SpaceX F9 : Galaxy 31/Galaxy 32 : CCSFS SLC-40 : Nov. 12, 2022 (16:06 UTC)

[Robotbeat]

With this flight we can re-calibrate the loss of payload for recoverability.  This flight staged at 9777 km/hr = 2715 m/s.  The preceding G33/G34 flight (with recovery) staged at 8340 km/hr = 2316 m/s.   Thus the first stage provided roughly 400 m/s more (roughly because the differing payload masses will have some small effect on first stage dV).

Now making the usual second stage assumptions (fuel = 107t, empty mass + residual = 5.5t, ISP = 348), then how much can you increase the payload from the nominal 5.5t if the second stage needs to produce 400 m/s less?  Turns out it's 7.03t.  So any orbit the recoverable rocket can reach with a 5.5t payload, the expendable one can reach with a 7.03t payload.

A 5.5t payload is 78% of a 7.03t payload, so the F9 Block 5 loses 22% of its GTO payload when recovering the first stage.

Doesn't match the SpaceX claims of 8.3 tonnes GTO and 22.8 tonnes LEO, which date back to the start of Block 5 I think.  Maybe they gave up payload to beef up the fairings for sea recovery?

 - Ed Kyle

I suspect SpaceX is still reserving performance for engine-out. The max payload figures probably assume burn to depletion as well (less accurate).

It might also include staging the fairing off early (like with Starlink) and using a non-recoverable fairing as you also speculate.

[LouScheffer]

With this flight we can re-calibrate the loss of payload for recoverability.  This flight staged at 9777 km/hr = 2715 m/s.  The preceding G33/G34 flight (with recovery) staged at 8340 km/hr = 2316 m/s.   Thus the first stage provided roughly 400 m/s more (roughly because the differing payload masses will have some small effect on first stage dV).

Now making the usual second stage assumptions (fuel = 107t, empty mass + residual = 5.5t, ISP = 348), then how much can you increase the payload from the nominal 5.5t if the second stage needs to produce 400 m/s less?  Turns out it's 7.03t.  So any orbit the recoverable rocket can reach with a 5.5t payload, the expendable one can reach with a 7.03t payload.

A 5.5t payload is 78% of a 7.03t payload, so the F9 Block 5 loses 22% of its GTO payload when recovering the first stage.

Doesn't match the SpaceX claims of 8.3 tonnes GTO and 22.8 tonnes LEO, which date back to the start of Block 5 I think.  Maybe they gave up payload to beef up the fairings for sea recovery?

These are not maximums - they are just equivalences.  I just picked typical payload masses near the high end of the range for recoverable missions (but not at the limit, which I don't know) and found the payload that an expendable could put into exactly the same orbit.  The objective was to compute the ratio, not the limit.

[litton4]

This means that all components of the Demo-1 mission now no longer exist (apart from, maybe, Ripley).
Capsule was destroyed in a Super Draco test.
Second stage always expended
Booster now RIP.

[mn]

With this flight we can re-calibrate the loss of payload for recoverability.  This flight staged at 9777 km/hr = 2715 m/s.  The preceding G33/G34 flight (with recovery) staged at 8340 km/hr = 2316 m/s.   Thus the first stage provided roughly 400 m/s more (roughly because the differing payload masses will have some small effect on first stage dV).

Now making the usual second stage assumptions (fuel = 107t, empty mass + residual = 5.5t, ISP = 348), then how much can you increase the payload from the nominal 5.5t if the second stage needs to produce 400 m/s less?  Turns out it's 7.03t.  So any orbit the recoverable rocket can reach with a 5.5t payload, the expendable one can reach with a 7.03t payload.

A 5.5t payload is 78% of a 7.03t payload, so the F9 Block 5 loses 22% of its GTO payload when recovering the first stage.

Doesn't match the SpaceX claims of 8.3 tonnes GTO and 22.8 tonnes LEO, which date back to the start of Block 5 I think.  Maybe they gave up payload to beef up the fairings for sea recovery?

