Author Topic: SpaceX Falcon 9 : CRS-12 : Aug 14, 2017 : DISCUSSION  (Read 74902 times)

Offline FutureSpaceTourist

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Fun video by Scott Manley



Quote
Published on 16 Aug 2017
SpaceX launches Dragon Spacecraft to the International Space Station under the Commercial Resupply Services (CRS) program.
This video synchronizes the launches of CRS-1 through CRS-12 and you can see how the technology and launch profiles have changed.
The were a few Dragon missions prior to this which were technology demonstrators for the Commercial Orbital Transportation Services (COTS) program, the second of which berthed at the ISS in May 2012. This is missing from the video because 13 is not a convenient number for this presentation :)

Mission control audio is chopped up with sections from all launches intermixed to highlight the major events.

The music is by Test Shot Starfish who do all the music for the SpaceX livestreams.
https://soundcloud.com/testshotstarfish
Tracks are 'Re - Flight', 'Approaching Dragon' and 'Andromeda'
https://soundcloud.com/testshotstarfi...
https://soundcloud.com/testshotstarfi...
https://soundcloud.com/testshotstarfi...

Offline Raul

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If there was a thrust increase on the first stage it was so slight as to not be noticeable. There are some really good telemetry graphs and two comparisons between CRS-11 and CRS-12 that can be found on this reddit post. Its quite obvious that, everything else being relatively equal, both CRS-11 and CRS-12 were flown with basically the same thrust (but different max-q throttling).

I'm very curious what was meant by the above quote. Did it just mean that the flown engines were uprated but flown at same thrust levels?

It could be also possible that increased booster liftoff thrust upto 7.6MN (1.71M lbf) was used already before this first flight of Block 4 booster (incl. CRS-11), as it was mentioned first time by John Federspiel during NROL-76 webcast (also S2 in Block 4 configuration for the first time), mentioned that similarly also during BulgariaSat-1 webcast, or by SFN in case of Intelsat 35e. Could be only tweaked thrust without fundamental HW changes.
« Last Edit: 08/17/2017 08:19 AM by Raul »

Online Comga

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Fun video by Scott Manley



Quote
Published on 16 Aug 2017
SpaceX launches Dragon Spacecraft to the International Space Station under the Commercial Resupply Services (CRS) program.
This video synchronizes the launches of CRS-1 through CRS-12 and you can see how the technology and launch profiles have changed.
The were a few Dragon missions prior to this which were technology demonstrators for the Commercial Orbital Transportation Services (COTS) program, the second of which berthed at the ISS in May 2012. This is missing from the video because 13 is not a convenient number for this presentation :)

Mission control audio is chopped up with sections from all launches intermixed to highlight the major events.

The music is by Test Shot Starfish who do all the music for the SpaceX livestreams.
https://soundcloud.com/testshotstarfish
Tracks are 'Re - Flight', 'Approaching Dragon' and 'Andromeda'
https://soundcloud.com/testshotstarfi...
https://soundcloud.com/testshotstarfi...
https://soundcloud.com/testshotstarfi...

This is TERRIFIC!
Such an education
The first stage landings have stopped getting faster.  CRS-11 first stage landed at 7:40 elapsed time.  CRS-12 was 6 seconds slower.  CRS9 and CRS-10 were identically 40 seconds slower and CRS-8, going to the ASDS was a full 60 seconds slower.  But they were all exciting to watch, especially together.
There is even more contrast in the first stage flights, with CRS-1 taking way longer to stage.  Yet CRS-5 was the shortest time to separation of Dragon.
Then there are the LOX-cam views. I miss those.
Again, a really cool compilation.
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline quagmire

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This is TERRIFIC!
Such an education
The first stage landings have stopped getting faster.  CRS-11 first stage landed at 7:40 elapsed time.  CRS-12 was 6 seconds slower.  CRS9 and CRS-10 were identically 40 seconds slower and CRS-8, going to the ASDS was a full 60 seconds slower.  But they were all exciting to watch, especially together.
There is even more contrast in the first stage flights, with CRS-1 taking way longer to stage.  Yet CRS-5 was the shortest time to separation of Dragon.
Then there are the LOX-cam views. I miss those.
Again, a really cool compilation.

