Author Topic: FRF question  (Read 4577 times)

Offline Ben E

  • Full Member
  • ****
  • Posts: 1000
  • Liked: 10
  • Likes Given: 0
FRF question
« on: 05/01/2006 05:09 PM »
I'm aware that, prior to each orbiter's first flight, a Flight Readiness Firing of the main engines was conducted. Before STS-1, Columbia's engines were run up to 100% (full) power. Challenger's engines were capable of a slightly higher thrust, going up to 104%.

Does anyone know if Challenger's FRF ran the engines up to 104%, or 'just' up to 100%?

Thanks

Offline Jim

  • Night Gator
  • Senior Member
  • *****
  • Posts: 32377
  • Cape Canaveral Spaceport
  • Liked: 11063
  • Likes Given: 329
RE: FRF question
« Reply #1 on: 05/01/2006 05:19 PM »
Quote
Ben E - 1/5/2006  1:09 PMI'm aware that, prior to each orbiter's first flight, a Flight Readiness Firing of the main engines was conducted. Before STS-1, Columbia's engines were run up to 100% (full) power. Challenger's engines were capable of a slightly higher thrust, going up to 104%.Does anyone know if Challenger's FRF ran the engines up to 104%, or 'just' up to 100%?Thanks

All Shuttles are capable of 104% thrust.  They launch a 100% and throttle up to (now days) 104.5% after liftoff.

Offline psloss

  • Veteran armchair spectator
  • Senior Member
  • *****
  • Posts: 17302
  • Liked: 1773
  • Likes Given: 1011
RE: FRF question
« Reply #2 on: 05/01/2006 05:56 PM »
I believe the FRFs went to 100% -- with the possible exception of Columbia's pre STS-1 FRF, which I recall Aviation Week reporting to have some throttling and gimbaling after "T-0".  Though I don't know if I ever saw it noted elsewhere...

One of the things about the FRFs that I thought was interesting was the shutdown sequence -- it probably wasn't any different than the pad shutdowns, but some of the cutoffs on the pad occurred before all the engines got up to full power (or in some cases before some of the engines got a start command).

In the footage I've seen of more "recent" pad shutdowns (FRF or not), the engines are shutdown in the reverse sequence of start -- one, two, three (center, left, right) -- and staggered by a second or so.  (This can be seen in the FRF prior to STS-26 as well as the STS-68 pad abort.)  

In the second Challenger FRF before STS-6, the video shows that engines two and three were shutdown much closer together after engine 1.  I haven't seen footage of the other pre-51-L shutdowns, but perhaps this was the logic back then.

Anyone here know why the difference?

Thanks,

Philip Sloss



Offline mkirk

  • International Man Of Mystery
  • Full Member
  • ****
  • Posts: 1730
  • Florida/Texas
  • Liked: 32
  • Likes Given: 0
RE: FRF question
« Reply #3 on: 05/01/2006 10:37 PM »
Quote
Ben E - 1/5/2006  12:09 PM

I'm aware that, prior to each orbiter's first flight, a Flight Readiness Firing of the main engines was conducted. Before STS-1, Columbia's engines were run up to 100% (full) power. Challenger's engines were capable of a slightly higher thrust, going up to 104%.

Does anyone know if Challenger's FRF ran the engines up to 104%, or 'just' up to 100%?

Thanks

To my knowledge all the FRFs used 100% for the same reason we start and launch at 100%...the accoustic load from the MLP (mobile launch platform) on the orbiter side of the stack is too high and could damage the orbiter.  During launch the throttle command for 104.5% is not issued until about 4 seconds after liftoff when the stack is further away from the MLP.

When I can get to my old FRF documents I will double check.