 - Ed Kyle

Doesn't GTO come in many flavors?

How does this mission compare to the minimum that can be called GTO?

[Alexphysics]

Well in terms of expendable F9, this mission performed better than the last time they tried the same. For reference, Amos 17 went into a GTO-1784 vs GTO-1611 achieved on this launch. Would be interesting to compare the telemetry from both missions... *wink wink* https://twitter.com/Alexphysics13/status/1591560891128254465

[smoliarm]

With this flight we can re-calibrate the loss of payload for recoverability.  This flight staged at 9777 km/hr = 2715 m/s.  The preceding G33/G34 flight (with recovery) staged at 8340 km/hr = 2316 m/s.   Thus the first stage provided roughly 400 m/s more (roughly because the differing payload masses will have some small effect on first stage dV).

Now making the usual second stage assumptions (fuel = 107t, empty mass + residual = 5.5t, ISP = 348), then how much can you increase the payload from the nominal 5.5t if the second stage needs to produce 400 m/s less?  Turns out it's 7.03t.  So any orbit the recoverable rocket can reach with a 5.5t payload, the expendable one can reach with a 7.03t payload.

A 5.5t payload is 78% of a 7.03t payload, so the F9 Block 5 loses 22% of its GTO payload when recovering the first stage.

Doesn't match the SpaceX claims of 8.3 tonnes GTO and 22.8 tonnes LEO, which date back to the start of Block 5 I think.  Maybe they gave up payload to beef up the fairings for sea recovery?

 - Ed Kyle

of course it does not match - these are different GTOs:
The original claim by SpaceX - "8.3 t to GTO" - implies GTO(-1800 m/s)
In this flight the payload was delivered to substantially *higher* GTO ~ -1600 m/s

[Tomness]

With this flight we can re-calibrate the loss of payload for recoverability.  This flight staged at 9777 km/hr = 2715 m/s.  The preceding G33/G34 flight (with recovery) staged at 8340 km/hr = 2316 m/s.   Thus the first stage provided roughly 400 m/s more (roughly because the differing payload masses will have some small effect on first stage dV).

Now making the usual second stage assumptions (fuel = 107t, empty mass + residual = 5.5t, ISP = 348), then how much can you increase the payload from the nominal 5.5t if the second stage needs to produce 400 m/s less?  Turns out it's 7.03t.  So any orbit the recoverable rocket can reach with a 5.5t payload, the expendable one can reach with a 7.03t payload.

A 5.5t payload is 78% of a 7.03t payload, so the F9 Block 5 loses 22% of its GTO payload when recovering the first stage.

Doesn't match the SpaceX claims of 8.3 tonnes GTO and 22.8 tonnes LEO, which date back to the start of Block 5 I think.  Maybe they gave up payload to beef up the fairings for sea recovery?

 - Ed Kyle

of course it does not match - these are different GTOs:
The original claim by SpaceX - "8.3 t to GTO" - implies GTO(-1800 m/s)
In this flight the payload was delivered to substantially *higher* GTO ~ -1600 m/s

That gets close to GTO-1500 from French Guiana

[OneSpeed]

Well in terms of expendable F9, this mission performed better than the last time they tried the same. For reference, Amos 17 went into a GTO-1784 vs GTO-1611 achieved on this launch. Would be interesting to compare the telemetry from both missions... *wink wink*

The payloads for AMOS-17 and G31-32 were the same, at 6,500kg. The AMOS-17 booster profile was unusual because there was no throttle up after MaxQ, and so gravity losses would have been a little higher. MECOs were at 2644 and 2716m/s respectively.

Second stage burn times:

Mission	LEO s	GTO s
AMOS-17	315	61
G31-32	308	71

So, the G31-32 second stage burn to LEO was 7s shorter, and her (lower throttle) burn to GTO was 10s longer.