Do have to keep in mind the reason for the longer staging of CRS-1 was due to compensating for the loss of an engine during ascent so stage 1 did burn longer then planned.

But yes it is a great comparison to how Falcon 9 has changed from 1.0 to todays 1.2B3/4.

Offline rpapo

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Do have to keep in mind the reason for the longer staging of CRS-1 was due to compensating for the loss of an engine during ascent so stage 1 did burn longer then planned.
That's not all.  IIRC, one of the changes to the Falcon 9 1.1+ design was to reduce the first stage portion of the flight relative to the second stage portion so as to make recovery of the first stage easier.
« Last Edit: 08/17/2017 06:13 PM by rpapo »
An Apollo fanboy . . . fifty years ago.

Offline quagmire

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Do have to keep in mind the reason for the longer staging of CRS-1 was due to compensating for the loss of an engine during ascent so stage 1 did burn longer then planned.
That's not all.  IIRC, one of the changes to the Falcon 9 1.1+ design was to reduce the first stage portion of the flight relative to the second stage portion so as to make recovery of the first stage easier.

Right. Was just referencing why CRS-1 staged later even compared to CRS-2 which was also a 1.0.

Offline LouScheffer

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We can estimate the liftoff thrust from the videos.

At the turn of the clock from 6 to 7, it's going 53 km/hr on CR-11 and 51 km/hr on CRS-12.  Assume 52 km/hr which is 14.44 m/s.  Over 7 seconds this is 2.06 m/s^2.

Next we need the mass.  From this Environmental Impact Statement we know the Falcon Full Thrust first stage has about 420 tonnes of fuel.  It's known to mass about 30 tonnes, plus Musk has stated the first stage can push 125 tonnes.  So a total of 575 tonnes at liftoff.

So now takeoff thrust is 575,000 * (9.8 + 2.06) = 6.82 MN = 1.53 million pounds force.  That's exactly the takeoff thrust quoted in the Environmental Impact above, so it's consistent.

So we have definitely not seen the 1.7 million pounds-force version yet.

Offline FutureSpaceTourist

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My apologies, when I saw Scott's video on YouTube I hadn't spotted that a thread for it was already in the SpaceX general section: http://forum.nasaspaceflight.com/index.php?topic=43588.0

Best continue any further discussion there.

Offline deruch

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We can estimate the liftoff thrust from the videos.

At the turn of the clock from 6 to 7, it's going 53 km/hr on CR-11 and 51 km/hr on CRS-12.  Assume 52 km/hr which is 14.44 m/s.  Over 7 seconds this is 2.06 m/s^2.

Next we need the mass.  From this Environmental Impact Statement we know the Falcon Full Thrust first stage has about 420 tonnes of fuel.  It's known to mass about 30 tonnes, plus Musk has stated the first stage can push 125 tonnes.  So a total of 575 tonnes at liftoff.

So now takeoff thrust is 575,000 * (9.8 + 2.06) = 6.82 MN = 1.53 million pounds force.  That's exactly the takeoff thrust quoted in the Environmental Impact above, so it's consistent.

So we have definitely not seen the 1.7 million pounds-force version yet.
Nice analysis.  May have been the 1.7Mlb-f version just flown below the new maximum thrust level though.  Not necessarily inconsistent to have info saying that CRS-12 flew with up-rated engines and data showing that the launch didn't, assuming the higher maximum, use full thrust. 
« Last Edit: 08/18/2017 07:02 AM by deruch »
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Offline LouScheffer

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May have been the 1.7Mlb-f version just flown below the new maximum thrust level though.  Not necessarily inconsistent to have info saying that CRS-12 flew with up-rated engines and data showing that the launch didn't, assuming the higher maximum, use full thrust. 

This makes sense to me, especially for a Dragon mission.  The maximum performance they can use is putting the Dragon into the desired orbit while returning the booster to the Cape.  So engineering would sensibly select the minimum stress profile that achieves this - lower thrust on launch, longer throttle back around Max-Q (which they also did) and so on.  Commercial airplanes do this routinely - if the runway is long enough, they don't use maximum thrust for takeoff.

