SpaceX Falcon 9 : NROL-85 : Vandenberg : 17 April 2022 (13:13 UTC)

[Galactic Penguin SST]

The F9 2nd stage either firing its Merlin Vac or its RCS just before de-orbiting on its 2nd orbit as seen from Mauna Kea, Hawaii just after 15:00 UTC:

[Vettedrmr]

I thought that was a tank depress after completing the deorbit burn.

[Targeteer]

Already spotted in orbit  http://www.satobs.org/seesat/Apr-2022/0084.html

http://www.satobs.org/seesat/Apr-2022/0094.html

"So far, the apparent absence of a secondary payload is interesting. Either this
is not an INTRUDER/NOSS mission after all; or it is an improved version of
INTRUDER that now only needs one single satellite (they once started with
three); or we somehow missed the second payload."

[ChrisC]

Here is a plot of the NROL-85 first stage webcast telemetry.
This is SpaceX's first launch of an Intruder pair of satellites, so there is nothing to directly compare the profile with. Yet.

As always, thank you OneSpeed for this excellent data, and the extra analysis of the vertical accel component this time.

When I watch these booster returns, I've gotten used to seeing a few numeric milestones during the webcast, and they seemed way different this time.  Normally, the entry burn starts as the booster is accelerating (falling) through ~8000 km/h (2200 m/s) and then stops as the booster has been braked down to ~5000 km/h (1400 m/s).  Those are very rough numbers (give or take 10-15%) but that's what I've been used to -- 8000 at start and 5000 at end.  On this webcast, the numbers were much lower, with entry burn starting at 4600 km/h (1300 m/s) and ending at ~2500 km/h (700 m/s).  Is this because of the lofted profile of an RTLS landing, and the speed that SpaceX is showing is the TOTAL speed with BOTH vertical and horizontal components, and an RTLS landing has much less horizontal component than a downrange landing?  If so then I guess I've just gotten used to the downrange numbers.

I don't think the particular orbit it's going to makes that much of a difference, so those two classes of launches should be comparable within their respective groups, right?

[Joffan]

Here is a plot of the NROL-85 first stage webcast telemetry.
This is SpaceX's first launch of an Intruder pair of satellites, so there is nothing to directly compare the profile with. Yet.

As always, thank you OneSpeed for this excellent data, and the extra analysis of the vertical accel component this time.

When I watch these booster returns, I've gotten used to seeing a few numeric milestones during the webcast, and they seemed way different this time.  Normally, the entry burn starts as the booster is accelerating (falling) through ~8000 km/h (2200 m/s) and then stops as the booster has been braked down to ~5000 km/h (1400 m/s).  Those are very rough numbers (give or take 10-15%) but that's what I've been used to -- 8000 at start and 5000 at end.  On this webcast, the numbers were much lower, with entry burn starting at 4600 km/h (1300 m/s) and ending at ~2500 km/h (700 m/s).  Is this because of the lofted profile of an RTLS landing, and the speed that SpaceX is showing is the TOTAL speed with BOTH vertical and horizontal components, and an RTLS landing has much less horizontal component than a downrange landing?  If so then I guess I've just gotten used to the downrange numbers.

I don't think the particular orbit it's going to makes that much of a difference, so those two classes of launches should be comparable within their respective groups, right?

Yes, I'm sure that's due to the boostback for RTLS. The booster is travelling relatively slowly horizontally after the boostback, compared to its partial ramp up to orbital velocity otherwise. You can see how much speed has been scrubbed off there, and the very slight upcurve at the end of the boostback burn represents the speed added to go back to the landing pad. The other effect I noticed was that the re-entry burn started much lower, for much the same reasons; I think it was under 40km rather than the 55-60 I'm used to, and we were still not close to terminal velocity.

[Comga]

If I smooth the slope of the altitude values I can derive the vertical component of the velocity vector (Vy), which is the yellow line in the plot below. Above 100km altitude, there is a lot of noise, because the webcast altitude goes from displaying a single decimal point (e.g. 99.9km) to an integer (e.g. 100km).

Nevertheless, by drawing a straight line between the start and end of the three engine part of the boostback burn (in black), you can see that there is a change in slope of Vy, so this rocket does have a slight pitch down during boostback (also visible in the webcast).

As well, the magnitude of the velocity vector (speed) and the vertical component Vy intersect at about the same point as the acceleration is -1g (freefall). If |V| and Vy are equal, then from Pythagoras, the horizontal component of the velocity (Vx) must be zero at that point. After that time, the acceleration goes positive for a few seconds, as Vx goes increasingly negative (and heads uprange to the landing pad).

