nobody@scubed.UUCP (anonymous NFS user) (10/01/88)
Well, I recall seeing the question asked awhile back, but I don't recall any explanations. I tried a pattern search on "delay" on read articles but didn't find any. Apologies if I simply missed the answer. Anyhoo, I'll try posing the question again in the hope of a knowledgable response. What is the purpose of built-in delays in the countdown? On the surface, it seems to make the "countdown" kind of a silly formality. Understood, we wouldn't want to deprive everyone of the chanting ritual and all. There are, no doubt, milestones along the timeline and systems coordination considerations, but still it seems realistic to think that they (NASA) could simply say, "...OK, any objections?...everybody ready?...3-2-1 GO!!!" Next question. Can someone explain the significance of the mission designation numbers? By now, the Challenger flight is engrained in all our memories as mission "51-L" and "STS-26" (26?...well, so much for engrained). I know that "STS" stands for "Space Transportation System" or some such and that "26" designates the count of missions, but what do "51" and "L" stand for? Henry Spencer are you out there? See what happens when you're so knowledgable?
jay@ncspm.ncsu.edu (Jay C. Smith) (10/02/88)
In article <852@scubed.UUCP> rankin@scubed.arpa (Tom Rankin) writes: >What is the purpose of built-in delays in the countdown? It is my understanding that the countdown represents progress toward the launch. Before the launch there are times when there is progress made (and the countdown clock is running), and there are times when everything stops and checks and doublechecks on the progression so far and the upcoming progression are made (that's the hold). It may seem silly, but it's really not. It's analogous to an expedition to the top of Mt. Everest -- one doesn't just go all the way up from the base without stopping. >I know that "STS" stands for "Space Transportation >System" or some such and that "26" designates the count of missions, >but what do "51" and "L" stand for? STS-51L was actually the 25th mission. It works like this: 5 The year, as in 198*5*. Yeah, that's right, it went up in '86, but it was originally planned for '85. In fact, some previous flights got out of order in this respect (was the mission before 51L a 6?). 1 The launch site number, in this case Kennedy Space Center. The only other launch site was 2, Vandenberg AFB in California, but it was never used, and probably never will be now. L The particular mission. Originally alphabetized in the initial planning, these could easily rearranged or even dropped as schedules were shuffled. L could have the same meaning that 12 might have, see? Of course, I think NASA only went to this obscure mission designation system to avoid the dreaded STS-13. Since that mission has passed, because there was a major break in mission continuity (great understatement, huh?), and the need to give a launch site designation is gone, NASA has gone back to the old consecutive number system. My question now is: does their internal mission numbering correspond to this, or do they still use another system so that STS-30 won't fly before STS-29? -- "I don't suppose you have any idea what the damn thing is, huh?" --------------------------------------------------------------------- Jay C. Smith uucp: ...!mcnc!ncsuvx!ncspm!jay Domain: jay@ncspm.ncsu.edu internet: jay%ncspm@ncsuvx.ncsu.edu
henry@utzoo.uucp (Henry Spencer) (10/02/88)
In article <852@scubed.UUCP> rankin@scubed.arpa (Tom Rankin) writes: >What is the purpose of built-in delays in the countdown? ... It's basically a silly convention that has evolved over the years, of providing slack time (in case of trouble) as holds rather than as part of the count sequence. >... Can someone explain the significance of the mission designation numbers? [Eugene, if you don't post those answers-to-frequently-asked-questions soon, we're going to end up answering all of them separately anyway!!] NASA originally started numbering shuttle missions sequentially, but this started to cause confusion when changes were made and the order of missions got fouled up. NASA switched to a code system in which the first digit was the last digit of the fiscal year in which the mission was funded, the second digit was which launch site it was to be flown from (1 = Cape Canaveral, 2 = Vandenberg), and the letter distinguished between different missions. So 51L, the last flight of Challenger, was mission L of fiscal year 1985 for launch from the Cape. It may or may not be accidental that the switch to the code system prevented any mission from being designated STS-13. NASA has now gone back to sequential numbering, for now at least: the first post-Challenger mission is STS-26. -- The meek can have the Earth; | Henry Spencer at U of Toronto Zoology the rest of us have other plans.|uunet!attcan!utzoo!henry henry@zoo.toronto.edu
jay@ncspm.ncsu.edu (Jay C. Smith) (10/04/88)
In article <1310@ncspm.ncsu.edu> I wrote: >5 The year, as in 198*5*. Yeah, that's right, it went up in '86, but it > was originally planned for '85. In fact, some previous flights got out > of order in this respect (was the mission before 51L a 6?). Henry Spencer got more specific than I when he pointed out that the year represented the fiscal year in which the shuttle was funded (they begin in October). The three missions preceeding 51L were actually 61A, 61B, and 61C. >My question now is: does their internal mission >numbering correspond to this, or do they still use another system so that >STS-30 won't fly before STS-29? No sooner had I asked this than I read a magazine article telling me that Columbia's return to space as STS-28 is now slated to take place six week's AFTER February's STS-29 Discovery mission. Has something to do with concern over the tight launch schedule for STS-30, which will be launching the Magellan probe. -- "I don't suppose you have any idea what the damn thing is, huh?" --------------------------------------------------------------------- Jay C. Smith uucp: ...!mcnc!ncsuvx!ncspm!jay Domain: jay@ncspm.ncsu.edu internet: jay%ncspm@ncsuvx.ncsu.edu