By not maxing out the rocket,  you could have (numbers for example purposes only) 30% margins on GTO flights, but 40% margins on Dragon flights.  If I were NASA, it would be super appealing for crewed flights to have settings and structural loads well below what has been demonstrated on the test stand and in other (non-crewed) flights.  And doing this now with un-crewed Dragons seems like excellent preparation for doing the same with a crew onboard.

Offline woods170

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We can estimate the liftoff thrust from the videos.

At the turn of the clock from 6 to 7, it's going 53 km/hr on CR-11 and 51 km/hr on CRS-12.  Assume 52 km/hr which is 14.44 m/s.  Over 7 seconds this is 2.06 m/s^2.

Next we need the mass.  From this Environmental Impact Statement we know the Falcon Full Thrust first stage has about 420 tonnes of fuel.  It's known to mass about 30 tonnes, plus Musk has stated the first stage can push 125 tonnes.  So a total of 575 tonnes at liftoff.

So now takeoff thrust is 575,000 * (9.8 + 2.06) = 6.82 MN = 1.53 million pounds force.  That's exactly the takeoff thrust quoted in the Environmental Impact above, so it's consistent.

So we have definitely not seen the 1.7 million pounds-force version yet.
Nice analysis.  May have been the 1.7Mlb-f version just flown below the new maximum thrust level though.  Not necessarily inconsistent to have info saying that CRS-12 flew with up-rated engines and data showing that the launch didn't, assuming the higher maximum, use full thrust. 
You don't fly higher-thrust engines for the first time if you do not intend to utilize that higher thrust.

Offline LouScheffer

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  May have been the 1.7Mlb-f version just flown below the new maximum thrust level though.  Not necessarily inconsistent to have info saying that CRS-12 flew with up-rated engines and data showing that the launch didn't, assuming the higher maximum, use full thrust. 
You don't fly higher-thrust engines for the first time if you do not intend to utilize that higher thrust.
This is not obvious to me.  At some point you start qualifying your engines to a new, higher, maximum thrust.  You incorporate the new engines into new boosters as they are built.   Now suppose the first mission for the new booster does not require the new maximum thrust.   What are you going to do?   Use the new maximum thrust just because you can?  That seems wrong, running at higher ratings surely increases the risk.  Swap if for a booster with crappier engines?  That seems wrong too.

I believe the Shuttle had engine settings which were developed, and qualified, but never intended to be used.  They were reserved for abort scenarios.

Offline woods170

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  May have been the 1.7Mlb-f version just flown below the new maximum thrust level though.  Not necessarily inconsistent to have info saying that CRS-12 flew with up-rated engines and data showing that the launch didn't, assuming the higher maximum, use full thrust. 
You don't fly higher-thrust engines for the first time if you do not intend to utilize that higher thrust.
This is not obvious to me.  At some point you start qualifying your engines to a new, higher, maximum thrust.  You incorporate the new engines into new boosters as they are built.   Now suppose the first mission for the new booster does not require the new maximum thrust.   What are you going to do?   Use the new maximum thrust just because you can?  That seems wrong, running at higher ratings surely increases the risk.  Swap if for a booster with crappier engines?  That seems wrong too.

I believe the Shuttle had engine settings which were developed, and qualified, but never intended to be used.  They were reserved for abort scenarios.
Every time SpaceX introduced more powerfull engines on their rockets they immediately made use of the increased power. There is no valid reason not to do so.

Online Comga

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Is this a block 4 F9? If so what are the improvements vs B3?

This is the first Block 4 first stage. Block 4 second stages have been flying for some time now.

We’ve heard about thrust upgrades and things like bolted octawebs, but nothing super concrete.

It’s basically just a bunch of small hardware upgrades they threw together on their way up to Block 5. We probably wouldn’t even notice the upgrade, especially considering we didn’t notice the Block 2 and 3 upgrades.
you will notice some of the block 4 differences if you have a good eye and watch the flight footage and not all are small differences but most are. I'll leave you with that until launch day.