[Josh_from_Canada]

That gets close to GTO-1500 from French Guiana

Makes sense as there's another two nearly identical satellites going up on VA259

[Comga]

Well in terms of expendable F9, this mission performed better than the last time they tried the same. For reference, Amos 17 went into a GTO-1784 vs GTO-1611 achieved on this launch. Would be interesting to compare the telemetry from both missions... *wink wink*

The payloads for AMOS-17 and G31-32 were the same, at 6,500kg. The AMOS-17 booster profile was unusual because there was no throttle up after MaxQ, and so gravity losses would have been a little higher. MECOs were at 2644 and 2716m/s respectively.

Second stage burn times:

Mission	LEO s	GTO s
AMOS-17	315	61
G31-32	308	71

So, the G31-32 second stage burn to LEO was 7s shorter, and her (lower throttle) burn to GTO was 10s longer.

Thank you, as always, for so much data on which to chew.

I have a question:
Why would the second burn of the G31-32 second stage be so delayed when compared to that for AMOS-17?
The general principle is that this burn should occur over the equator.
However, as the downrange distances as functions of time are equal, to the resolution of the graph, a difference in timing would equate to a difference in downrange distance, longitude, and, most significantly, lattitude.
Is there a detail in the data that I am missing that allows both to be over the Equator?
If not, why would this be chosen when it appears to be other than optimal?

[ZachS09]

Well in terms of expendable F9, this mission performed better than the last time they tried the same. For reference, Amos 17 went into a GTO-1784 vs GTO-1611 achieved on this launch. Would be interesting to compare the telemetry from both missions... *wink wink*

The payloads for AMOS-17 and G31-32 were the same, at 6,500kg. The AMOS-17 booster profile was unusual because there was no throttle up after MaxQ, and so gravity losses would have been a little higher. MECOs were at 2644 and 2716m/s respectively.

Second stage burn times:

Mission	LEO s	GTO s
AMOS-17	315	61
G31-32	308	71

So, the G31-32 second stage burn to LEO was 7s shorter, and her (lower throttle) burn to GTO was 10s longer.

I thought Galaxy 31/Galaxy 32 weighed 6.6 tons.

[OneSpeed]

I have a question:
Why would the second burn of the G31-32 second stage be so delayed when compared to that for AMOS-17?
The general principle is that this burn should occur over the equator.
However, as the dosnrange distances are equal to the resolution of the graph, a difference in timing would equate to a difference in downrange distance, longitude, and, most significantly, lattitude.
Is there a detail in the data that I am missing that allows both to be over the Equator?
If not, why would this be chosen when it appears to be other than optimal?

Another parameter that can be tweaked is launch azimuth. Attached is an anigif of the launch hazard areas for AMOS-17 and Galaxy 31-32, showing that AMOS-17 launched further North (open the anigif to see the animation).

From the webcasts, AMOS-17 flew a little South of the ground tracking station at Libreville (0.39° N), reaching the equator 25s earlier than G31-32. Meanwhile, G31-32 crossed the equator and began its GTO burn some 200km further downrange.

Edit: reworked the anigif from the original NGA co-ordinates, just to be sure.

I thought Galaxy 31/Galaxy 32 weighed 6.6 tons.

Wikipedia had ~6,500 kg listed when I posted, it now shows ~6,600 kg.

[Comga]

That is true but raises two issues:

Launching at any azimuth other than due east increases the inclination of the initial orbit, which would increase the plane change to GEO.  This in turn increases the delta-V deficit to GEO, which mostly falls on the spacecraft burn at apogee.  That would make it less efficient.

Also, if Galaxy 31&32 launch in a more southerly direction, their trajectory would get to the Equator earlier, not later.

Now there are TWO things I don’t understand!
(I feel like The Cat In The Hat with the red spots!)

PS That’s a really neat “anigif” of the hazard zones.

[litton4]

Please can someone remind me (or point at an explanation) of what the GTO-xxxx numbers mean?

[LouScheffer]

Please can someone remind me (or point at an explanation) of what the GTO-xxxx numbers mean?

