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#460
by
mme
on 27 Mar, 2017 18:14
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I'm a fan of SpaceX, I think they will succeed and I believe they have done all their homework for this flight.
But claiming "no biggie, it's insured" for the customer does not recognize that satellites take years to build and companies like SES, Iridium, Orbcomm, and dare I mention Spacecom make their livelihood by those satellites being operational in orbit.
My house is insured but if it burns down it's still going to suck. If I ever meet the CTO of SES, I'm buying the man a drink for supporting SpaceX and reusable rockets. Even though I am sure he got a sweet deal for this flight.
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#461
by
rsdavis9
on 27 Mar, 2017 18:17
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Has anybody considered the PR that companies like SES get for being the first to launch on a new spacex configuration. I know that personally I know a lot more about SES now then before their flights. I think Iridium got a boost from the PR too.
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#462
by
rockets4life97
on 27 Mar, 2017 18:19
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Any reason for the longer burn? Special request by SES?
Does it result in better data being collected (vs a 3 second burn)? If yes, why not make 5 second burns standard?
I think I remember someone saying the 5 sec burn allows them to get a better checkout of the turbopumps.
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#463
by
Lar
on 27 Mar, 2017 18:33
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Any reason for the longer burn? Special request by SES?
Does it result in better data being collected (vs a 3 second burn)? If yes, why not make 5 second burns standard?
I think I remember someone saying the 5 sec burn allows them to get a better checkout of the turbopumps.
Which does kind of revalidate the question... why not do this for all? I honestly have no idea. Might be off topic for a mission specific thread. Maybe we need a "how long to static fire" thread!
Or a poll. (KIDDING)
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#464
by
ChrisGebhardt
on 27 Mar, 2017 18:46
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Any reason for the longer burn? Special request by SES?
Does it result in better data being collected (vs a 3 second burn)? If yes, why not make 5 second burns standard?
I think I remember someone saying the 5 sec burn allows them to get a better checkout of the turbopumps.
Which does kind of revalidate the question... why not do this for all? I honestly have no idea. Might be off topic for a mission specific thread. Maybe we need a "how long to static fire" thread! Or a poll. (KIDDING)
As they've only done (to my memory) the prolonged static fire for the two SES missions to date, I'd place good money on it being a customer request.
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#465
by
rsdavis9
on 27 Mar, 2017 18:48
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Any reason for the longer burn? Special request by SES?
Does it result in better data being collected (vs a 3 second burn)? If yes, why not make 5 second burns standard?
I think I remember someone saying the 5 sec burn allows them to get a better checkout of the turbopumps.
Which does kind of revalidate the question... why not do this for all? I honestly have no idea. Might be off topic for a mission specific thread. Maybe we need a "how long to static fire" thread! Or a poll. (KIDDING)
As they've only done (to my memory) the prolonged static fire for the two SES missions to date, I'd place good money on it being a customer request.
So whats the TEL umbilical damage like for A static fire? Does the longer burn do more damage?
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#466
by
kevinof
on 27 Mar, 2017 18:53
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I assume none as it never contacts the exhaust. It's only (?) as the stage climbs off the pad that the heat and exhaust impacts the tel and causes damage.
Any reason for the longer burn? Special request by SES?
Does it result in better data being collected (vs a 3 second burn)? If yes, why not make 5 second burns standard?
I think I remember someone saying the 5 sec burn allows them to get a better checkout of the turbopumps.
Which does kind of revalidate the question... why not do this for all? I honestly have no idea. Might be off topic for a mission specific thread. Maybe we need a "how long to static fire" thread! Or a poll. (KIDDING)
As they've only done (to my memory) the prolonged static fire for the two SES missions to date, I'd place good money on it being a customer request.
So whats the TEL umbilical damage like for A static fire? Does the longer burn do more damage?
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#467
by
ChrisGebhardt
on 27 Mar, 2017 18:55
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I assume none as it never contacts the exhaust. It's only (?) as the stage climbs off the pad that the heat and exhaust impacts the tel and causes damage.
Any reason for the longer burn? Special request by SES?
Does it result in better data being collected (vs a 3 second burn)? If yes, why not make 5 second burns standard?
I think I remember someone saying the 5 sec burn allows them to get a better checkout of the turbopumps.
Which does kind of revalidate the question... why not do this for all? I honestly have no idea. Might be off topic for a mission specific thread. Maybe we need a "how long to static fire" thread! Or a poll. (KIDDING)
As they've only done (to my memory) the prolonged static fire for the two SES missions to date, I'd place good money on it being a customer request.
So whats the TEL umbilical damage like for A static fire? Does the longer burn do more damage?
