SpaceX F9 : SES-10 with reuse of CRS-8 Booster SN/1021 : 2017-03-30 : DISCUSSION

[FutureSpaceTourist]

Anyway, is this booster going to be used again?  Maybe for a LEO flight to ISS?

No. Elon said in the press conference after the flight that he plans to offer it to the Cape (presumably for display somewhere, like the first landed booster is at SoaceX in Hawthorne).

[mn]

...Unless you have evidence beyond the TLEs, I'd say there's not reason to imagine that the launch undershot...

Some of us (myself included) are imagining a shortfall based on the announcer's reaction at SC separation, his reaction seemed hesitant as he looked at the screen and finally said the orbit is 'good enough'. (and we all know that 'good enough' is NOT good enough).

Of course that is not evidence, his data might not have been 100% clear and just because he wasn't sure doesn't mean it wasn't as expected.

And finally even after confirming that 'it didn't fall short', doesn't preclude the possibility that they were expecting a bit more.

Anyway just explaining why at least I (and perhaps others) am left wondering.

Edit: removed irrelevant parts of quote.

[meekGee]

...Unless you have evidence beyond the TLEs, I'd say there's not reason to imagine that the launch undershot...

Some of us (myself included) are imagining a shortfall based on the announcer's reaction at SC separation, his reaction seemed hesitant as he looked at the screen and finally said the orbit is 'good enough'. (and we all know that 'good enough' is NOT good enough).

Of course that is not evidence, his data might not have been 100% clear and just because he wasn't sure doesn't mean it wasn't as expected.

And finally even after confirming that 'it didn't fall short', doesn't preclude the possibility that they were expecting a bit more.

Anyway just explaining why at least I (and perhaps others) am left wondering.

Edit: removed irrelevant parts of quote.

"good enough" means under the nominal expected value  but within the allowed range.

If you always exceeded the expected value, then it wouldn't be "expected", it would be "minimal"...

[mn]

...Unless you have evidence beyond the TLEs, I'd say there's not reason to imagine that the launch undershot...

Some of us (myself included) are imagining a shortfall based on the announcer's reaction at SC separation, his reaction seemed hesitant as he looked at the screen and finally said the orbit is 'good enough'. (and we all know that 'good enough' is NOT good enough).

Of course that is not evidence, his data might not have been 100% clear and just because he wasn't sure doesn't mean it wasn't as expected.

And finally even after confirming that 'it didn't fall short', doesn't preclude the possibility that they were expecting a bit more.

Anyway just explaining why at least I (and perhaps others) am left wondering.

Edit: removed irrelevant parts of quote.

"good enough" means under the nominal expected value  but within the allowed range.

If you always exceeded the expected value, then it wouldn't be "expected", it would be "minimal"...

And to my simple mind "under the nominal expected value but within the allowed range" = "undershot" aka "less than expected" aka "something didn't quite work as expected but we still made it". (The range of 'acceptable' values for the launch contract is hopefully wider than the range of 'expected' values).

[meekGee]

...Unless you have evidence beyond the TLEs, I'd say there's not reason to imagine that the launch undershot...

Some of us (myself included) are imagining a shortfall based on the announcer's reaction at SC separation, his reaction seemed hesitant as he looked at the screen and finally said the orbit is 'good enough'. (and we all know that 'good enough' is NOT good enough).

Of course that is not evidence, his data might not have been 100% clear and just because he wasn't sure doesn't mean it wasn't as expected.

And finally even after confirming that 'it didn't fall short', doesn't preclude the possibility that they were expecting a bit more.

Anyway just explaining why at least I (and perhaps others) am left wondering.

Edit: removed irrelevant parts of quote.

"good enough" means under the nominal expected value  but within the allowed range.

If you always exceeded the expected value, then it wouldn't be "expected", it would be "minimal"...

