SpaceX F9 : SES-10 with reuse of CRS-8 Booster SN/1021 : 2017-03-30 : DISCUSSION

[edkyle99]

From the Update thread:

As of 18:57 UTC March 31, Space Track shows the following.

Falcon 9 R/B:  217 x 33,395 km x 26.31 deg
SES 10:  247 x 35,673 km x 26.18 deg

SFN gave a targeted 218 x 35,410 km x 26.2 deg insertion orbit. 

Makes me wonder if S2 burned to depletion.  That heavy of a bird would need about all the S2 has(especially with the S1 landing attempt).  If the track for S2 above was after sep and doesn't include any blow down....then John's "good enough" in the webcast was right and there was some underperforming experienced, but nothing way out of line. I just wouldn't think they would leave some performance on the table if they could help it.

To be clear, SpaceX has said that the payload ended up within its required orbital parameter range.  That said, I agree it does look like it might have been a depletion type cutoff, where the stage may have ended up just short of the perfectly ideal apogee and inclination.  Maybe only a momentary shortfall in burn time, since cutoff appeared to coincide with the time listed in the press kit.

Note that this stage ended up more than 2,000 km short on apogee, whereas the Echostar 23 stage is orbiting only 108 km short of its payload's insertion orbit apogee.  On the other hand, it is possible that the planned parameters listed by SFN subsequently changed on launch day based on temperatures, wind speeds, and the like (see Delta 280).

 - Ed Kyle

[cartman]

What is the deltaV difference between the upper stage and the satellite?

[edkyle99]

What is the deltaV difference between the upper stage and the satellite?

Currently about 44 m/s, not including the inclination change.  The difference between the current second stage orbit and the insertion goal listed by SFN is about 35 m/s, not including inclination difference.

 - Ed Kyle

[RedLineTrain]

My notes from Martin Halliwell's (SES) presser was that the target insertion was perigee of 218 km, apogee of 35,410 and inclination of 26.2 degrees on a 5,281.7 kg bird.  My calculations show that as -1789 m/s GTO.

So the second stage looks like it was 21 m/s off from what SES said.  My uneducated guess is that's well within the contracted parameters and any definition of success.

Edit:  To check my math...

Second stage:   217 x 33,395 km x 26.31 deg = -1810.9 GTO
SES presser:  218 x 35,410 km x 26.2 deg = -1789.2 GTO

The difference is 21.7 m/s

[winkhomewinkhome]

Это ещё цвето́чки, а я́годки впереди́.

"It's flowers and berries in front"  (blame Google Translate if not correct) ? is that a Russian aphorism for something along the lines of "you're just trying to make it look good?" or ??

"These are merely flowers, berries will appear later". This means that what you already got is not the worst part, the worse part is ahead.

But berries are delicious (the edible ones anyway). Why is that worse than the flowers? Seems better to me. Something along the lines of "these flowers portend tasty things to come".

While I agree with your positive interpretation; given the phrase is of Russian origin, the referred to berries are more than likely poisonous...thus. 

[stcks]

My notes from Martin Halliwell's (SES) presser was that the target insertion was perigee of 218 km, apogee of 35,410 and inclination of 26.2 degrees on a 5,281.7 kg bird.  My calculations show that as -1789 m/s GTO.

So the second stage looks like it was 21 m/s off from what SES said.  My uneducated guess is that's well within the contracted parameters and any definition of success.

Edit:  To check my math...

Second stage:   217 x 33,395 km x 26.31 deg = -1810.9 GTO
SES presser:  218 x 35,410 km x 26.2 deg = -1789.2 GTO

The difference is 21.7 m/s

And I'm showing a difference of about 37 m/s ... just goes to show there is more than one way to skin a cat. I am curious what are your methods for this calculation.  For subsync calculations I first raise apogee to GEO at perigee and then do a typical perigee raise and inclination change.

Heres the code if your interested (and I would like some peer review anyway): https://gist.github.com/anonymous/aa3397ea848d2e2d6986804f027e286e

[Comga]

My notes from Martin Halliwell's (SES) presser was that the target insertion was perigee of 218 km, apogee of 35,410 and inclination of 26.2 degrees on a 5,281.7 kg bird.  My calculations show that as -1789 m/s GTO.

So the second stage looks like it was 21 m/s off from what SES said.  My uneducated guess is that's well within the contracted parameters and any definition of success.

Edit:  To check my math...

Second stage:   217 x 33,395 km x 26.31 deg = -1810.9 GTO
SES presser:  218 x 35,410 km x 26.2 deg = -1789.2 GTO

The difference is 21.7 m/s

And I'm showing a difference of about 37 m/s ... just goes to show there is more than one way to skin a cat. I am curious what are your methods for this calculation.  For subsync calculations I first raise apogee to GEO at perigee and then do a typical perigee raise and inclination change.

