Author Topic: SpaceX COTS Demo 1 Updates  (Read 618042 times)

Offline Jim

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Re: COTS Demo 1
« Reply #100 on: 08/31/2010 02:10 am »

Remember that the first Falcon 9 launched an hour after a pad abort on engine start.  Just a week earlier, Delta IV had a 48-hour scrub turnaround after a late pad abort because they had to reload some pyro valves.  This contrast speaks to the robustness of the SpaceX architecture.

48hr scrub is not a lack of robustness.

Again, these feature would not be used in any competition.

Offline Jim

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Re: COTS Demo 1
« Reply #101 on: 08/31/2010 02:12 am »
It's also another chance for SpaceX to remind decision makers that competing solutions can't do a static fire test on the pad as easily as they can.  Their full-thrust hold-down and quick recycle capabilities are selling points. 

Remember that the first Falcon 9 launched an hour after a pad abort on engine start.  Just a week earlier, Delta IV had a 48-hour scrub turnaround after a late pad abort because they had to reload some pyro valves.  This contrast speaks to the robustness of the SpaceX architecture.

Really does not matter with the small window for station flights.

Actually think it does.  It's very early days for SpaceX so improvement in turnaround times is to be expected dependant on the issue.  Of course it's preferable not to have an abort in the first place and the 1st flight abort was due to narrow limits which have since been widened therefore unlikely to occur again.
No, the scrub recycle does not matter.   It is unusable for NASA flights.

Offline Antares

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Re: COTS Demo 1
« Reply #102 on: 08/31/2010 03:14 am »
I can't think of any launch vehicle that would be so cavalier as to make a launch attempt without having done a tanking test first.  What a silly idea.

Certainly not a "human rated" one.

Aa-aa-aa-hhemmmmmm.
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Offline ugordan

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Re: COTS Demo 1
« Reply #103 on: 08/31/2010 08:00 am »
I can't think of any launch vehicle that would be so cavalier as to make a launch attempt without having done a tanking test first.  What a silly idea.

Certainly not a "human rated" one.

Aa-aa-aa-hhemmmmmm.

Good one. Gotta love them double standards, eh?

Offline zaitcev

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Re: COTS Demo 1
« Reply #104 on: 09/01/2010 05:39 am »
Remember that the first Falcon 9 launched an hour after a pad abort on engine start.  Just a week earlier, Delta IV had a 48-hour scrub turnaround after a late pad abort because they had to reload some pyro valves.  This contrast speaks to the robustness of the SpaceX architecture.

Really does not matter with the small window for station flights.

Station windows occur every 12 hours, so a 48 hour delay is unpleasantly long. Also, ISS is not going to be the only station ever, hopefuly. Future stations may be located in more convenient orbits, especially if Soyuz is not used for transport.

-- Pete

Offline Lars_J

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Re: COTS Demo 1
« Reply #105 on: 09/01/2010 05:47 am »
Station windows occur every 12 hours, so a 48 hour delay is unpleasantly long. Also, ISS is not going to be the only station ever, hopefuly. Future stations may be located in more convenient orbits, especially if Soyuz is not used for transport.

Since KSC cannot launch into an equatorial orbit, you'll have short launch windows for any space station that is reachable from KSC - no matter the orbit it is in. (Due to phasing)

While there might be a small difference, it should not matter that much, right?


« Last Edit: 09/01/2010 05:49 am by Lars_J »

Offline Jim

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Re: COTS Demo 1
« Reply #106 on: 09/01/2010 11:33 am »
Station windows occur every 12 hours, so a 48 hour delay is unpleasantly long. Also, ISS is not going to be the only station ever, hopefuly. Future stations may be located in more convenient orbits, especially if Soyuz is not used for transport.

Since KSC cannot launch into an equatorial orbit, you'll have short launch windows for any space station that is reachable from KSC - no matter the orbit it is in. (Due to phasing)

While there might be a small difference, it should not matter that much, right?


