SpaceX F9 : Hera (asteroid mission) : CCSFS SLC-40 : 7 October 2024 (14:52 UTC)

[FutureSpaceTourist]

Launch highlights:

[FutureSpaceTourist]

Full SpaceX webcast rehost on YouTube:

[Targeteer]

https://twitter.com/cbs_spacenews/status/1843323310328676369

F9/Hera: A final thought: only a handful of rockets have taken off from Florida when the forecast the day before launch was 85% 'no-go' or worse; Hera now joins that short list; but it shows once again why managers do not like to call off a launch despite and initially bad forecast

[FutureSpaceTourist]

https://twitter.com/spacex/status/1843340069501055427

View from Falcon 9's second stage during the Hera mission

[ugordan]

Wow. Notice the sparkling in the stage 2 video? That is likely radiation hits on the imager arrays from passing through the Van Allen belts.

Yup. Enhanced by the fact that the stage was in darkness with only the low level onboard light present so exposure durations/gains were higher. Still looks pretty scary, though.

[FutureSpaceTourist]

https://twitter.com/theoldmanpar/status/1843362571921076448

Closer view of the #SpaceX #Hera launch for ESA from earlier today.

[LouScheffer]

Return of MVac deep throttling?  In the 2015 Falcon 9 Users Manual, the second stage could throttle down to 360 kN (81,000 lbf).  But in the 2021 User's Manual, it can only go as low as 626 kN (140,679 lbf).  So did SpaceX really remove the deep throttle capability?

The Hera mission offers a clue.   As in a post above, it was accelerating at 57.2 m/s just before burnout.  And since it launched on the first day of the window, we can guess the mass fairly accurately - it will be empty stage 2 mass, fuel reserve, and spacecraft.  It's thought the second stage empty mass is about 4 tonnes, reserves at 1% would be 1.1 tonne, and the spacecraft is 1.1 tonne.  So altogether about 6.2 tonnes.   This gives a thrust of 355 kN, very nearly equal to the previously quoted minimum.  So I suspect that's the real minimum throttle, and the new user's manual for some reason quotes a higher number.

[FutureSpaceTourist]

https://twitter.com/spacex/status/1843374114498850975

Falcon 9 launches the @ESA Hera mission to interplanetary transfer orbit from Florida

[GWR64]

Return of MVac deep throttling?  In the 2015 Falcon 9 Users Manual, the second stage could throttle down to 360 kN (81,000 lbf).  But in the 2021 User's Manual, it can only go as low as 626 kN (140,679 lbf).  So did SpaceX really remove the deep throttle capability?

The Hera mission offers a clue.   As in a post above, it was accelerating at 57.2 m/s just before burnout.  And since it launched on the first day of the window, we can guess the mass fairly accurately - it will be empty stage 2 mass, fuel reserve, and spacecraft.  It's thought the second stage empty mass is about 4 tonnes, reserves at 1% would be 1.1 tonne, and the spacecraft is 1.1 tonne.  So altogether about 6.2 tonnes.   This gives a thrust of 355 kN, very nearly equal to the previously quoted minimum.  So I suspect that's the real minimum throttle, and the new user's manual for some reason quotes a higher number.

Maybe you should subtract that. So 981-626 kN. What a mistake in the Users Manual.

However, the launch was a great success for everyone involved.

[FutureSpaceTourist]

https://twitter.com/_rykllan/status/1843374067908575362

Recent launch of #Hera mission via #SpaceX's #Falcon9 vehicle

#Space #ESA

B1061: 23 launches in under 4 years

[FutureSpaceTourist]

Launch photos from ESA flickr

[Targeteer]

I may regret asking, but how is Goldstone still in contact with Hera 7 hours after launch?  When will the earth's rotation cause Loss of signal? Update Goldstone just lost contact...

[Steven Pietrobon]

I wasn't paying attention and missed that this launch was on! Fortunately, archive.org captured the press kit but their software doesn't capture the main image. I used an image that was posted on X instead.

https://web.archive.org/web/20241007041855/https://www.spacex.com/launches/mission/?missionId=hera

[catdlr]

Congratulations to ESA and SpaceX on a fantastic launch and start of mission operations!

I don't think I've ever seen an L-1 weather forecast as low as 15% GO and see it launch

A reminder that this thread is just for the launch. On-going Hera operations belong in the dedicated Hera thread:

https://forum.nasaspaceflight.com/index.php?topic=47135.0

After reading and catching up on this launch, I didn't see any congratulations to FutureSpaceTourist and his complete launch coverage on NSF Forums.  Thank you, FST.   Tony

[FutureSpaceTourist]

https://twitter.com/_mgde_/status/1843419690607296567

Hera, the heavenly heroine, was hastily hurled into the high heavens, narrowly navigating the portending winds of a hurricane, nefarious & near.

📸 - @NASASpaceflight

[FutureSpaceTourist]

ESA highlights video:

[Targeteer]

Goldstone is supporting Hera again.

[markbike528cbx]

Does anyone have info, or even a swag on how deep into the "landing burn"  propellant volume this first stage went?
I can't imagine very deep, as 9 engines use more, and what is a 9 second burn with one engine is a one second burn with 9.  A little too much and you have an anomaly. 

Yes, I know the center is throttled down a bit on landing, but that just emphasizes my point.

[LouScheffer]

Does anyone have info, or even a swag on how deep into the "landing burn"  propellant volume this first stage went?
I can't imagine very deep, as 9 engines use more, and what is a 9 second burn with one engine is a one second burn with 9.  A little too much and you have an anomaly. 

Yes, I know the center is throttled down a bit on landing, but that just emphasizes my point.

To first order, the re-entry burn (to keep the F9 from melting on re-entry) takes about 20 seconds on 3 engines, or about 60 engine-seconds.  The landing burn takes about 30 seconds on one engine.  So a total of 90 engine-seconds.  So using the fuel it would otherwise need for landing, the booster can fire all nine engines for an additional 10 seconds.  At this point, it's accelerating at about 3g, so it will stage about 300 m/s faster than it would on an ASDS recovery mission.

[LouScheffer]

Upon further review, this is not the right way to find the difference between an expendable and ASDS mission.  Using time and acceleration is iffy, as throttling can affect both.  Better to use the rocket equation, which uses only masses and ISP. (Plus computing it this way agrees with the data on SpaceX webcasts.  That's always a plus.)

The first part, the 90 engine-seconds is fine.  And all of this, except perhaps the last few seconds, will be at full throttle since that minimizes gravity losses.  Now each engine, with a thrust of 845 kN and an ISP of 311, eats 277 kg/sec, so 90 seconds take 25 tonnes of fuel.  It's a little less, from both the throttling and the 1-3-1 sequence for the entry burn, so not all engines are on for all 20 seconds.  On the other hand there needs to be some margin kept.  Let's say 24 tonnes for landing fuel.

Now compute the delta-V with and without using that margin.  Assuming start fuel = 436 tonnes, empty first stage mass = 27 tonnes,  second stage + payload is 118.5 tonnes, then the difference in delta-V is 454 m/s, all else being equal.

But all else is *not* equal.  The payload is light (1.2 tonnes) rather than the usual 6 tonne comsat.  Plus there is no need for legs, so take 2 tonnes off the dry mass of the first stage.  Combined that gives a hypothetical staging difference of about 560 m/s.

We can compare this to the speeds shown on the SpaceX webcasts.  Hera staged at 10,220 km/hr.  Other flights of booster 1061 staged at speeds somewhat above and below 8200 km/hr.   So the measured difference is about 2020 km/hr, or 556 m/s faster when expendable.  So everything seems more or less consistent.