And to my simple mind "under the nominal expected value but within the allowed range" = "undershot" aka "less than expected" aka "something didn't quite work as expected but we still made it". (The range of acceptable values for the launch contract is hopefully wider than the range of 'expected' values).

If you're going to forecast a range, and you say 10 +/- 1, and it comes out as 9.5, did it "underperform"?

That's the nature of expected values - you get a cluster around them, not above them.

[mn]

...Unless you have evidence beyond the TLEs, I'd say there's not reason to imagine that the launch undershot...

Some of us (myself included) are imagining a shortfall based on the announcer's reaction at SC separation, his reaction seemed hesitant as he looked at the screen and finally said the orbit is 'good enough'. (and we all know that 'good enough' is NOT good enough).

Of course that is not evidence, his data might not have been 100% clear and just because he wasn't sure doesn't mean it wasn't as expected.

And finally even after confirming that 'it didn't fall short', doesn't preclude the possibility that they were expecting a bit more.

Anyway just explaining why at least I (and perhaps others) am left wondering.

Edit: removed irrelevant parts of quote.

"good enough" means under the nominal expected value  but within the allowed range.

If you always exceeded the expected value, then it wouldn't be "expected", it would be "minimal"...

And to my simple mind "under the nominal expected value but within the allowed range" = "undershot" aka "less than expected" aka "something didn't quite work as expected but we still made it". (The range of acceptable values for the launch contract is hopefully wider than the range of 'expected' values).

If you're going to forecast a range, and you say 10 +/- 1, and it comes out as 9.5, did it "underperform"?

That's the nature of expected values - you get a cluster around them, not above them.

No I would not consider that to be an underperform.

BUT if the contractual 'acceptable' range is 100 +-6 and the 'expected/forecasted' range is 100+-2 and the result is 95, I would consider that both 'good enough' and 'underperform'.

What actually happened here I don't know.

It didn't "fall short." We have direct word on that in L2.

Just trying to get clarity on that statement: does it mean the original statement of 'good enough' was incorrect? or was it both 'within the acceptable range' and 'less than expected'? (the point I'm trying to make is that these two statements are NOT mutually exclusive, and therefore the result is still unclear to me.)

[meekGee]

...Unless you have evidence beyond the TLEs, I'd say there's not reason to imagine that the launch undershot...

Some of us (myself included) are imagining a shortfall based on the announcer's reaction at SC separation, his reaction seemed hesitant as he looked at the screen and finally said the orbit is 'good enough'. (and we all know that 'good enough' is NOT good enough).

Of course that is not evidence, his data might not have been 100% clear and just because he wasn't sure doesn't mean it wasn't as expected.

And finally even after confirming that 'it didn't fall short', doesn't preclude the possibility that they were expecting a bit more.

Anyway just explaining why at least I (and perhaps others) am left wondering.

Edit: removed irrelevant parts of quote.

"good enough" means under the nominal expected value  but within the allowed range.

If you always exceeded the expected value, then it wouldn't be "expected", it would be "minimal"...

And to my simple mind "under the nominal expected value but within the allowed range" = "undershot" aka "less than expected" aka "something didn't quite work as expected but we still made it". (The range of acceptable values for the launch contract is hopefully wider than the range of 'expected' values).

If you're going to forecast a range, and you say 10 +/- 1, and it comes out as 9.5, did it "underperform"?

That's the nature of expected values - you get a cluster around them, not above them.

No I would not consider that to be an underperform.

BUT if the contractual 'acceptable' range is 100 +-6 and the 'expected/forecasted' range is 100+-2 and the result is 95, I would consider that both 'good enough' and 'underperform'.

What actually happened here I don't know.

It didn't "fall short." We have direct word on that in L2.

Just trying to get clarity on that statement: does it mean the original statement of 'good enough' was incorrect? or was it both 'within the acceptable range' and 'less than expected'? (the point I'm trying to make is that these two statements are NOT mutually exclusive, and therefore the result is still unclear to me.)

They were clear it was the first case.  "Good enough", in the tone used, meant under the nominal value, but within the range.