Not true, look at HST launch windows.

Offline ChefPat

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Re: COTS Demo 1
« Reply #107 on: 09/01/2010 04:36 pm »
I'll make my prediction for launch on November 19. :)
Playing Politics with Commercial Crew is Un-American!!!

Offline Jorge

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Re: COTS Demo 1
« Reply #108 on: 09/01/2010 04:40 pm »
Remember that the first Falcon 9 launched an hour after a pad abort on engine start.  Just a week earlier, Delta IV had a 48-hour scrub turnaround after a late pad abort because they had to reload some pyro valves.  This contrast speaks to the robustness of the SpaceX architecture.

Really does not matter with the small window for station flights.

Station windows occur every 12 hours

Incorrect. The southerly launch azimuth to ISS from KSC is placarded for range safety reasons. Station windows from KSC along the northerly launch azimuth occur every 24 hours. SpaceX will not get an exception for this.
JRF

Offline Jorge

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Re: COTS Demo 1
« Reply #109 on: 09/01/2010 04:43 pm »
Station windows occur every 12 hours, so a 48 hour delay is unpleasantly long. Also, ISS is not going to be the only station ever, hopefuly. Future stations may be located in more convenient orbits, especially if Soyuz is not used for transport.

Since KSC cannot launch into an equatorial orbit, you'll have short launch windows for any space station that is reachable from KSC - no matter the orbit it is in. (Due to phasing)

While there might be a small difference, it should not matter that much, right?


Not true, look at HST launch windows.

Right, a station in an orbit near 28.5 inclination would allow a near due-east launch azimuth that would greatly expand the planar launch window, so the composite launch window winds up being driven by phasing (and is typically almost an hour long).

But for the existing ISS, the planar window will remain around 10 minutes, which pretty much negates SpaceX's quick scrub-turnaround capability.
JRF

Offline beancounter

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Re: COTS Demo 1
« Reply #110 on: 09/02/2010 03:16 am »
Yes I guess it does pretty much.  Ok for a minor hold to check something but not much else.

Would other payloads have longer windows?  If that was so then a quick turnaround capability could be useful.
Beancounter from DownUnder

Offline Jorge

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Re: COTS Demo 1
« Reply #111 on: 09/02/2010 04:20 am »
Yes I guess it does pretty much.  Ok for a minor hold to check something but not much else.

Would other payloads have longer windows?  If that was so then a quick turnaround capability could be useful.

Depends on the payload and whether you're talking deploy or rendezvous. For a payload deploy mission, the launch window can be much longer. For payload rendezvous missions, it's dependent on inclination, with low-inclination payload orbits (like HST) allowing a longer window.
JRF

Offline beancounter

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Re: COTS Demo 1
« Reply #112 on: 09/03/2010 12:46 am »
Yes I guess it does pretty much.  Ok for a minor hold to check something but not much else.

Would other payloads have longer windows?  If that was so then a quick turnaround capability could be useful.

Depends on the payload and whether you're talking deploy or rendezvous. For a payload deploy mission, the launch window can be much longer. For payload rendezvous missions, it's dependent on inclination, with low-inclination payload orbits (like HST) allowing a longer window.

So effort on design for quick turnaround not a total waste and may be useful. 
The other aspect to this quick turnaround design approach (even if never used) would I think be simpler and more efficient systems generally.  This would be a natural consequence of looking at minimising the time taken to undertake any one activity or process which could in turn reduce launch costs.  Flow-on effect.
Beancounter from DownUnder

Offline corrodedNut

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Re: COTS Demo 1
« Reply #113 on: 09/03/2010 11:47 pm »
Space News: "SpaceX Tweaking Falcon 9 Software for Upcoming Launch".