So?
Did I miss a post from you after launch day that explains what changes should have been visible?
Someone suggested the angle of attach for the retuning first stage.
It was also said that the legs were reused, but while that may be the first time that doesn't fit your description of "new".
What else?
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Online abaddon

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Every time SpaceX introduced more powerfull engines on their rockets they immediately made use of the increased power. There is no valid reason not to do so.
There's always a first time.  And it's quite likely NASA wouldn't want to be the first mission to use higher thrust levels.  It seems to me the most plausible explanation for both a) this being the first "block 4" booster with uprated engines and b) seeing a profile consistent with previous boosters.

Online abaddon

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(from the update thread)
Looks like it is coming down real slow.
Why not?  Plenty of margin to play with, clearly.

Offline garidan

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NASA boosters are new, but boosters are reused thereafter. So it makes sense to use new full thrust engines even if not useful for its first mission.

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Offline octavo

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  May have been the 1.7Mlb-f version just flown below the new maximum thrust level though.  Not necessarily inconsistent to have info saying that CRS-12 flew with up-rated engines and data showing that the launch didn't, assuming the higher maximum, use full thrust. 
You don't fly higher-thrust engines for the first time if you do not intend to utilize that higher thrust.
This is not obvious to me.  At some point you start qualifying your engines to a new, higher, maximum thrust.  You incorporate the new engines into new boosters as they are built.   Now suppose the first mission for the new booster does not require the new maximum thrust.   What are you going to do?   Use the new maximum thrust just because you can?  That seems wrong, running at higher ratings surely increases the risk.  Swap if for a booster with crappier engines?  That seems wrong too.

I believe the Shuttle had engine settings which were developed, and qualified, but never intended to be used.  They were reserved for abort scenarios.
Every time SpaceX introduced more powerfull engines on their rockets they immediately made use of the increased power. There is no valid reason not to do so.
Higher thrust = increased engine wear = increased refurbishment time + cost.

If the performance isn't needed on this mission, why stress the engines more than necessary? Wouldn't you rather reduce the time and cost of refurbishment and possibly extend the booster lifetime?

Online AncientU

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Every time SpaceX introduced more powerfull engines on their rockets they immediately made use of the increased power. There is no valid reason not to do so.
There's always a first time.  And it's quite likely NASA wouldn't want to be the first mission to use higher thrust levels.  It seems to me the most plausible explanation for both a) this being the first "block 4" booster with uprated engines and b) seeing a profile consistent with previous boosters.

Not the track record so far... CRS flights have been incredibly supportive of the changes and development efforts.  The folks over at Commercial crew should watch and learn.

Landing a Dragon 2 with inherent stability of a capsule and a low terminal velocity is much simpler than these booster landings.
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Online AncientU

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  May have been the 1.7Mlb-f version just flown below the new maximum thrust level though.  Not necessarily inconsistent to have info saying that CRS-12 flew with up-rated engines and data showing that the launch didn't, assuming the higher maximum, use full thrust. 
You don't fly higher-thrust engines for the first time if you do not intend to utilize that higher thrust.
This is not obvious to me.  At some point you start qualifying your engines to a new, higher, maximum thrust.  You incorporate the new engines into new boosters as they are built.   Now suppose the first mission for the new booster does not require the new maximum thrust.   What are you going to do?   Use the new maximum thrust just because you can?  That seems wrong, running at higher ratings surely increases the risk.  Swap if for a booster with crappier engines?  That seems wrong too.

I believe the Shuttle had engine settings which were developed, and qualified, but never intended to be used.  They were reserved for abort scenarios.
Every time SpaceX introduced more powerfull engines on their rockets they immediately made use of the increased power. There is no valid reason not to do so.
Higher thrust = increased engine wear = increased refurbishment time + cost.

If the performance isn't needed on this mission, why stress the engines more than necessary? Wouldn't you rather reduce the time and cost of refurbishment and possibly extend the booster lifetime?

Are you sure the engines are not higher capability with same margin as before? There is much counter-evidence that your naive equality above is true -- the 24 hour turn-around and ten reuses without refurbishment on Block 5s completely contradicts your intuition.
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