Heres the code if your interested (and I would like some peer review anyway): https://gist.github.com/anonymous/aa3397ea848d2e2d6986804f027e286e

There is an mathematically determinable optimum with some small amount of plane change at perigee.
You could test this without determining the optimum.  Try 1 degree or 2.
The advantage is on the order the difference between the two calculations.

[RedLineTrain]

And I'm showing a difference of about 37 m/s ... just goes to show there is more than one way to skin a cat. I am curious what are your methods for this calculation.  For subsync calculations I first raise apogee to GEO at perigee and then do a typical perigee raise and inclination change.

Heres the code if your interested (and I would like some peer review anyway): https://gist.github.com/anonymous/aa3397ea848d2e2d6986804f027e286e

I also am using the LouScheffer's method that I transcribed to a spreadsheet. But I note that his method assumes a supersynchronous orbit.

[stcks]

I also am using the LouScheffer's method that I transcribed to a spreadsheet. But I note that his method assumes a supersynchronous orbit.

Yeah his method is perfect for super-sync injections (you'll note that I based mine on his code) but if you use it for sub-sync its going to be much less optimal.

[AncientU]

Here is a set of perspectives that I found encouraging:

Space Reporters React to SpaceX’s Breakthrough Moment in Spaceflight

http://observer.com/2017/04/space-reporters-react-to-spacexs-breakthrough-moment-in-spaceflight/

[AncientU]

This is also interesting from Eric Berger:

Every now and then I like to go back and read what Sen. Richard Shelby said about SpaceX in 2010. And then I laugh.

“This request represents nothing more than a commercially-led, faith-based space program.  Today, the commercial providers that NASA has contracted with cannot even carry the trash back from the space station much less carry humans to or from space safely.

“These providers have yet to live up to the promises they have already made to the taxpayer.  Not a single rocket or ounce of cargo has been launched since we met last year.  Instead of requiring accountability from these companies, the President’s budget proposes to reward these failed commercial providers with an additional bailout.

https://www.shelby.senate.gov/public/index.cfm/mobile/newsreleases?ID=25F3AD2E-802A-23AD-4960-F512B9E205D2

Eric Berger tweets
https://twitter.com/SciGuySpace

[Lar]

Here is a set of perspectives that I found encouraging:

Space Reporters React to SpaceX’s Breakthrough Moment in Spaceflight

http://observer.com/2017/04/space-reporters-react-to-spacexs-breakthrough-moment-in-spaceflight/

I don't turn off ad blockers, can someone net out the article?.. it sound really interesting.

[RotoSequence]

Here is a set of perspectives that I found encouraging:

Space Reporters React to SpaceX’s Breakthrough Moment in Spaceflight

http://observer.com/2017/04/space-reporters-react-to-spacexs-breakthrough-moment-in-spaceflight/

I don't turn off ad blockers, can someone net out the article?.. it sound really interesting.

It's a collection of paragraphs from about ten different commentators, newscasters, and bloggers about how they believe this launch was interesting and historic.

[Wolfram66]

With the stated mass to GTO of SES-10, do we know which landing burn profile was used?
looking at images posted of the landing it looks like the standard one engine landing burn.

also any update on delta V shortfall on the S2 2nd burn?

thanks in advance

[AncientU]

Here is a set of perspectives that I found encouraging:

Space Reporters React to SpaceX’s Breakthrough Moment in Spaceflight

http://observer.com/2017/04/space-reporters-react-to-spacexs-breakthrough-moment-in-spaceflight/

I don't turn off ad blockers, can someone net out the article?.. it sound really interesting.

A few of the comments (could have picked any handful at random):
Synopsis:

The Observer reached out to print, radio, and television reporters who have first-hand experience covering NASA and the commercial industry to get their reactions to the breakthrough reflight and what it might mean for the future of space exploration.

Brendan Byrne (WMFE 90.7 NPR Affiliate, ‘Are We There Yet’ Podcast) – “Accessibility is the key to exploration and rocket reusability is one way to make space open to more people. Thursday’s relaunch is a great proof of concept and if launch operators can duplicate those results, we’re on our way to becoming a spacefaring nation. SpaceX is leading the pack, but I wouldn’t be surprised if there’s many more on its heels. If we’re going to venture onto other planets, this is the technology we have to master.”

