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

[igloz]

This gives about 750 kg for RTLS and 2100 kg for ASDS recovery.

And IXPE mass is 337...

[Rondaz]

The crane is now in its stowed position, Bob should be departing soon to catcth up with Doug for IXPE.

https://twitter.com/Kyle_M_Photo/status/1467717447528718336

[LouScheffer]

This gives about 750 kg for RTLS and 2100 kg for ASDS recovery.

And IXPE mass is 337...

I think there are at least 3 potential reasons for this:

(a) Worries about crushing the payload, as OneSpeed pointed out.  The Merlin Mvac can throttle down to 625,000 N, according to SpaceX.  The second stage is thought to mass about 4.5 tonnes dry.  So if it needs to run to depletion (perhaps the 3 sigma worst case), then that would be more than 12Gs.  Since IXPE was designed for Pegasus, it likely has a design limit of 9Gs.   So SpaceX can't use the last 2.5 tons of fuel, even in the worst case.

(b) They need to deorbit the stage.  The calculation I did converted it to an escape orbit, which needs no disposal.   This mission does.

(c) General engineering conservatism, on the part of NASA, SpaceX, or IXPE.  Barge recovery is probably only a few million more than RLTS.  For that you get bigger margins, less stress on IXPE, plenty of fuel for disposal, and so on.

[Ken the Bin]

L-2 weather forecast.  80% 'Go' for both December 9 and December 10.  Upper-Level Wind Shear Risk and Booster Recovery Risk are Low-Moderate for December 9.  All other Additional Risk Criteria are Low for both days.

[Rondaz]

Weather 80% Favorable for Thursday’s IXPE Launch

James Cawley Posted on December 6, 2021

Weather officials with Cape Canaveral Space Force Station’s 45th Weather Squadron predict an 80% chance of favorable weather conditions for Thursday’s early morning launch of NASA’s Imaging X-Ray Polarimetry Explorer (IXPE) spacecraft from the Space Coast, with the cumulus cloud rule and thick cloud layer rule serving as the primary weather concerns.

IXPE is scheduled to launch aboard a SpaceX Falcon 9 rocket from Kennedy Space Center’s Launch Complex 39A on Dec. 9, 2021, at 1 a.m. EST. IXPE will study the polarization of X-rays coming to us from some of the universe’s most extreme sources, including black holes and dead stars known as pulsars.

The launch is managed by NASA’s Launch Services Program, based at Kennedy.

On Tuesday, Dec. 7, NASA will hold an IXPE payload briefing at 1 p.m. and a prelaunch news briefing at 5:30 p.m. Live launch coverage will begin Dec. 9 at 12:30 a.m. All will be broadcast on NASA Television, the NASA app, and the agency’s website.

https://blogs.nasa.gov/ixpe/2021/12/06/weather-80-favorable-for-thursdays-ixpe-launch/

[Rondaz]

Departure! Bob is outbound for IXPE fairing recovery operations.

https://twitter.com/SpaceOffshore/status/1467950755978035205

[wannamoonbase]

Bob is a work horse.  After trying several different ships and recovery attempts it seems that Bob and Doug just keep delivering!

I love that SpaceX is reusing fairings and saving that money.

[markbike528cbx]

I wonder why this mission is not RTLS? A lightweight payload to LEO...

  I had the same question, thanks for asking it first :-)

This gives about 750 kg for RTLS and 2100 kg for ASDS recovery.

And IXPE mass is 337...

I think there are at least 3 potential reasons for this:

(a) Worries about crushing the payload, as OneSpeed pointed out.  The Merlin Mvac can throttle down to 625,000 N, according to SpaceX.  The second stage is thought to mass about 4.5 tonnes dry.  So if it needs to run to depletion (perhaps the 3 sigma worst case), then that would be more than 12Gs.  Since IXPE was designed for Pegasus, it likely has a design limit of 9Gs.   So SpaceX can't use the last 2.5 tons of fuel, even in the worst case.

(b) They need to deorbit the stage.  The calculation I did converted it to an escape orbit, which needs no disposal.   This mission does.

(c) General engineering conservatism, on the part of NASA, SpaceX, or IXPE.  Barge recovery is probably only a few million more than RLTS.  For that you get bigger margins, less stress on IXPE, plenty of fuel for disposal, and so on.

As to why the 0 degree inclination, https://arxiv.org/pdf/2102.06475.pdf  says it is to avoid the South Atlantic Anomaly
A Study of background for IXPE  by  F. Xie  et al.

.....and optimizes the observing efficiency by minimizing the passage in the South Atlantic Anomaly (SAA), ...

I searched the thread for the WHY of the inclination but couldn't find it. Apologies if I missed something or repeating stuff.

