Newsgroups: sci.space.shuttle
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: Built-in delays & 51-L meaning
Message-ID: <1988Oct1.230954.11578@utzoo.uucp>
Organization: U of Toronto Zoology
References: <852@scubed.UUCP>
Date: Sat, 1 Oct 88 23:09:54 GMT

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