SpaceX Falcon 9 : NASA IXPE : KSC LC-39A : 9 December 2021 (0600 UTC)

[lenny97]

I would love to see some SpaceX's "bullseye" stats, just like ULA.
With last night launch the in-orbit precision of Falcon 9 is even more interesting imo...

[LouScheffer]

I would love to see some SpaceX's "bullseye" stats, just like ULA.
With last night launch the in-orbit precision of Falcon 9 is even more interesting imo...

I don't think you are likely to see these from SpaceX.   Since they have a much larger second stage engine, (about 6 x bigger than the RL-10), likely their shut-off uncertainty is about 6x bigger as well.  Conversely, ULA is happy to show these, since their smaller engine gives them better injection accuracy.

I don't think this is a big issue for most customers.  A super-accurate injection saves some fuel which would otherwise be needed for correcting launch dispersions, but that's usually not a huge amount in the grand scheme of things.

[Comga]

I would love to see some SpaceX's "bullseye" stats, just like ULA.
With last night launch the in-orbit precision of Falcon 9 is even more interesting imo...

I don't think you are likely to see these from SpaceX.   Since they have a much larger second stage engine, (about 6 x bigger than the RL-10), likely their shut-off uncertainty is about 6x bigger as well.  Conversely, ULA is happy to show these, since their smaller engine gives them better injection accuracy.

I don't think this is a big issue for most customers.  A super-accurate injection saves some fuel which would otherwise be needed for correcting launch dispersions, but that's usually not a huge amount in the grand scheme of things.

If it’s not copyrighted, the “bullseye” graph is at least characteristic of ULA

Plus, as a fan of Edwin Tufte I find the bullseye graphs cutesy and uninformative.

We did see that the altitude at SECO 2 was 600 km, so to the extent that the display corresponds to the target, the orbit was spot on in altitude.

And yes, with a low thrust engine and a converging controller, one can get high accuracy, which may not be necessary but is very expensive.  The entire IXPE launch on Falcon 9 costs less than twice as much as a Centaur upper stage.

[RotoSequence]

A little late to ask to be sure, but out of curiosity, what kept IXPE from flying on Vega?

May be, 0° inclination of the deployment orbit.
(and of course high price)

0° inclination is one of Vega's specialties thanks to launching from Kourou at 5.17 degrees N. In theory, Vega is commercially cheaper than Falcon 9 at 32 million Euros.

[Barley]

However, it is important to remember that SpaceX webcasts display inertial velocity (velocity relative to the launch site), not  orbital velocity (velocity ignoring the rotation of the Earth).

I cannot understand that.  Could you explain in really basic terms using vectors, derivatives, norms and frames of reference what the "inertial velocity" displayed on the graph is?

I don't intend to kvetch about people using words differently, but the reason the above makes no sense to me is that velocity is a vector and the launch site (or anywhere on Earth) is a rotating non-inertial frame of reference, and clearly neither of these is intended in your explanation.

[Rondaz]

The Falcon 9 Second Stage in the upper atmosphere in front of a star filled sky.

https://twitter.com/erikkuna/status/1468923569472163845

[Rondaz]

IXPE is being tracked in a 588 x 603 km x 0.2 deg orbit - confirming the successful launch.
Catalog number is 49954.

https://twitter.com/planet4589/status/1468978613341069318

[Rondaz]

NASA's New X-Ray Telescope Is A Revolution in Astronomy and Launch Profiles

[RedSky]

Loved seeing the orbit change on the SpaceX display.  Just basically made a left turn onto the equator.

[scr00chy]

https://twitter.com/SpaceX/status/1468965191387779086?s=20

[OneSpeed]

I cannot understand that.  Could you explain in really basic terms using vectors, derivatives, norms and frames of reference what the "inertial velocity" displayed on the graph is?

I imprecisely abbreviated the scalar "magnitude of the inertial velocity" to "inertial velocity", but perhaps "inertial speed" would be more correct.

Mind you, in the recent ULA launch of Landsat 9, the orbital speed is actually labelled velocity, so I am not the only one to make this mistake. https://forum.nasaspaceflight.com/index.php?topic=41511.msg2294966#msg2294966

[zubenelgenubi]

Any news of launch time to the second, or millisecond?

[Rondaz]

Here's my reconstruction of the IXPE trajectory from SECO-1 through Stage 2 deorbit (white line represents stage 2, purple area in Pacific is the debris warning zone)

https://twitter.com/planet4589/status/1469046883876315139

[Rondaz]

https://twitter.com/planet4589/status/1469049907843633152

[punder]

https://twitter.com/planet4589/status/1469049907843633152

Wow! I’ve always been told such maneuvers are very energy-expensive. They must have had plenty of excess propellant to do that.

[russianhalo117]

https://twitter.com/planet4589/status/1469049907843633152

Wow! I’ve always been told such maneuvers are very energy-expensive. They must have had plenty of excess propellant to do that.

The spacecraft was built to the launch requirements/constraints to launch via a Taurus-XL/Pegasus-XL family launcher from an equatorial launch site. Like TESS et al the F9 is overkill but allows launching from a CONUS launch site instead of having to stand up launch operations from a remote site.

[su27k]

A little late to ask to be sure, but out of curiosity, what kept IXPE from flying on Vega?

NASA Policy Directive NPD 8610.12H:

a. It is NASA's policy to encourage and facilitate a viable, healthy, and competitive U.S. commercial space transportation industry. To that end, NASA shall plan for and utilize commercial space transportation services using space transportation vehicles manufactured in the U.S. for NASA and NASA-sponsored payloads to the maximum extent practicable.

There're some exceptions like the case of JWST, but none of that applies in this case.

[savantu]

I would love to see some SpaceX's "bullseye" stats, just like ULA.
With last night launch the in-orbit precision of Falcon 9 is even more interesting imo...

Does Centaur have the performance to launch IXPE like this ?

[Pete]

... In theory, Vega is commercially cheaper than Falcon 9 at 32 million Euros.

Yes, it is cheaper, in absolute cost per launch.
So is Rocketlab's Electron.

I fail to grasp what you try to say by this?
You are comparing apples to watermelons.

[Jim]

I would love to see some SpaceX's "bullseye" stats, just like ULA.
With last night launch the in-orbit precision of Falcon 9 is even more interesting imo...

Does Centaur have the performance to launch IXPE like this ?

yes