Sure, the XXXX is the number of m/s left to get into geosynchronous orbit, so smaller numbers are better.   It's a combination of two tasks  - to circularize the orbit at geosynchronous height, and to remove any remaining inclination from the transfer orbit.  As an example, a GTO with a GEO apogee from the Cape is about GTO-1800, whereas a GTO with GEO apogee from French Guiana is typically about GTO-1500, since the spacecraft has less inclination to remove.

If your rocket has more dV than needed to simply reach GTO apogee, you can spend it by increasing the apogee above geosynchronous (which makes the plane change cheaper, by reducing the inclination cost), or reducing the inclination of the transfer orbit.

[ZachS09]

Please can someone remind me (or point at an explanation) of what the GTO-xxxx numbers mean?

Sure, the XXXX is the number of m/s left to get into geosynchronous orbit, so smaller numbers are better.   It's a combination of two tasks  - to circularize the orbit at geosynchronous height, and to remove any remaining inclination from the transfer orbit.  As an example, a GTO with a GEO apogee from the Cape is about GTO-1800, whereas a GTO with GEO apogee from French Guiana is typically about GTO-1500, since the spacecraft has less inclination to remove.

If your rocket has more dV than needed to simply reach GTO apogee, you can spend it by increasing the apogee above geosynchronous (which makes the plane change cheaper, by reducing the inclination cost), or reducing the inclination of the transfer orbit.

Also, you can use the spare delta-v to raise the perigee significantly and reduce the inclination a bit more at apogee.

[tbellman]

Please can someone remind me (or point at an explanation) of what the GTO-xxxx numbers mean?

Sure, the XXXX is the number of m/s left to get into geosynchronous orbit, so smaller numbers are better.   It's a combination of two tasks  - to circularize the orbit at geosynchronous height, and to remove any remaining inclination from the transfer orbit.  As an example, a GTO with a GEO apogee from the Cape is about GTO-1800, whereas a GTO with GEO apogee from French Guiana is typically about GTO-1500, since the spacecraft has less inclination to remove.

It's more commonly, and more appropriately in my opinion, written as GEO-1500, as in "GEO(stationary orbit) minus 1500 (m/s)".  "GTO-1500" sounds like it would be 1500 m/s shy of the elliptical transfer orbit (with perigee at a couple hundred kilometers and apogee at ~36000 km), instead of 1500 m/s shy of the actual circular geostationary orbit.  Nitpicking, I know, but that allows you to generalize it and say things like "TLI-100" (trans-lunar injection minus 100).

On another note, it can be worth mentioning that one way of lowering the amount of Δv needed by the satellite to enter GEO, is to insert it into an orbit with apogee higher than 36000 km; this is called a super-synchronous transfer orbit.  Since the velocity at the apogee is then lower, you need less energy to change the inclination.  And this is what was done in this particular launch, putting the apogee at 38000 km.  (Another way is of course to raise the perigee of the transfer orbit instead, so the satellite will need less energy to circularize.  That however means that the upper stage of the launch rocket will need to reserve some propellant to lower its perigee again afterwards, so it can deorbit in a reasonable time.)

[jcm]

Still only 2 objects cataloged from the launch (although there is currently a gap, 54245, which could be the third object).

It seems unlikely that the second stage was deorbited given the performance concerns, so I assume the third object will eventually show up.

[LouScheffer]

Still only 2 objects cataloged from the launch (although there is currently a gap, 54245, which could be the third object).

It seems unlikely that the second stage was deorbited given the performance concerns, so I assume the third object will eventually show up.

Also, the two that are there have quite different inclinations (24.2 and 22.3), if I'm reading the elements right.  This seems odd - I can't see any reason to change the inclination without changing the perigee.  It's quite a bit less efficient than combining the maneuvers.  So something is odd....

[FutureSpaceTourist]

https://twitter.com/spaceoffshore/status/1592289546330574848

Bob is due to arrive at Port Canaveral at midnight tonight with the fairing from Galaxy 31 & 32.