“The second-stage roll is being fixed by changing the location of the [liquid oxygen] pump drain outlet to avoid chilling the hydraulic lines of the roll control actuator,”

So the roll control actuator didn't overheat, it froze? That's interesting. Also, I could have sworn it was electric, not hydraulic.

PS. OK, after reviewing the user guides again I see that the only electromechanical actuators SpaceX uses are for Falcon1 2nd stage/Kestral gimbaling.
« Last Edit: 09/04/2010 12:20 am by corrodedNut »

Offline docmordrid

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Re: COTS Demo 1
« Reply #114 on: 09/04/2010 12:55 am »
What I found interesting in that Space News article is that flt-1was paid for by an un-named "government agency." Sounds like a bit of DoD "alternative funding" to me.

Last year SpaceX said that the military was interested in DragonLab and its optional manipulator arm for rendezvous missions, so it seems to fit that they'd help get Dragon & F9 off the ground.

Wonder what else isn't being said?
« Last Edit: 09/04/2010 01:13 am by docmordrid »
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Offline mr. mark

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Re: COTS Demo 1
« Reply #115 on: 09/04/2010 01:03 am »
Aside from satelitte repair/inspection maybe we are looking at the  US Airforce being one of the first manned Dragon clients.

Online butters

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Re: COTS Demo 1
« Reply #116 on: 09/04/2010 01:55 am »
“The second-stage roll is being fixed by changing the location of the [liquid oxygen] pump drain outlet to avoid chilling the hydraulic lines of the roll control actuator,”

So the roll control actuator didn't overheat, it froze? That's interesting. Also, I could have sworn it was electric, not hydraulic.

PS. OK, after reviewing the user guides again I see that the only electromechanical actuators SpaceX uses are for Falcon1 2nd stage/Kestral gimbaling.

Yeah, the Merlin engines use pressurized RP-1 tapped off the turbopump outlet as the hydraulic fluid.  My understanding is that this is a unique innovation.  Most launch vehicles use a separate APU and pump system for hydraulics.  Kestrel is pressure-fed and therefore uses a different system for actuation.

So I guess the RP-1 froze in the hydraulic line like a clot where the line passed too close to the LOX drain, disabling the roll nozzle actuator.  RP-1 freezes at about -55F, so that scenario is not hard to imagine.  RP-1 also boils at about 395F, so the overheating scenario with radiant heat from the nozzle is also not too hard to imagine.

Offline Jim

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Re: COTS Demo 1
« Reply #117 on: 09/04/2010 02:03 am »
Aside from satelitte repair/inspection maybe we are looking at the  US Airforce being one of the first manned Dragon clients.

The USAF has no manned requirement.

Offline Jim

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Re: COTS Demo 1
« Reply #118 on: 09/04/2010 02:10 am »

Yeah, the Merlin engines use pressurized RP-1 tapped off the turbopump outlet as the hydraulic fluid.  My understanding is that this is a unique innovation.  Most launch vehicles use a separate APU and pump system for hydraulics.  Kestrel is pressure-fed and therefore uses a different system for actuation.


No, the F-1 did it the same way. 
Also, most don't use a separate APU (the few that do are the Redstone, STS and Soyuz), just separate hydraulic fluid.  The hydraulic pump is powered by either the turbopump shaft or using the gas generator

Offline just-nick

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Re: COTS Demo 1
« Reply #119 on: 09/04/2010 04:04 am »

Yeah, the Merlin engines use pressurized RP-1 tapped off the turbopump outlet as the hydraulic fluid.  My understanding is that this is a unique innovation.  Most launch vehicles use a separate APU and pump system for hydraulics.  Kestrel is pressure-fed and therefore uses a different system for actuation.


No, the F-1 did it the same way. 

Don't some of the big russians (RD-170-and-friends) also use fuel-as-hydraulic fluid?

I think confusion on separate hydraulic pump could come from the small electric circulation pumps to keep fluid temperature under control (older Centaurs before they went electromechanical, for example).

Cheers,

  --Nick

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