[mn]

They were clear it was the first case.  "Good enough", in the tone used, meant under the nominal value, but within the range.

Please clarify 'within the expected range' or 'within the acceptable range'

[meekGee]

They were clear it was the first case.  "Good enough", in the tone used, meant under the nominal value, but within the range.

Please clarify 'within the expected range' or 'within the acceptable range'

The customer said "I want at least 9”.

The guidance people said the profile will give 10 (expected value) +/- 0.8 (expected range) and they are 95% confident in that.

SpaceX therefore promised to deliver at least 9.  Anything less then that would be unacceptable and trigger a penalty.

For some values of 9, 10, 0.8, and 95, and using metric percents.

[Herb Schaltegger]

They were clear it was the first case.  "Good enough", in the tone used, meant under the nominal value, but within the range.

Please clarify 'within the expected range' or 'within the acceptable range'

Frankly, what difference does it make? The customer was satisfied, SpaceX was satisfied and unless you work for either of them or their insurance underwriters, you're not likely to ever have the technical insight into specifics to know one way or the other.

[ChrisC]

Here's Jeff Foust's write-up of Gwynne's remarks today:

http://spacenews.com/spacex-gaining-substantial-cost-savings-from-reused-falcon-9/

Oh my god, this is the best quote ever:

Shotwell said she believed an industry skeptical of SpaceX’s efforts to reuse Falcon 9 boosters had become convinced it would be useful. She recalled a quote from science fiction author Arthur C. Clarke describing the three stages of reactions to revolutionary ideas. “‘It’s completely impossible.’ We’ve heard that for 15 years. ‘It’s possible, but not worth doing.’ We’re still hearing that a little bit,” she said.”

“But,” she added, “we’re also starting to hear, ‘I said it was a good idea all along.’”

(That's the second quote on this ACC page)

[mn]

They were clear it was the first case.  "Good enough", in the tone used, meant under the nominal value, but within the range.

Please clarify 'within the expected range' or 'within the acceptable range'

Frankly, what difference does it make? The customer was satisfied, SpaceX was satisfied and unless you work for either of them or their insurance underwriters, you're not likely to ever have the technical insight into specifics to know one way or the other.

Seems to me there's a big difference between the two, but I guess I'm the only one. So forget I asked, let's move on.

[pb2000]

They were clear it was the first case.  "Good enough", in the tone used, meant under the nominal value, but within the range.

Please clarify 'within the expected range' or 'within the acceptable range'

Frankly, what difference does it make? The customer was satisfied, SpaceX was satisfied and unless you work for either of them or their insurance underwriters, you're not likely to ever have the technical insight into specifics to know one way or the other.

Seems to me there's a big difference between the two, but I guess I'm the only one. So forget I asked, let's move on.

At the rate SpaceX is changing the industry, I wouldn't be surprised if they take a stab at orbital refueling long before SES looks at the gas tanks and wishes it had that extra bit of deltaV on launch.

[Herb Schaltegger]

They were clear it was the first case.  "Good enough", in the tone used, meant under the nominal value, but within the range.

Please clarify 'within the expected range' or 'within the acceptable range'

Frankly, what difference does it make? The customer was satisfied, SpaceX was satisfied and unless you work for either of them or their insurance underwriters, you're not likely to ever have the technical insight into specifics to know one way or the other.

Seems to me there's a big difference between the two, but I guess I'm the only one. So forget I asked, let's move on.

There is a difference but in the context of discussion here, with this audience and in consideration of the reality that no one here knows the answer, it's "a distinction that makes no difference."

By and large, modern comsats regularly exceed their nominal 15 year orbital lifespans. Provided SpaceX met their contractual requirements for "GTO-xxxxx m/s" (and we don't know that contractual number), ultimately that's all that matters. We space nerds may want to argue about it, and we may over-analyze a very off-the-cuff "Good enough!" remark made in a moment of excitement on a live webcast, but the net result is very much like theologians arguing about the area of the head of a pin divided by the average area of an angel's derriere ...