Correct. No TEL umbilical damage from a nominal static fire.
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#468
by
ugordan
on 27 Mar, 2017 18:56
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As they've only done (to my memory) the prolonged static fire for the two SES missions to date, I'd place good money on it being a customer request.
+ Jason-3
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#469
by
THeel01
on 27 Mar, 2017 19:28
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Can someone double check my math?
By my count, the current record for pad turnaround for launches on either LC39A/B is 17 days (STS- 51-D to STS-51-B, launched from LC39A).
Not to start Go-fever or anything, but if SpaceX launches on Mar 30, thats 14 day turnaround.
Sound correct?
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#470
by
Mike_1179
on 27 Mar, 2017 19:43
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As they've only done (to my memory) the prolonged static fire for the two SES missions to date, I'd place good money on it being a customer request.
If this static fire is meant to mimic the ignition and hold down of a real launch, does that mean they intend to hold the vehicle down for 5 seconds after ignition on the 30th as well?
The downside is 2 seconds less prop at the end of a first stage burn but my guess is it lets them characterize the engine performance prior to hold-down release better once you get further away from start-up transients and they operate at steady state. Might be that's why this is a "customer request" because the customer is getting 2 seconds less margin (about 500 kg of fuel, right?)
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#471
by
ChrisGebhardt
on 27 Mar, 2017 20:01
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As they've only done (to my memory) the prolonged static fire for the two SES missions to date, I'd place good money on it being a customer request.
If this static fire is meant to mimic the ignition and hold down of a real launch, does that mean they intend to hold the vehicle down for 5 seconds after ignition on the 30th as well?
The downside is 2 seconds less prop at the end of a first stage burn but my guess is it lets them characterize the engine performance prior to hold-down release better once you get further away from start-up transients and they operate at steady state. Might be that's why this is a "customer request" because the customer is getting 2 seconds less margin (about 500 kg of fuel, right?)
No. Sequence on launch day will result in nominal release time at T0.
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#472
by
Orbiter
on 27 Mar, 2017 20:11
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Can someone double check my math?
By my count, the current record for pad turnaround for launches on either LC39A/B is 17 days (STS- 51-D to STS-51-B, launched from LC39A).
Not to start Go-fever or anything, but if SpaceX launches on Mar 30, thats 14 day turnaround.
Sound correct?
Yes, assuming the schedule holds, the turnaround between Echostar-23 and SES-10 will be the fastest ever from LC-39A. However, the Shuttle was a far different beast.
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#473
by
ATPTourFan
on 27 Mar, 2017 20:54
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No. Sequence on launch day will result in nominal release time at T0.
I would agree, clamps release at T-0, but would ignition sequence start earlier?
It's a good question because I thought the "only" thing different between static hold-down fire pre-launch was that they didn't let go (I know that's oversimplified). Or is the static fire a modified sequence that only mimics the pad operations and fuel loading profile for the launch through to engine ignition, and not necessarily a mirror of the last 5 seconds prior to T-0?
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#474
by
ChrisGebhardt
on 27 Mar, 2017 21:15
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No. Sequence on launch day will result in nominal release time at T0.
I would agree, clamps release at T-0, but would ignition sequence start earlier?
It's a good question because I thought the "only" thing different between static hold-down fire pre-launch was that they didn't let go (I know that's oversimplified). Or is the static fire a modified sequence that only mimics the pad operations and fuel loading profile for the launch through to engine ignition, and not necessarily a mirror of the last 5 seconds prior to T-0?
No. The countdown sequence will be nominal. No extra time or early ignition, etc.. The static fire duration does not translate to changes to launch countdown.
Static fire is a mirror of everything down to T0. If it helps, a good way to think of today is that they proceeded past T0 to T+2secs, but didn't release the clamps. That's a better way to view this than a change to countdown/launch day/release timing.
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#475
by
mn
on 27 Mar, 2017 21:30
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How many seconds between ignition and T0?
Is this time consistent or has anyone noticed that number moving around on various launches?
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#476
by
ugordan
on 27 Mar, 2017 21:34
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Chamber ignition occurs at around T-2 sec with TEA/TEB starting flowing about a second before that. Has been that way for IIRC as long as M1D existed.
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#477
by
ChrisC
on 27 Mar, 2017 22:45
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#478
by
intrepidpursuit
on 27 Mar, 2017 23:19
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#479
by
DatUser14
on 27 Mar, 2017 23:32
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How many seconds between ignition and T0?
Is this time consistent or has anyone noticed that number moving around on various launches?
Looked at the last couple press kits, it's been T-3 Merlin-1D ignition T-0 liftoff.
Or a poll. (KIDDING)