Space Tailors Sew a Fine Seam. TECHNOLOGY: ORBITER INSULATION. Stitches and knots must be perfect for thermal coverings used on the space shuttle

NEEDLES. Straight pins. Thread. Sewing machines. Seam rippers. You'd expect to see all these in a tailor's shop. What are they doing in a space shuttle factory? Such sewing tools are used by thermal protection system mechanics at the Kennedy Space Center in Florida to make heat-resistant flexible insulation blankets for space shuttle orbiters. The mechanics tailor the blankets from fiberglass cloth or metal-coated mylar. They work from multi-page patterns, often stitching by hand to make coverings of all shapes and sizes that fit precisely into pre-measured spaces on the fuselage or in the payload bay of each orbiter.

Few of the mechanics have professional garmentmaking experience, but many are women who enjoy sewing as a hobby. For most, the similarities between sewing at home and sewing at work stop with the needles and thread: A missed stitch or a crooked seam in your hand-made shirt may be no big deal, but on the space shuttle it could be disastrous. The blankets help keep an orbiter from melting as it reenters earth's atmosphere after a trip in space.

That's why the blankets must be sewn precisely. Sewing for the space shuttle is not easy. No Simplicity tissue-paper patterns here, says technician David Sheets.

``The drawing itself is only three pages long,'' Mr. Sheets says, fingering a blanket blueprint as he counts. ``Then you've got 1, 2, 6, 7, 8, 9, nine, 10, 14 pages of engineering changes.'' Sheets and his co-workers must make plastic patterns from the blueprints supplied by their employer, Rockwell International.

Learning to read the blueprints is as difficult as sewing the blankets, says Sheets. ``For me, it took about three or four years to really, completely understand them. And I still see stuff all the time that I don't know.''

For more than an hour, Linda Wirtzberger has been following a blueprint that tells her how many hand stitches to make on a gap-filler about the size of an open wallet. She wears gloves and a white cotton smock to protect the heat-cleaned and waterproofed material from oil in her hands.

``Everything is written in our blueprints as to how we do it. All the stitches have to be a certain dimension,'' says Ms. Wirtzberger, a technician since 1979 who moonlights as an upholsterer. ``Our blueprints will tell us six to eight stitches per inch, a knot has to be placed every inch, it has to be sewn with a certain type of thread, or it has to be tied off in a certain way.''

Wearing a similar smock and gloves, Marie Smith is tying knots on every square inch of a rectangular quilt 4 inches wide and 18 inches long. Her small piece will fit on the midbody of Orbiter Columbia, scheduled to fly in July.

Like Wirtzberger, Ms. Smith has been sewing for the space shuttle for nearly 10 years. She can make one or two of these blankets a day - three or four if she is making ``regular square'' ones. There are about 2,300 blankets on each orbiter, and no two are exactly alike.

Smith describes her job as ``fantastic'' despite its tedium.

``When you sit here and do all this by hand, to see it bonded on the ship and going up, it's exciting when you know you did it with your own two hands,'' Smith says.

``Every stitch on each blanket is checked and rechecked for quality,'' says Connie Weatherby, a technician who's been on the job since October. She is ripping out a machine stitch made on a silvery pad that will fit inside Columbia's payload bay.

``They check our measurements and they check our after-product, and they're supposed to watch us work,'' says Ms. Weatherby, who makes most of the clothes she wears. Even though no one is watching over her shoulder right now, she is redoing her work, because she isn't satisfied.

A quality-control inspector ``wouldn't have known that the machine stitching had balled up on the bottom. That's why I'm supposed to feel comfortable with it,'' Weatherby says. ``Whenever you're sewing something, you want to make sure you have a good stitch.''

For Weatherby and many of her co-workers, knowing their hands have touched the shuttle is half the fun of getting paid.

``The job's got a lot of short-term and long-term benefits,'' says another technician, Howard Baker.

``You get to jump up and down every time there's a launch. You're able to do something for your country and have a good job, too, and that's hard to beat.''