Author Topic: Static fire costs?  (Read 7679 times)

Offline Lar

  • Fan boy at large
  • Global Moderator
  • Senior Member
  • *****
  • Posts: 13463
  • Saw Gemini live on TV
  • A large LEGO storage facility ... in Michigan
  • Liked: 11864
  • Likes Given: 11086
Re: Static fire costs?
« Reply #20 on: 04/07/2019 11:23 am »

SpaceX must have a good body of knowledge know how much "coking" is acceptable before a cleaning is required.  If they are planning to do a 24-hour turn around on a booster, that doesn't give much time to de-coke the engine.   
Indeed. Coke (and soot) deposition may be non linear, though (as in, a prior deposit may cause more new coke to form than if the engine is brand new) I expect that as we see different "class leaders" get to different numbers of reflights on them we will see (evidence of[1]) teardowns at 5, 7, etc engine reflights to see what the buildup looks like and refine the "10 flights before overhaul" number based on actual coking experience.

(by the way I think this is both normal for SpaceX and awesome, all at the same time... unlike Shuttle which saw a very very slow feedback loop, if any, for things found, SpaceX iterates rapidly)

1 - evidence in that a booster is taken out of the rotation for enough time that a teardown could have been done ...
« Last Edit: 04/07/2019 11:24 am by Lar »
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline MechE31

  • Full Member
  • *
  • Posts: 156
  • MELBOURNE, FL
  • Liked: 284
  • Likes Given: 1
Re: Static fire costs?
« Reply #21 on: 04/07/2019 04:24 pm »
On the original question, the only real engine work done between static fire and launch is cleaning the fuel film cooling holes (aluminum oxide from the tea/teb) and fuel drain and flush.

Offline envy887

  • Senior Member
  • *****
  • Posts: 8144
  • Liked: 6801
  • Likes Given: 2965
Re: Static fire costs?
« Reply #22 on: 04/07/2019 04:46 pm »
On the original question, the only real engine work done between static fire and launch is cleaning the fuel film cooling holes (aluminum oxide from the tea/teb) and fuel drain and flush.
This cleaning is done without pulling the engines off the vehicle, right?

Offline MechE31

  • Full Member
  • *
  • Posts: 156
  • MELBOURNE, FL
  • Liked: 284
  • Likes Given: 1
Re: Static fire costs?
« Reply #23 on: 04/07/2019 04:58 pm »
On the original question, the only real engine work done between static fire and launch is cleaning the fuel film cooling holes (aluminum oxide from the tea/teb) and fuel drain and flush.
This cleaning is done without pulling the engines off the vehicle, right?

Correct

Offline starsilk

  • Full Member
  • ****
  • Posts: 686
  • Denver
  • Liked: 268
  • Likes Given: 115
Re: Static fire costs?
« Reply #24 on: 04/08/2019 02:53 pm »
Can we agree that the "man" hours to turn around 9 Merlin Rocket engines to be ready to fire again is considerably less than other equivalent engines because the Merlin rocket engine was designed to be used repeatedly?   
I think so, yeah... But our opinion counts for a lot less than the view of the CFO of SpaceX....

Which goes back to my point, the Merlin was designed for repeated fires.  So the static fire is the byproduct of a reusable design.  ULA doesn't do static fires because the RD-180 wasn't designed for repeated fires because it isn't a re-usable engine. 

AFAIK RD-180 IS a reusable engine. It is based on RD-170 which used in the boosters of the soviet space shuttle program, and they had plans for recovering and reusing the boosters.

RD-180 is reusable but it requires some 'refurbishment' between firings, there are single use parts that have to be replaced (ISTR mostly minor stuff, welch plugs etc)

Offline Lar

  • Fan boy at large
  • Global Moderator
  • Senior Member
  • *****
  • Posts: 13463
  • Saw Gemini live on TV
  • A large LEGO storage facility ... in Michigan
  • Liked: 11864
  • Likes Given: 11086
Re: Static fire costs?
« Reply #25 on: 04/08/2019 09:39 pm »
That engine has welch plugs? my Google-fu tells me those are also called core plugs or freezeout plugs and are usually found in internal combustion engines...
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline starsilk

  • Full Member
  • ****
  • Posts: 686
  • Denver
  • Liked: 268
  • Likes Given: 115
Re: Static fire costs?
« Reply #26 on: 04/08/2019 10:35 pm »
That engine has welch plugs? my Google-fu tells me those are also called core plugs or freezeout plugs and are usually found in internal combustion engines...

burst disks? been a while since I looked at it.

Offline Lar

  • Fan boy at large
  • Global Moderator
  • Senior Member
  • *****
  • Posts: 13463
  • Saw Gemini live on TV
  • A large LEGO storage facility ... in Michigan
  • Liked: 11864
  • Likes Given: 11086
Re: Static fire costs?
« Reply #27 on: 04/09/2019 02:35 am »
That engine has welch plugs? my Google-fu tells me those are also called core plugs or freezeout plugs and are usually found in internal combustion engines...

burst disks? been a while since I looked at it.
That's another name for them, agreed. I just was wondering why this (or any) rocket engine needs them. This might be a bit of a rathole sorry.
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline oiorionsbelt

  • Full Member
  • ****
  • Posts: 1766
  • Liked: 1190
  • Likes Given: 2685
Re: Static fire costs?
« Reply #28 on: 04/11/2019 03:26 am »

Can we agree that the "man" hours to turn around 9 Merlin Rocket engines to be ready to fire again is considerably less than other equivalent engines because the Merlin rocket engine was designed to be used repeatedly?   


We know that some of them can be fired at least four times with 0 man hours between firings because they were designed to be used repeatedly on each flight.

Offline Tulse

  • Full Member
  • ****
  • Posts: 546
  • Liked: 395
  • Likes Given: 3
Re: Static fire costs?
« Reply #29 on: 04/12/2019 03:03 pm »
Are the main maintenance issues with repeated firings, or with the total firing time?  I would guess that with a methalox engine, where coking is much less of a problem, the main concerns are stresses with startup/shutdown, but are there issues with just the length of time the engine runs?

Tags:
 

Advertisement NovaTech
Advertisement Northrop Grumman
Advertisement
Advertisement Margaritaville Beach Resort South Padre Island
Advertisement Brady Kenniston
Advertisement NextSpaceflight
Advertisement Nathan Barker Photography
1