Author Topic: Shuttle Questions Q & A (Part 4) (Read 742943 times)

Chris Bergin · « **Reply #100 on:** 11/18/2007 11:02 am »

More people will have an answer in this thread

psloss · « **Reply #101 on:** 11/18/2007 01:17 pm »

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pippin - 18/11/2007 6:51 AM

Shuttle Q&A, there's also an answer to this :-)

Yup; here's one:
http://forum.nasaspaceflight.com/forums/thread-view.asp?tid=625&start=526#M26228

Zoomer30 · « **Reply #102 on:** 11/19/2007 06:19 am »

Thanks for the pointer on the GOX arm on STS 1, I was watching that video going "Hey, wth, thats not they way that works!" I must have missed it during the LIVE broadcast, CBS may not have shown it.

Another question about STS 1 (and I guess every STS flight). I watched on Google Video a STS 1 video where Young and Crippen did their talk about the flight and showed video of the launch. Young pointed out how close the stack comes to the hydrogen feed/vent line service arm. My ? is this....how close DOES it come. From the POV of the FSS, seems like only a few feet. Young also made mention of this during the video for STS 9 (his last flight)

Zoomer30 · « **Reply #103 on:** 11/19/2007 06:27 am »

Oh one more very obscure fact about the GOX arm....when the Enterprise was on Pad 39A they did not even HAVE a GOX arm. At the time it was not in the plans. After a few tests with a filled ET they saw the ice issue. Enter the GOX arm.

AnimatorRob · « **Reply #104 on:** 11/20/2007 04:43 pm »

When being transported on the SCA, how much lift does an orbiter generate. Or, put another way, how much weight does the SCA actually have the lift?

mkirk · « **Reply #105 on:** 11/21/2007 01:44 am »

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AnimatorRob - 20/11/2007 11:43 AM

When being transported on the SCA, how much lift does an orbiter generate. Or, put another way, how much weight does the SCA actually have the lift?

The amount of lift produced is a function of airspeed (among other variables, I will neglect things such as angle of attack and density altitude for now). I don’t know how you would quantify the amount of lift produced by the orbiter and it really doesn’t matter given the amount of drag produced.

You need to think of the orbiter as a massive drag device when it is placed on top of the 74. That is exactly how the SCA crew thinks of it when they do their mission planning and fuel burn computations. The crew can refer to the performance charts (developed by flight and operational testing) that give an estimated fuel burn rate (lbs per nautical mile, hr, etc…) with the orbiter on top. These charts are based on the planned cruise speed and altitude and obviously reflect a huge reduction in performance compared to a a clean 747 (i.e. no orbiter) with the same cargo weight.

The orbiter and its big wings are not any help what-so-ever. Yes the wings produce some lift, and they will produce a greater amount of lift as the airspeed of the SCA is increased, and this will help offset the orbiter weight, however, as the wings produce lift they also produce drag. The orbiter’s fuselage also adds drag and also disrupts the otherwise smooth airflow that moves across the 74’s tail. That is why the horizontal stab has the additional winglets, they compensate for the reduced stability and directional control.

So yes the orbiter does contribute some lift to offset the weight but it doesn’t contribute any thrust to make up for the massive drag increase.

To answer the last part of your question, technically the 74 has to be able to lift all of the orbiter's weight...at least until the takeoff roll begins.

Mark Kirkman

SiameseCat · « **Reply #106 on:** 11/21/2007 03:02 am »

How does the launch guidance know when to throttle down the SSMEs (while the SRBs are attached)? Is it based on time, or Mach number, or what?

Jim · « **Reply #107 on:** 11/21/2007 04:05 am »

"First-stage guidance is active from SRB ignition
through SRB separation command. In this
stage, guidance uses a preflight planned
("canned") table of roll, pitch, and yaw attitudes
referenced to relative velocity. In addition to
sending commands to flight control to obtain
proper attitudes, the guidance software also
sends commands to the MPS throttle per a
preflight defined throttle schedule. Steering of
the vehicle during first stage is accomplished by
gimballing the SSME bells and SRB nozzles.
First-stage guidance also attempts to relieve
vehicle aerodynamic loads based on sensed
accelerations."

mkirk · « **Reply #108 on:** 11/21/2007 02:52 pm »

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SiameseCat - 20/11/2007 10:02 PM

How does the launch guidance know when to throttle down the SSMEs (while the SRBs are attached)? Is it based on time, or Mach number, or what?