[Rondaz]

Weather Improves to 90% Favorable for Thursday’s IXPE Launch

James Cawley Posted on December 7, 2021

The weather outlook for Thursday’s early morning launch of NASA’s Imaging X-Ray Polarimetry Explorer (IXPE) spacecraft from Kennedy Space Center bumped up in a positive direction. Weather officials with Cape Canaveral Space Force Station’s 45th Weather Squadron now predict a 90% chance of favorable conditions for liftoff, increasing by 10% from a day ago. The cumulus cloud rule is the primary weather concern.

IXPE is scheduled to launch aboard a SpaceX Falcon 9 rocket from the Florida spaceport’s Launch Complex 39A on Dec. 9, 2021, at 1 a.m. EST. The launch is managed by NASA’s Launch Services Program, based at Kennedy.

IXPE is the first satellite dedicated to measuring the polarization of X-rays from a variety of cosmic sources, such as black holes and neutron stars.

Today, NASA will hold an IXPE payload briefing at 1 p.m. and a prelaunch news briefing at 5:30 p.m. Both will be broadcast on NASA Television, the NASA app, and the agency’s website. Live launch coverage will begin Dec. 9 at 12:30 a.m.

https://blogs.nasa.gov/ixpe/2021/12/07/weather-improves-to-90-favorable-for-thursdays-ixpe-launch/

[jjyach]

Rollout of the rocket with payload has started

[Rondaz]

NASA’s IXPE Rolls out to Launch Pad at Kennedy

James Cawley Posted on December 7, 2021

NASA’s Imaging X-Ray Polarimetry Explorer (IXPE) spacecraft, atop a SpaceX Falcon 9 rocket, rolled out of Kennedy Space Center’s Launch Complex 39A hangar to the launch pad on Wednesday, Dec. 7, at 12:46 p.m. EST. The rocket and spacecraft are expected to go vertical this evening.

NASA’s first mission dedicated to measuring X-ray polarization, IXPE is targeted to lift off from Kennedy on Thursday at 1 a.m. The launch is managed by NASA’s Launch Services Program, based at Kennedy.

The IXPE spacecraft includes three space telescopes with sensitive detectors capable of measuring the polarization of cosmic X-rays, allowing scientists to answer fundamental questions about extremely complex environments in space where gravitational, electric, and magnetic fields are at their limits. The project is a collaboration between NASA and the Italian Space Agency.

On Dec. 9, tune in to NASA Television, the NASA app, or the agency’s website for a live broadcast – or stay right here for a live blog to take you through the launch day events.

https://blogs.nasa.gov/kennedy/2021/12/07/nasas-ixpe-rolls-out-to-launch-pad-at-kennedy/

[vaporcobra]

IXPE pre and post encapsulation.

https://images.nasa.gov/details-KSC-20211201-MH-FMX01-0001-IXPE_Spacecraft_Prep_for_Encapsulation-3291800

https://images.nasa.gov/details-KSC-20211202-MH-JBS01-0001-IXPE_Payload_Encapsulation-3292557

Edit: And the rollout image from the above blog post.

[Rondaz]

NASA | NASA'S Imaging X-ray Polarimetry Explorer prelaunch news conference

[Ken the Bin]

SpaceX has updated their Launches webpage:

SpaceX is targeting Thursday, December 9 for Falcon 9’s launch of NASA’s Imaging X-ray Polarimetry Explorer (IXPE) mission to low Earth orbit from historic Launch Complex 39A (LC-39A) at NASA’s Kennedy Space Center in Florida. The 90-minute launch window opens at 1:00 a.m. EST (6:00 UTC). A backup opportunity is available on Friday, December 10 with the same 90-minute launch window, should it be needed.

This will be the fifth flight for this Falcon 9’s first stage booster, which previously supported launch of Crew-1, Crew-2, SXM-8, and CRS-23. Following stage separation, Falcon 9’s first stage will land on the Just Read the Instructions droneship, which will be located in the Atlantic Ocean.

A live webcast of this mission will begin about 15 minutes prior to liftoff.

[Ken the Bin]

SpaceX webcast (video id CpmHsN5GUn8):

[Ken the Bin]

NASA webcast (video id JGij0x0PA_Q):

[Conexion Espacial]

SpaceX IXPE mission patch

[Ken the Bin]

The 45th Weather Squadron finally posted the L-1 weather forecast publicly.  90% 'Go' for December 9.  80% 'Go' for December 10.  Upper-Level Wind Shear Risk is Low-Moderate for December 9.  All other Additional Risk Criteria are Low.

[scr00chy]

SpaceX photos

[scr00chy]

NASA and SpaceX mission patches (enlarged, cleaned up and with transparent backgrounds)