Mark Kirkman
Mark Kirkman

Offline GLS

  • Member
  • Full Member
  • *
  • Posts: 169
  • Liked: 0
  • Likes Given: 0
RE: FRF question
« Reply #4 on: 05/04/2006 11:07 AM »
I think all FRFs were at 100%, and the FRF on OV-102 had gimbaling after T0. There was also a *wall* below the body flap, between the SSMEs and the SRBs as there were concerns about the heat from the SSMEs igniting the solids...
Now, looking at the videos, this it what I know: The shutdown sequence was 1-2/3 on all FRFs. The FRF on OV-102, both FRFs on OV-099 and the FRF on OV-105 had ME-1 cutoff at T+15sec, and ME-2 and ME-3 at T+16.8sec. The 2 FRFs on OV-103 and the FRF of OV-104 had ME-1 cutoff at T+11sec, and ME-2 and ME-3 at T+13sec.

Not much but this is all I know....
GLS is go for main engine start!

Offline psloss

  • Veteran armchair spectator
  • Senior Member
  • *****
  • Posts: 17302
  • Liked: 1773
  • Likes Given: 1011
RE: FRF question
« Reply #5 on: 05/04/2006 01:11 PM »
Quote
GLS - 4/5/2006  7:07 AM

I think all FRFs were at 100%, and the FRF on OV-102 had gimbaling after T0. There was also a *wall* below the body flap, between the SSMEs and the SRBs as there were concerns about the heat from the SSMEs igniting the solids...
Now, looking at the videos, this it what I know: The shutdown sequence was 1-2/3 on all FRFs. The FRF on OV-102, both FRFs on OV-099 and the FRF on OV-105 had ME-1 cutoff at T+15sec, and ME-2 and ME-3 at T+16.8sec. The 2 FRFs on OV-103 and the FRF of OV-104 had ME-1 cutoff at T+11sec, and ME-2 and ME-3 at T+13sec.
It's minutiae, but I believe the two post-Challenger FRFs had the 1-2-3 shutdown sequence and I know that's the case for Discovery's second FRF...I don't have the tape of the FRF prior to STS-26 with me right now, but the post-firing replays showed this...

Offline shuttlefan

  • Member
  • Full Member
  • ****
  • Posts: 1608
  • Liked: 13
  • Likes Given: 4
RE: FRF question
« Reply #6 on: 05/07/2006 06:16 PM »
Does anybody think there will be another FRF in the last years of Shuttle?

Offline Jim

  • Night Gator
  • Senior Member
  • *****
  • Posts: 32377
  • Cape Canaveral Spaceport
  • Liked: 11063
  • Likes Given: 329
RE: FRF question
« Reply #7 on: 05/07/2006 06:31 PM »
Quote
shuttlefan - 7/5/2006  2:16 PMDoes anybody think there will be another FRF in the last years of Shuttle?
No reason to.  If there is a reason, it's because something went wrong, and I think the program would be shutdown first.

Offline GLS

  • Member
  • Full Member
  • *
  • Posts: 169
  • Liked: 0
  • Likes Given: 0
RE: FRF question
« Reply #8 on: 05/09/2006 10:20 AM »
I've been looking at some photos and the *wall* between the SSMEs and the SRBs was used on all FRFs.... I had read that it was used for OV-102's FRF, but apparently it was always used!
GLS is go for main engine start!

Offline psloss

  • Veteran armchair spectator
  • Senior Member
  • *****
  • Posts: 17302
  • Liked: 1773
  • Likes Given: 1011
RE: FRF question
« Reply #9 on: 05/09/2006 11:31 AM »
Quote
GLS - 9/5/2006  6:20 AM

I've been looking at some photos and the *wall* between the SSMEs and the SRBs was used on all FRFs.... I had read that it was used for OV-102's FRF, but apparently it was always used!
I thought I heard it referred to as a blast shield or something like that; it does make it easier to identify related photos.  I've attached a couple of stills from the 51-J and STS-26 FRFs that show it from the FSS.

