I don't know anything about the current mission
I'll try and be helpful. Intelsat 35e was a nominal mission with greater than expected performance. OA-6 experienced an anomaly greatly impacting performance, but was able to (barely) achieve mission success due to excess performance being available.
In the future, I would suggest that commenting on something you admit you don't have any knowledge of ends up harming the content of your post. woods170 is correct, and your analogy is invalid.
Sorry if you missed my point, I was NOT COMMENTING on the current mission.
I am not comparing the first stage performance of these two missions and I am NOT suggesting in any way shape or form that there was an anomaly here - I think you are reading extra thoughts into my post.
I was only commenting on the statement that I quoted, it's just silly logic (I'm discussing logic - not engineering, I'm not an engineer) (in my opinion) to say "the first stage performance doesn't matter as long as the payload made it to the expected orbit". that is the only part I was commenting on and I think the analogy to OA-6 is perfectly valid.
feel free to think different.
Sorry if you missed my point, I was NOT COMMENTING on the current mission.
In case you didn't notice, we're in the current mission thread. And you are commenting on a comment that is related to this mission. And you previously said and I quote "I don't know anything about the current mission". But you're going to compare it to another mission anyway?
Anyway, if you're going to paraphrase someone, you should make sure you do it correctly.
"the first stage performance doesn't matter as long as the payload made it to the expected orbit"
versus
That said, first stage performance in this case does not matter. It's the final performance at payload separation that counts. And that was well above expectation.
Your comparison is invalid and your conclusion is wrong. To avoid anything more snarky, I'll stop there.
Sorry if you missed my point, I was NOT COMMENTING on the current mission.
In case you didn't notice, we're in the current mission thread. And you are commenting on a comment that is related to this mission. And you previously said and I quote "I don't know anything about the current mission". But you're going to compare it to another mission anyway?
Anyway, if you're going to paraphrase someone, you should make sure you do it correctly.
"the first stage performance doesn't matter as long as the payload made it to the expected orbit"
versusThat said, first stage performance in this case does not matter. It's the final performance at payload separation that counts. And that was well above expectation.
Your comparison is invalid and your conclusion is wrong. To avoid anything more snarky, I'll stop there.
Whoa I missed the words "in this case", I stand corrected, thank you
Did anybody else notice that the first stage shut down two seconds earlier than during the Inmarsat-5 mission? Staging also occured 3km lower and about 80m/s slower. So unless SpaceX put 4 tons less fuel into the stage, something didn't quite go as planned.
I noticed that it was two seconds longer than the number given in the press kit. I have it as about one second shorter than during the Inmarsat launch. Throttling differences possibly account for much of the difference. These are the two longest first stage burns by any v1.2 variant.
Here are my notes:
Inmarsat 5 F4: S1 165 sec, S2-1 342 sec, S2-2 56 sec
Intelsat 35e: S1 164 sec, S2-1 346 sec, S2-2 57 sec
Intelsat 35e Presskit: S1 162 sec, S2-1 344 sec, S2-2 52 sec
- Ed Kyle
Is the difference due to expected performance (with margins) vs. actual performance (minimum residuals)?
By my numbers, the difference between a 28,000 km Ap and a 43,000 km Ap from Intelsat-35e's parking orbit is approximately 256 m/s at perigee, which is a very small margin if you think about it.
By my numbers, the difference between a 28,000 km Ap and a 43,000 km Ap from Intelsat-35e's parking orbit is approximately 256 m/s at perigee, which is a very small margin if you think about it.
It's about 2% of total dV
By my numbers, the difference between a 28,000 km Ap and a 43,000 km Ap from Intelsat-35e's parking orbit is approximately 256 m/s at perigee, which is a very small margin if you think about it.
That's about 5 years of service life (orbit maintenance propellant) if previous posts here are accurate.
Doesn't sound small to me.
Did anybody else notice that the first stage shut down two seconds earlier than during the Inmarsat-5 mission? Staging also occured 3km lower and about 80m/s slower. So unless SpaceX put 4 tons less fuel into the stage, something didn't quite go as planned.
I noticed that it was two seconds longer than the number given in the press kit. I have it as about one second shorter than during the Inmarsat launch. Throttling differences possibly account for much of the difference. These are the two longest first stage burns by any v1.2 variant.