Adding to Jim's post, and to answer your question, the throttle commands are based on an earth relative velocity (Vrel) in feet per second. These throttle points can be adjusted during the pre-flight, flight design process.

For example the first throttle up command occurs at a velocity of 60 feet per second (about 3-4 seconds after launch) when the engines are commanded up from 100% to 104.5%. This 60 foot per second value, referred to as an I-load (or initialization load, which is simply a software parameter that can be adjusted) can be adjusted from flight to flight, however, right now it is always set at 60 fps.

Mark Kirkman

thomasafb · « **Reply #109 on:** 11/22/2007 09:22 am »

Hi all,
i seem to remember a handbook that dealt with landing operations at the ELS, including a list of phrases to tell the operators of these sites that an orbiter is inbound.... now i am very sure that i have this file somewhere, but it would be great if someone could help me out with the title so i can find it again....

Many thanks in advance..
Thomas

Endeavour118 · « **Reply #110 on:** 11/22/2007 07:09 pm »

how come all the dockings to the iss i have seen the shuttle dock nose down tale up and with sts-113 the shuttle docks nose up tale down why is that? is that different with the commanders or something else example right here:
http://spaceflight.nasa.gov/gallery/images/shuttle/sts-113/html/sts113-306-011.html

psloss · « **Reply #111 on:** 11/22/2007 08:53 pm »

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Endeavour118 - 22/11/2007 3:09 PM

how come all the dockings to the iss i have seen the shuttle dock nose down tale up and with sts-113 the shuttle docks nose up tale down why is that? is that different with the commanders or something else example right here:
http://spaceflight.nasa.gov/gallery/images/shuttle/sts-113/html/sts113-306-011.html

STS-113 was the same as the other PMA-2/Destiny dockings...compare with STS-120...

Endeavour118 · « **Reply #112 on:** 11/22/2007 10:40 pm »

what nose up tail down?

Jim · « **Reply #113 on:** 11/22/2007 10:58 pm »

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Endeavour118 - 22/11/2007 6:40 PM

what nose up tail down?

They are both pointing the same way

Ronsmytheiii · « **Reply #114 on:** 11/23/2007 12:24 am »

Quote

Endeavour118 - 22/11/2007 3:09 PM

how come all the dockings to the iss i have seen the shuttle dock nose down tale up and with sts-113 the shuttle docks nose up tale down why is that? is that different with the commanders or something else example right here:

They are the same direction, but you might see it as the other way due to the fact that the camera on the truss is "upside down" in relation to what is designated as up.

Zoomer30 · « **Reply #115 on:** 11/23/2007 01:54 am »

Ok I have a "did they ever consider doing this test "question. I know that they at one point were really thinking about using one of the test flights of the Columbia as a RTLS abort test flight. Bascially fly to SRB sep, then simulate some "issue" and swtich to RTLS abort mode and do it. That was quickly dropped since that abort mode is very risky and was not worth the risk for a somewhat low chance of being needed option (ATO, TAA and AOA are much more likely).

Anyway, did they ever consider using Enterprise to do a ALT type test at the KSC runway? I guess they was not much NEED to do one since no landings where planned their till 83 or so (Solar Max mission was the first I think, even though it had been planned for the flight before).

Did they ever think to do that just to get a feel for a landing at the ultra long but ultral narrow KSC strip??

Oberon_Command · « **Reply #116 on:** 11/23/2007 02:14 am »

If Enterprise had entered service as a "flightworthy" orbiter (flying into space), would her paint scheme and TPS systems be configured to be closest to Columbia, Challenger, or the "production orbiters"?

Jim · « **Reply #117 on:** 11/23/2007 02:26 am »

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Oberon_Command - 22/11/2007 10:14 PM

If Enterprise had entered service as a "flightworthy" orbiter (flying into space), would her paint scheme and TPS systems be configured to be closest to Columbia, Challenger, or the "production orbiters"?

Challenger's, since it was OV-099 that replaced it

Jim · « **Reply #118 on:** 11/23/2007 02:28 am »

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Zoomer30 - 22/11/2007 9:54 PM

Did they ever think to do that just to get a feel for a landing at the ultra long but ultral narrow KSC strip??

Sit back and think what would it buy. They could simulate this at EAFB. There are STA's also to fly at the SLF. But the SLF is not ultra narrow, it is 300 feet wide. Shuttle did land on the concrete runways at EAFB.

Zoomer30 · « **Reply #119 on:** 11/23/2007 02:29 am »

Seeing Enterprise as a space worthy shuttle would have been great. But thats just my Star Trek bias coming through.