[Jcc]

Correct me if I'm wrong, but there are reasons why performance on a mission could be slightly lower or higher than expected that have nothing to do with the performance of the engines, namely, the direction and strength of the wind during launch. Seems to me I recall better than expected performance that was attributed to the winds being favorable.

[sewebster]

It seems to me that there is probably enough knowledge on this site and/or ability to do some math, to determine some plausible ranges for both:
(a) contract requirements in terms of acceptable deviation from desired orbit
(b) distribution of deviations from target orbit for nominal flights.

Depending on how similar or not those ranges are could have a bearing on how interesting it would be to hear things like "good enough."

But this sounds very general and therefore if I were going to discuss it further I would start a new thread.

[JamesH65]

It seems to me that there is probably enough knowledge on this site and/or ability to do some math, to determine some plausible ranges for both:
(a) contract requirements in terms of acceptable deviation from desired orbit
(b) distribution of deviations from target orbit for nominal flights.

Depending on how similar or not those ranges are could have a bearing on how interesting it would be to hear things like "good enough."

But this sounds very general and therefore if I were going to discuss it further I would start a new thread.

Is it just me, or is this whole argument utterly pointless? The satellite is in an orbit which is correct, and the satellite owners are happy.

What on earth is there to argue about?

Correct means within the range of acceptable orbits. There is no argument - if it is in the range, it is in the correct orbit, because anything in that range is the correct orbit. There is no 'slightly more correct' or 'slightly less correct'.

[Kaputnik]

It seems to me that there is probably enough knowledge on this site and/or ability to do some math, to determine some plausible ranges for both:
(a) contract requirements in terms of acceptable deviation from desired orbit
(b) distribution of deviations from target orbit for nominal flights.

Depending on how similar or not those ranges are could have a bearing on how interesting it would be to hear things like "good enough."

But this sounds very general and therefore if I were going to discuss it further I would start a new thread.

Is it just me, or is this whole argument utterly pointless? The satellite is in an orbit which is correct, and the satellite owners are happy.

What on earth is there to argue about?

Correct means within the range of acceptable orbits. There is no argument - if it is in the range, it is in the correct orbit, because anything in that range is the correct orbit. There is no 'slightly more correct' or 'slightly less correct'.

If the payload was delivered to slightly under the exact desired orbit, and if the normal operation of the vehicle would allow a more accurate insertion, then it can be assumed that this was a burn-to-depletion insertion.

And if this was a burn-to-depletion insertion, then it gives a useful insight into the actual real world performance of the F9 system.

So there may be some merit in discussing this.

[Lar]

... But not on this thread, I think. SEWebster is right, we probably could analyse this quite a bit and get some useful info. In a new thread.

PS I don't think anyone is arguing.... well sort of.

[BabaORileyUSA]

The values you are showing for the SES-10 are after a velocity augmentation maneuver.  The apogee height of Elset One was 33,460 km, about 1,200 km lower than what you are showing.

I'm using the oldest TLE listed at Space-Track, Epoch Fri Mar 31 2017 13:57:30 GMT, 14 or 15 hours after launch so time enough for one complete orbit.

 - Ed Kyle

Isn't it odd that the stage is now at a 240 km perigee, over 20 km higher than the first TLE?

The Stage 2 has the lower apogee height, but the earliest elset for the payload has the higher one.
Yes, it's possible there was a PVA burn, but much more likely there was a Stage 2 CCAM/depletion burn which lowered its apogee from an initial one that was the same as the payload. Unless you have evidence beyond the TLEs, I'd say there's not reason to imagine that the launch undershot.

Both a payload PVA and a second stage CCAM/depletion burn occurred.   The apogee height I reported was from 18SPCS Elset One (JSpOC no longer has that responsibility), which was prior to the completion of the first Rev, where the PVA burn occurred.