This is brilliant.
The SpaceX webcast has always shown two data series, altitude and velocity.
After extracting these series (still very impressive, OneSpeed) the velocity was differentiated to yield acceleration.
That was adequate for the pseudo-one-dimension of launch, but ASDS and RTLS landings are decidedly two dimensional.
Here the altitude has been differentiated to yield vertical velocity.
The two velocities, total and vertical, can be used to derive the horizontal component and flight angle.
All this may be too much to add to the regular graphs, particularly when comparing one flight to a previous one, but this makes it much more descriptive.
Thanks OneSpeed!

[OneSpeed]

...
The two velocities, total and vertical, can be used to derive the horizontal component and flight angle.
All this may be too much to add to the regular graphs, particularly when comparing one flight to a previous one, but this makes it much more descriptive.
...

Thanks for everyone's positive comments, but I think I need to be careful not to overreach here. I can add Vx, FPA and even downrange distance by integrating Vx, but they are particularly noisy.

That said, there are some valid inferences we can make. E.g. in ballistic flight above about 50km, the horizontal velocity is essentially constant, and at apogee, it is equal to the speed, which from the plot below is 354m/s. For an ASDS launch, like the recent Starlink 4-12 mission, Vx was 1,981m/s at apogee, over a quarter of orbital velocity. So, as ChrisC suggests, the ASDS entry can utilise much more glide to slow the vehicle, at higher altitudes and velocities than for RTLS.

[alugobi]

I thought that was a tank depress after completing the deorbit burn.

Are deorbiting stages intentionally made to tumble like that?

[Jarnis]

Pretty sure that is the side effect of the propellant dump and since the stage is trash at that point, why would they care if it starts to tumble from the dumping?

[LouScheffer]

Are deorbiting stages intentionally made to tumble like that?

In some cases (don't know about this one) rockets are deliberately tumbled so any residual thrust does not add up in any particular direction.  This makes the stage's trajectory after venting more predicitable.

[baldusi]

Are deorbiting stages intentionally made to tumble like that?

In some cases (don't know about this one) rockets are deliberately tumbled so any residual thrust does not add up in any particular direction.  This makes the stage's trajectory after venting more predicitable.

Increases drag, too.

[Rondaz]

Hobbyists are tracking the newly launched US NRO signals intelligence satellie USA 327 in a 1007 x 1206 km x 63.4 deg orbit.,
as expected. This type of satellite usually releases a subsatellite, but that hasn't been observed yet in this case.

https://twitter.com/planet4589/status/1516398569288310784

[billh]

I thought that was a tank depress after completing the deorbit burn.

Are deorbiting stages intentionally made to tumble like that?

This was my question, too. I thought passivating the stage was only necessary if it was not going to be deorbited.

[Targeteer]

http://www.satobs.org/seesat/Apr-2022/0112.html  USA 327: updated elements

[friendly3]

Still no news about the fairings recovery?

[Rondaz]

NROL-85 launch

https://twitter.com/_TomCross_/status/1517917318654820352

[Yiosie]

Interesting SpaceNews article regarding the change in launch site and booster for this mission:

SpaceX moved NROL-85 from the Cape to Vandenberg at no extra cost, in exchange for reusing booster [dated May 6]

The National Reconnaissance Office’s NROL-85 mission launched April 17 by SpaceX was originally scheduled to fly from Cape Canaveral, Florida. But just 12 months before the launch, the NRO informed SpaceX it needed to send its payload to a different orbit so the launch had to be moved to the western range at Vandenberg Space Force Base, California.

“This was a challenge,” NROL-85 mission manager Maj. Jonathan Schirner said this week on the NRO’s “The Dish” podcast.

National security space launch missions are rarely, if ever, moved from coast to coast on such short notice, Schirner said. “It’s the first time we’ve done a range change at the 12 month mark in the NSSL timeframe.”

<snip>

The NRO and SpaceX worked out a deal to move NROL-85 to the West Coast at no extra cost to the government and in exchange the NRO agreed to fly the mission on a reused first stage that had previously flown another NRO mission.

Under the agreement, SpaceX would launch NROL-87 in February at Vandenberg and reuse the boost for NROL-85 in April. Schirner said the deal also was possible because the Space Force’s Space Systems Command was able to examine the recovered booster and approve it for reuse in just two months, a much shorter than usual turnaround.

[TrevorMonty]

Saved SpaceX and Dod money but just as importantly got DoD onboard with reuseable boosters.

Sent from my SM-T733 using Tapatalk

[baldusi]

Saved SpaceX and Dod money but just as importantly got DoD onboard with reuseable boosters.

Sent from my SM-T733 using Tapatalk

DoD was already in, NRO was converted, which is probably as tough a cookie as clients in the space business go.

[Jarnis]

This move explains why Cape has a new shiny booster that is going to do a Starlink mission as the first flight. It was the "leftover" from NRO when the payload moved to used booster on the west coast.