Philip Sloss

Offline Ben E

  • Full Member
  • ****
  • Posts: 1000
  • Liked: 10
  • Likes Given: 0
RE: FRF question
« Reply #10 on: 05/09/2006 03:19 PM »
Why was there an FRF before STS-26 and not before STS-114?

Offline Jim

  • Night Gator
  • Senior Member
  • *****
  • Posts: 32377
  • Cape Canaveral Spaceport
  • Liked: 11063
  • Likes Given: 329
RE: FRF question
« Reply #11 on: 05/09/2006 03:29 PM »
Quote
Ben E - 9/5/2006  11:19 AMWhy was there an FRF before STS-26 and not before STS-114?

There was a WDR or Wet TCDT, which tested the launch team..  It was felt that there was nothing to gain by firing the engines

Offline Steve_the_Deev

  • Regular
  • Full Member
  • *
  • Posts: 138
  • Liked: 2
  • Likes Given: 0
RE: FRF question
« Reply #12 on: 05/10/2006 06:03 AM »
During an in-flight abort situation i.e. a one engine fail or two engine fail and it depends on many other factors but there is a 109% SSME thrust profile available.

I am glad to see that everyone here is really up to the FRF reqmnt. I was present and wrote the Post FRF MPS/SSME test and checkout procedure for Discovery and on. The Post Challenger STS-26R (Discovery Return to Flight FRF) done per my OMI V1075 was a huge step up from the standard post FRF MPS testing, I had to totaly rewrite the entire procedure especially since the GOX High Pressure side/FCVs (Flow Control Valves) was redesigned as was the GH2 Repress system. Yep we had to basically test everything! As the years went by and we gained confidence in the Orbiter's we once again went through and changed many of the test reqmnts so we could make schedule!

OV-104 then OV-105's FRF Post Test and Checkout was probably 2/3 rds the testing we did for the first RTF FRF for STS-26R.

FRFs test the first time that the new Orbiter's MPS Integrates with the SSMEs (already certified at NSTL) and the ET. FRF's ran for about 19 seconds if I remember correctly. If we had a major rework of the MPS's Hot Gas or Cryo systems we would have to make a team decision on whether or not an FRF would be run.  It was always meant for first flight of a new vehicle but if Marshall and JSC and KSC felt that there was enough rework of the MPS on any vehicle I believe the File II OMRSD for FRF allows a Contingency action to allow us to run an FRF for a second time on the Orbiter.

Good work here!  FYI

The Super Light weight ETs saved a lot of weight once Lockheed learned how to handle Aluminum-Lithium. (Do not breath in the "dust" of AL-Li during maching, it's a bad combo for the Brain)!  I heard the Russians gave us some tips on how to forge and or weld Al-Li for various Aerospace structures. We had Al-Li stringers on the Atlas vehicle's Payload Adapter when I worked on that program in Harlingen,TX. Pretty cool to be on the manufacturing side of a Launch vehicle.

Steve_the_Deev ;)

Offline shuttlefan

  • Member
  • Full Member
  • ****
  • Posts: 1608
  • Liked: 13
  • Likes Given: 4
RE: FRF question
« Reply #13 on: 05/14/2006 03:22 PM »
I think the important thing to remember about an FRF is that it is not just about testing the SSMEs. An FRF serves as a great test to accomplish alot of knowledge about all the systems on the shuttle vehicle. It is the only test in which all the systems on the vehicle are activated during a real countdown, without launching.
 I think the STS-26 FRF was mostly about getting the launch team back into a posture of putting a vehicle through a full countdown and then having to safe it again after an SSME abort. I know they conduct alot of launch and abort simulations between launches, but it must add alot more, psycologically, to a simulation knowing there is a vehicle out on the pad fully fueled and counting down. Someone correct me if I am wrong about any of this...
Also, I think the reason they didn't conduct an FRF before 114 is that all three of those engines had been thoroughly tested at Stennis before being installed in the ship.
 I hope I score at least a 50% on this essay!! :)  :)  :)

Tags: