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#2700 by Quindar Beep on 25 Sep, 2012 16:45
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OK...I have a question about the Shuttle's cross-range capability, particularly the decision to re-design it from one with not much (i.e., Max Faget's "DC-3") to what we actually ended up with.
I know this was done so that the Shuttle could return to Vandenberg after a single polar orbit. But this confuses me as, as I understand it, Vandenberg was going to need a lot of building to handle the Shuttle. So if you're basically building a Shuttle launch facility anyway, I can see -- bearing in mind that I am not a rocket scientist or orbital mechanic -- two other solutions that would have satisfied the "single orbit" criterion without having to add cross-range distance to the orbiter.
So my question is "Why would either of these two solutions not be selected instead?", suspecting that the answer is going to be "cost" or "Quindar, you silly person, that wouldn't work!"
Solution 1: Launch from someplace 1500 miles to the east of Vandenberg (by my calculation, somewhere on a line running north/south from about Oklahoma City), then land at Vandenberg one orbit later. Obvious downside: you're building and manning two facilities instead of one, so cost. But as much extra cost as building the redesigned orbiters as compared to Faget's design? You're also launching over land, but then so is Vandenberg, no?
Solution 2: Build a new launch/landing site much further north, say at Barrow, Alaska. I mean, the necessary cross-range is dictated by the length of the circle running around the Earth at the latitude of where you want to land, right? And the circle at the latitude of Barrow (71°N) is a lot smaller than the one at the equator -- unless I've messed up the calculation, the Earth would rotate only 500 miles or so underneath a polar orbit launched from Barrow. This is within striking distance of the original Shuttle design's cross-range capability. Cons: Cost of building a second facility, and building it up near Santa Claus where the logistical difficulties would be huge. But I note that the Russians are happy to launch from Plesetsk at 62°N
So what am I missing? That neither option was selected says to me that much smarter people than I ruled them out, or realized instantly that they were stupid (see "Quindar, you silly person!", above) but I don't know why and can't find any discussion of the issue -- the Shuttle histories I've read just say that it needed the cross-range capability to get back to Vandenberg, end of discussion.
Edit: OK, the text filters here are amusing -- I wasn't calling myself a "silly person" in the original draft of this
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#2701 by brahmanknight on 25 Sep, 2012 16:52
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1. Vandenberg launches go to the south, over ocean. No land is flown over.
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#2702 by spacecane on 25 Sep, 2012 18:11
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Barrow, AK wouldn't have been a good place especially if SRBs were involved. Regardless, trying to land there and avoid snowfall wouldn't have been fun either.
From wikipedia:
"Temperatures remain below freezing from early October through late May. The high temperature is above freezing on an average of only 120 days per year, and there are temperatures at or below 0 °F (−18 °C) on an average of 160 days per year.[10] Freezing temperatures, and snowfall, can occur during any month of the year"
I often wonder if the Shuttle would have actually have been economical if not for the two DoD requirements that were never used (cross range for single orbit and payload bay length). -
#2703 by Jim on 25 Sep, 2012 18:51
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I often wonder if the Shuttle would have actually have been economical if not for the two DoD requirements that were never used (cross range for single orbit and payload bay length).
The length requirement wasn't just DOD and it was used on NASA missions among others -
#2704 by wolfpack on 25 Sep, 2012 19:01
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I often wonder if the Shuttle would have actually have been economical if not for the two DoD requirements that were never used (cross range for single orbit and payload bay length).
There's a better thread for that.
http://forum.nasaspaceflight.com/index.php?topic=28474.0
Let's keep this one Q&A about the STS we actually built and used for 30 years. -
#2705 by Quindar Beep on 25 Sep, 2012 20:46
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Both requirements were used frequently. Crossrange was never used "for single orbit" but it was used for nominal entry to increase deorbit opportunities, and for TAL site availability.
That was a case of using what they already had, though, wasn't it? The initial requirement was all Air Force, so far as I understand it, and then once they had it anyway, NASA looked at other things they could so with the capability. Please correct me if I'm wrong.
I suppose my question could be rephrased more succinctly as "What's so great about Vandenberg" that NASA felt they needed to build the Shuttle as they did rather than get them to shift to some other launchpad for military-related missions to polar orbit.
To be precise, what made them decide this way in 1972 or so? Any knowledge gained after that time is unfair 20/20 hindsight
Addressing another reply: As for Barrow, I thought about the weather too and most certainly you could be right. Like I said, though, the Russians launch from Plesetsk, ain't exactly Ft. Lauderdale either. Granting they don't launched manned missions and don't try to land anything there either, but still.... -
#2706 by Jim on 25 Sep, 2012 21:01
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Both requirements were used frequently. Crossrange was never used "for single orbit" but it was used for nominal entry to increase deorbit opportunities, and for TAL site availability.
That was a case of using what they already had, though, wasn't it? The initial requirement was all Air Force, so far as I understand it, and then once they had it anyway, NASA looked at other things they could so with the capability. Please correct me if I'm wrong.
No, NASA agreed it had similar requirement.
From the Space Shuttle Decision:
"In addition, a 15-by-60 foot bay would serve the needs of both agencies by providing room for the space tug and its payloads. Many spacecraft would fly to high orbit, including geosynchronous orbit, and the payload bay had to address such expectations as that future communications satellites would also grow larger. Thus, when Dale Myers asked Grant Hansen to weigh the merits of a reduction to 12 x 40 feet, Hansen replied:
The length of the payload bay is the more critical dimension affecting DOD mission needs. If the payload bay length is reduced to 40 feet, then 71 of the 149 payloads forecasted for the 1981 to 1990 time period in Option C and 129 of the 232 payloads forecasted in Option B of the mission model will require launch vehicles of the Titan III family....
The 15 foot diameter by 60 foot length payload bay size previously stated as the DOD requirement is based upon payloads presently in the inventory, on the potential use of a reusable upper stage to accomplish our high energy missions, and on a capability to provide limited payload growth. This requirement is still considered valid.
In summary, should you elect to develop the shuttle with a 12 ft x 40 ft payload compartment, it will preclude our full use of the potential capability and operational flexibility offered by the shuttle.... Also, if a portion of the present expendable launch vehicle stable must be retained to satisfy some mission requirements, then the potential economic attractiveness and the utility of the shuttle to the DoD is severely diminished." -
#2707 by Quindar Beep on 25 Sep, 2012 21:04
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Both requirements were used frequently. Crossrange was never used "for single orbit" but it was used for nominal entry to increase deorbit opportunities, and for TAL site availability.
That was a case of using what they already had, though, wasn't it? The initial requirement was all Air Force, so far as I understand it, and then once they had it anyway, NASA looked at other things they could so with the capability. Please correct me if I'm wrong.
No, NASA agreed it had similar requirement.
Whoops, we're talking at cross purposes. I meant just the cross-range capability of 1500 miles that the Air Force requested. So far as I know, NASA only wanted 400 and only went along because the White House made it clear they weren't go to get approval for the Shuttle unless they met the USAF's needs too. -
#2708 by Jim on 25 Sep, 2012 21:04
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I suppose my question could be rephrased more succinctly as "What's so great about Vandenberg" that NASA felt they needed to build the Shuttle as they did rather than get them to shift to some other launchpad for military-related missions to polar orbit.
To be precise, what made them decide this way in 1972 or so? Any knowledge gained after that time is unfair 20/20 hindsight
No, it is the other way around.
The final shuttle configuration chosen drove the need to use VAFB for the same reasons that existing launch vehicles used VAFB, no overflight of land during launch.
Back when the shuttle was going to be TSTO RLV, they were looking for other launch sites than KSC. -
#2709 by Oberon_Command on 25 Sep, 2012 21:07
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I suppose my question could be rephrased more succinctly as "What's so great about Vandenberg" that NASA felt they needed to build the Shuttle as they did rather than get them to shift to some other launchpad for military-related missions to polar orbit.
To be precise, what made them decide this way in 1972 or so? Any knowledge gained after that time is unfair 20/20 hindsight
The final shuttle configuration chosen drove the need to use VAFB for the same reasons that existing launch vehicles used VAFB, no overflight of land during launch.
Were there any (alternative) shuttle configurations under consideration prior to the final selection which would not have required the use of VAFB for polar orbit flights? -
#2710 by Jim on 25 Sep, 2012 21:09
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Both requirements were used frequently. Crossrange was never used "for single orbit" but it was used for nominal entry to increase deorbit opportunities, and for TAL site availability.
That was a case of using what they already had, though, wasn't it? The initial requirement was all Air Force, so far as I understand it, and then once they had it anyway, NASA looked at other things they could so with the capability. Please correct me if I'm wrong.
No, NASA agreed it had similar requirement.
Whoops, we're talking at cross purposes. I meant just the cross-range capability of 1500 miles that the Air Force requested. So far as I know, NASA only wanted 400 and only went along because the White House made it clear they weren't go to get approval for the Shuttle unless they met the USAF's needs too.
NASA realized that they would need it too if they were going to launch from VAFB for aborts -
#2711 by Quindar Beep on 25 Sep, 2012 22:06
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Even if that was the case, it wouldn't make your claim (that they "were never used") any less wrong.
Uhhhh...I know that's a common claim, but if you look back you'll see I didn't say that. What I said was that NASA did not originally intend to use it, and that just went with it after it was baked in for other reasons. Really, go lookQuote from: JorgeI'll let the original shuttle program manager (Robert Thompson) do the correcting. Here's his CAIB testimony:
http://caib.nasa.gov/events/public_hearings/20030423/transcript_am.html
Ah! Now that was the sort of thing I was looking for. So they must have changed their ideas between Max Faget's initial design (and the North American Phase A proposal that tried to hit that design on the nose) and 1973. Thanks.
You wouldn't happen to have anything else along those lines, would you?Quote from: JorgeIt was an existing USAF-controlled facility that allowed polar launches without land overflight and was within CONUS for easier logistics. It had the extra benefit (though I don't think this drove the original decision) that the groundtrack for the single-orbit mission never overflew USSR ground stations.
Yeah, I was thinking about that in the context of the Barrow thing...it's not over land for the first bit over the Arctic Ocean, but then it was across the USSR for a long way after that. If aborting to Banjul would have been embarrassing, imagine having to abort to within spitting distance of Baikonur!
(Though if you launched south from Valdez or thereabouts you'd get most of the benefit of being far north, have pretty good logistics by sea, and have nothing but Pacific under you until you were over Antarctica.) -
#2712 by Quindar Beep on 25 Sep, 2012 22:28
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Yikes. You were actually thinking of launching *north* from Barrow!? Never mind abort safety; the *nominal* launch would be headed straight toward the USSR. I can think of a couple more obvious issues with that than abort safety.
So you don't think that putting a big neon sign on the underbelly that read "NOT AN ICBM HONEST" in Russian would work, then? -
#2713 by Jim on 26 Sep, 2012 00:47
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I suppose my question could be rephrased more succinctly as "What's so great about Vandenberg" that NASA felt they needed to build the Shuttle as they did rather than get them to shift to some other launchpad for military-related missions to polar orbit.
To be precise, what made them decide this way in 1972 or so? Any knowledge gained after that time is unfair 20/20 hindsight
The final shuttle configuration chosen drove the need to use VAFB for the same reasons that existing launch vehicles used VAFB, no overflight of land during launch.
Were there any (alternative) shuttle configurations under consideration prior to the final selection which would not have required the use of VAFB for polar orbit flights?
Any of the TSTO RLV vehicles. They didn't require KSC either. -
#2714 by spacecane on 27 Sep, 2012 12:52
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I'm not sure what thread this question should be in. It isn't exclusive to shuttle but applies to shuttle. How do the T-0 umbilical quick releases work?
I have always been fascinated by the fact that a connection can be tight enough to prevent LH2 leaks but release quickly and reliably enough to be pulled away at liftoff. -
#2715 by wolfpack on 27 Sep, 2012 14:17
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I'm not sure what thread this question should be in. It isn't exclusive to shuttle but applies to shuttle. How do the T-0 umbilical quick releases work?
I have always been fascinated by the fact that a connection can be tight enough to prevent LH2 leaks but release quickly and reliably enough to be pulled away at liftoff.
Explosive bolts to the side of the Orbiter, plus cables in high tension attached to the "plates" of the umbilicals, I believe. At T-0 the bolts blow, the cables pull the umbilical plate into to tail service mast, and a very heavy clamshell door falls closed to shield from booster exhaust.
There's a DVD called "Ascent" that has some footage from inside the TSM's.
Also here - -
#2716 by Jim on 27 Sep, 2012 14:24
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Explosive bolts to the side of the Orbiter, plus cables in high tension attached to the "plates" of the umbilicals, I believe. At T-0 the bolts blow, the cables pull the umbilical plate into to tail service mast, and a very heavy clamshell door falls closed to shield from booster exhaust.
Bolts are not always used. LH2 upperstages don't have bolted on carrier plates. The umbilicals use a clamping mechanism that undone by a tension wire that is pulled by either vehicle movement or swing arm retraction. -
#2717 by Go4TLI on 28 Sep, 2012 05:32
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If that's the case, what was it that made the turn around processing take so much longer than the ordiginal plan? Was it just the TPS inspection/repair process?
You had most of it: "inspection, minor repair and refueling" and include testing and payload bay reconfiguring. As part of "refueling" the OMS and RCS pods were removed. As for the middeck, all the lockers and crew accommodations were removed after each flight.
The pods and modules were not removed for a standard flow. They were only removed for OMDP requirements and if there was a significant issue that required an LRU to be replaced.
The pods/modules carried whatever residual prop was in them until they were filled again at the pad. -
#2718 by Jim on 28 Sep, 2012 11:24
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They were only removed for OMDP requirements and if there was a significant issue that required an LRU to be replaced.
OMRSD requirements -
#2719 by Go4TLI on 28 Sep, 2012 11:57
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They were only removed for OMDP requirements and if there was a significant issue that required an LRU to be replaced.
OMRSD requirements
Right, the OMDP requirements in the OMRSD. Otherwise, if an LRU had to be replaced. Otherwise they remained on the vehicle, which was the far majority of the time.