Sarah Fecht (Popular Science) – “One of the coolest things about being a journalist is being able to witness history being made, and that’s what we saw Thursday night. SpaceX has proven it’s possible to reuse a rocket that’s powerful enough to launch big payloads into orbit. They’ve still got a lot of work to do in terms of making the refurbishment process more efficient, but if reusable rockets result in the 100-fold savings that Elon Musk is predicting, that would be huge. Cheap and easy access to space means we could start thinking about building communities and economies in Earth orbit and on other worlds.”

James Dean (USA Today Network, Florida Today) – “It appears the old rules of rocketry no longer apply. Big rockets can not only land but fly again. How often and how efficiently will determine how big the industry impact is, but Musk has delivered on his promises so far (with a few setbacks along the way), and we know Bezos and Blue Origin are coming on strong with similar goals for reusability. It was a fun mission to watch, in part because it looked so routine.”

Michael Seeley (We Report Space) – “It’s difficult for me to put into words what I felt watching the SpaceX “flight proven” Falcon 9 successfully carry the SES10 satellite to orbit. In addition to the usual excitement of experiencing a launch, I also felt a sense of progression and curiosity about what that may lead to. I was there to see the “flight proven” first stage in its first life as it carried the CRS-8 payload to the International Space Station last year. I was also there to watch the first stage return to port atop the “Of Course I Still Love You.” And Thursday, we watched SpaceX take the next step, by proving that however cool it may be to land a rocket (and it is indeed cool), reusability of those rockets is essential. I am reminded, loudly, that there is a purpose, and vision, and an incredibly talented team executing this vision, making progress toward a goal to be an interplanetary species.”

Sawyer Rosenstein (Talking Space)- “Launch pad 39A has been home to some historic launches from moon landings to Hubble repair missions. It’s very fitting that SpaceX is using a historic site to make their own history. Having seen this booster launch back in April, one of the most spectacular things was watching the engineers react to the first ever barge landing. Now to see it launch and land again brings back those same goosebumps the engineers, and myself had on that day knowing that we’d witnessed a fundamental change in the future of spaceflight. This is the biggest step yet into the era of *actually* affordable reusable rockets.”

[cscott]

With the stated mass to GTO of SES-10, do we know which landing burn profile was used?
looking at images posted of the landing it looks like the standard one engine landing burn.

also any update on delta V shortfall on the S2 2nd burn?

thanks in advance

We have official confirmation that there was no shortfall.  I haven't heard anything about the landing burn, but I agree the photos look like a single-engine burn.

[edkyle99]

With the stated mass to GTO of SES-10, do we know which landing burn profile was used?
looking at images posted of the landing it looks like the standard one engine landing burn.

also any update on delta V shortfall on the S2 2nd burn?

thanks in advance

The second stage is most recently shown in a 238 x 33,403 km x 26.19 deg orbit.  Earlier, it was shown in a 217 x 33,395 km x 26.31 deg orbit.  Before the launch, SES said that the planned injection orbit was 218 x 35,410 km x 26.2 deg.  I haven't yet seen a Falcon 9 second stage move much after spacecraft separation.

SES 10 was originally tracked in a 247 x 35,673 km x 26.18 deg orbit, but this was more than a day after launch, so the satellite may have maneuvered a bit by then.  It has since then raised its perigee to 5,764 km and reduced inclination to 13.16 deg. 

SpaceX has said that SES 10 was injected into an orbit that met agreed parameters.  I wonder if this might have been a planned propellant depletion mission.  Such missions can have a wider acceptable orbit range than the more typical guidance cutoff missions. 

 - Ed Kyle

[Comga]

Landing video.

https://www.instagram.com/p/BSfJDjMFzwR/

Kind of bouncy on landing.

Everyone's a critic....
But thanks for the link.

[king1999]

SES 10 was originally tracked in a 247 x 35,673 km x 26.18 deg orbit, but this was more than a day after launch, so the satellite may have maneuvered a bit by then.  It has since then raised its perigee to 5,764 km and reduced inclination to 13.16 deg. 

That's a strawman argument. There was a tweet about the first burn which was quite a bit later (https://twitter.com/planet4589/status/848659317226078208). I suspect that 247 x 35,673 km x 26.18 deg was the original insertion orbit.

[nicfit]

SpaceX has said that SES 10 was injected into an orbit that met agreed parameters.  I wonder if this might have been a planned propellant depletion mission.  Such missions can have a wider acceptable orbit range than the more typical guidance cutoff missions. 

 - Ed Kyle

Exactly.
There is a minimum guaranteed apogee. F9 delivered much better than this.
Then there is a nominal calculated apogee, with associated tolerances. You always expect (or hope) to get there or above, betting on conservative computation. F9 delivered slightly below nominal but well within tolerances.