doug really should have symbolically touched the flag at a minimum during the ceremony.  When the ceremony ended and the NASA livestream stopped, I had to do a double take and ask "was that it?!?!?"

The post-docking briefing questions were mostly terrible.  I think people really did run out of questions to ask at this point.  I'm all for equal justice, but the NASA administrator isn't going to solve the issue and wasting everyone's time with variations of the same question over and over again is counter-productive.  Bridenstine was already asked several times about the protests and the mission within the context of America's current events and answered as well as could be expected.  No need for reporters to keep asking variations on the same question just to hear themselves talk.

All that aside, I am very happy that the launch and docking went more or less flawlessly.  The weather delay was actually good in that I was able to watch almost all of the webcast (sleeping when Bob and Doug slept

[JimO]

Any other images from ISS of the ascent?

 Here's the links: COMPARE OTHER ISS VIEWS OF LAUNCHES
http://satobs.org/seesat_ref/misc/Soyuz_launch_4.pdf

Observations of the Soyuz launch on December 3, 2018:
[plus obs of Soyuz launch abort, from ISS, a few months earlier]
http://satobs.org/seesat_ref/misc/181203-soyuz_launch.pdf

http://satobs.org/.../Russian_Missile_Launch_Viewed_from...
http://www.jamesoberg.com/ISS_crew_spots_second_russian...

[Mookerdud]

I just got on so this may have already been mentioned.
The interior of the dragon looked noticeably structurally “clean” compared to other human capsules.

I assume the next one will be stuffed with more cargo, and 4 crew members. So I think it will look less clean already.