Here are my notes:
Inmarsat 5 F4: S1 165 sec, S2-1 342 sec, S2-2 56 sec
Intelsat 35e: S1 164 sec, S2-1 346 sec, S2-2 57 sec
Intelsat 35e Presskit: S1 162 sec, S2-1 344 sec, S2-2 52 sec
- Ed Kyle
Is the difference due to expected performance (with margins) vs. actual performance (minimum residuals)?
I take the press kits as a vague, rough outline, not as a definitive timeline. They almost always differ from the actual mission by a few seconds at least. As for the differences between the Inmarsat and Intelsat flights, I think they can be accounted for in payload mass, orbit, and throttle variations.
- Ed Kyle
By my numbers, the difference between a 28,000 km Ap and a 43,000 km Ap from Intelsat-35e's parking orbit is approximately 256 m/s at perigee, which is a very small margin if you think about it.
It's about 2% of total dV
But if they are throttling the engine to stay at 5 g's, that's ~5 seconds, which represents ~10% longer second stage burn.
Check out this long distance footage of the launch, by far the best view I ever saw of exhaust recirculation along the F9 at around 1:30 min into the video. Looks like it creeps up even further along the rocket than what Saturn V experienced.
How would these numbers look if you went by payload mass rather than number of flights? Counting the Orbiter as part of the LV for this purpose. Are SpaceX beating the payload to orbit achieved by the shuttle and ELVs?
For 1985, when STS flew 9 times, the numbers are close, but STS appears to have slightly exceeded Falcon 9's payload numbers for its 10 flights in 2017 to date.
In 1985, STS put 14 satellites into GTO or GEO using IUS, PAM-D, PAM-D2, or other PKMs. My estimate of the total satellite or equivalent satellite mass placed into GTO in 1985 is about 27.5 tonnes (just for the satellites, not the PKMs). Falcon 9 has boosted about 27.4 tonnes to GTO in five missions so far this year.
In 1985, STS lifted about 43.9 tonnes to LEO, including three Spacelabs, Spartan-101, and a handful of other payloads. So far this year, Falcon 9 has lifted about 36.63 tonnes in five LEO missions, assuming that the NROL-76 payload was relatively light. Of note, however, is that two of the Falcon 9 missions have gone to near-polar orbit from VAFB, something Shuttle never achieved. The other Falcon 9 LEO flights have gone to 51.6 deg orbits, something STS didn't do in 1985.
Of course STS also put 58 astronauts into orbit in 1985, something Falcon 9 has yet to achieve, and we haven't accounted for the mass involved in supporting the human flight aspect here.
- Ed Kyle
A thought. Is there some metric per flight that would combine payload x C3 x some compensation for inclination dV during launch?
Cheers, Martin
Did anybody else notice that the first stage shut down two seconds earlier than during the Inmarsat-5 mission? Staging also occured 3km lower and about 80m/s slower. So unless SpaceX put 4 tons less fuel into the stage, something didn't quite go as planned.
It seems this is well within the normal dispersion.
Immarsat put a lighter payload into minimal GTO +377 m/s. Extrapolating to the heavier payload, you would expect the first stage to provide 10 m/s less, and the second 190 m/s less, for a totai of MGTO + 175 (apogee of 48K km). But they got an apogee of 44K km, or MGTO+135, or about 40 m/s less. So the first stage was -70 m/s from expectation and the second stage +30 m/s.
The minimum acceptable orbit was an apogee of 31000 km (from the press) which is about MGTO - 100 m/s. SpaceX would probably quote something like - 3 or -4 sigma for the minimum performance. So I'd guess the standard deviation they expected was something like 50-60 m/s. Assuming the stages are independent, that's a dispersion per stage of 40 m/s or so. In this case the first stage was 1.75 sigma short, but the second stage is 0.75 sigma high, for about a -1 sigma total dispersion. Of course this is assuming the InMarSat mission was completely nominal. It's statistically better to assume that mission was was +1/2 sigma, and this one -1/2 sigma. This makes the stage performance even closer to nominal.
I wonder if any of this was due to the LOX being not quite as cold on the third attempt, due to the two previous drainbacks.
