lnglive1011yyz
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Shuttle Flight Readiness Firings?

Mon Aug 18, 2008 2:22 am

Hey all,

I've been just looking at videos online of the FRF's performed back in the 80's and when Endeavour came on board, and I'm curious..

Does NASA still perform FRF's?

If no.. is there a reason why?

Thanks !

1011
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Thorny
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RE: Shuttle Flight Readiness Firings?

Mon Aug 18, 2008 3:34 am



Quoting Lnglive1011yyz (Thread starter):
Does NASA still perform FRF's?
If no.. is there a reason why?

No, they were used to verify the entirely of the Orbiter/External Tank main propulsion system before each Orbiter's first flight. Challenger's FRF indicated a leak, leading to a second FRF. Discovery performed an FRF prior to the STS-26 return to flight in 1988 primarily to exercise the launch team following the prolonged standdown. This wasn't repeated for STS-114 in 2005 because by then there had been over 100 Shuttle launches and it wasn't considered necessary anymore. Also, the downtime wasn't expected to be as long as it turned out to be, and potential ET foam shedding led NASA to limit the number of fill/drain cycles on an External Tank to only those absolutely necessary.
 
lnglive1011yyz
Posts: 1502
Joined: Thu Oct 23, 2003 12:23 pm

RE: Shuttle Flight Readiness Firings?

Mon Aug 18, 2008 9:33 pm



Quoting Thorny (Reply 1):
No, they were used to verify the entirely of the Orbiter/External Tank main propulsion system before each Orbiter's first flight. Challenger's FRF indicated a leak, leading to a second FRF

Thanks for the response.

The tie-down bolts on those boosters must be insanely strong.

If you look at most of the videos, it's quite cool to see the Shuttle Stack doing the 'wobble' back and forth prior to the videos ending!

1011yyz
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Blackprojects
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RE: Shuttle Flight Readiness Firings?

Mon Aug 18, 2008 10:31 pm

Here is one of the Launch Tie Down Explosive Bolts concerned.

http://nasatech.net/Bolt%20Catchers/images/BoosterSepHardware06a.jpg

Booster Seperation Hardware!

http://nasatech.net/Bolt%20Catchers/
 
Thorny
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RE: Shuttle Flight Readiness Firings?

Mon Aug 18, 2008 10:50 pm



Quoting Lnglive1011yyz (Reply 2):
If you look at most of the videos, it's quite cool to see the Shuttle Stack doing the 'wobble' back and forth prior to the videos ending!

They call it the "twang". The STS-1 countdown was a little different from later ones based on experience with the twang. For STS-1, the Mains fired at T-3.8 seconds, they let the ET twang to the north and then back to vertical for SRB ignition. Later flights had the Mains fire at T-6.6 and they let the ET go through one complete cycle, twang north, through vertical to twang south, and then back to vertical for SRB ignition.
 
DfwRevolution
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RE: Shuttle Flight Readiness Firings?

Tue Aug 19, 2008 12:48 am



Quoting Lnglive1011yyz (Reply 2):
The tie-down bolts on those boosters must be insanely strong.

The Shuttle stack has 4 hold-down bolts on each SRB that measure 28 inches long and 3.5 inches in diameter. IMO, that's nothing special in the engineering world.

Also keep in mind that the three SSME produce about 1.2 million lbs of sea level thrust while the stack weights over 4 million lbs at liftoff. The SSME aren't capable of accelerating the Shuttle vertically during a FRF or warm-up/verification.
 
lnglive1011yyz
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RE: Shuttle Flight Readiness Firings?

Tue Aug 19, 2008 1:52 am

Quoting DfwRevolution (Reply 5):
The Shuttle stack has 4 hold-down bolts on each SRB that measure 28 inches long and 3.5 inches in diameter. IMO, that's nothing special in the engineering world.

Also keep in mind that the three SSME produce about 1.2 million lbs of sea level thrust while the stack weights over 4 million lbs at liftoff. The SSME aren't capable of accelerating the Shuttle vertically during a FRF or warm-up/verification.

Good point. But, to the uneducated, it would appear to be amazing! (Still is, nonetheless)

Quoting Thorny (Reply 4):

They call it the "twang". The STS-1 countdown was a little different from later ones based on experience with the twang. For STS-1, the Mains fired at T-3.8 seconds, they let the ET twang to the north and then back to vertical for SRB ignition. Later flights had the Mains fire at T-6.6 and they let the ET go through one complete cycle, twang north, through vertical to twang south, and then back to vertical for SRB ignition.

Wow! Thanks for the info. I'll go back and review the vids!

Is there any functional reason why? I noticed that late in the launch, there's a call from Capcom to Columbia indicating that they were a bit high on their trajectory or something.. Is that why?


1011yyz

[Edited 2008-08-18 18:54:14]

[Edited 2008-08-18 18:54:50]
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DfwRevolution
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RE: Shuttle Flight Readiness Firings?

Tue Aug 19, 2008 4:46 am



Quoting Lnglive1011yyz (Reply 6):
I noticed that late in the launch, there's a call from Capcom to Columbia indicating that they were a bit high on their trajectory or something.. Is that why?

No, that call is in reference to the fact that the Columbia was performing better than expected. In one of the post mission conferences, Crippen alluded to the fact that because the Shuttle climbed faster than expected, it would allow more payload in the future.

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