Xref: utzoo sci.aeronautics:100 sci.space:14435 sci.space.shuttle:3727 Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!ames!skipper!shafer From: shafer@elxsi.dfrf.nasa.gov (Mary Shafer) Newsgroups: sci.aeronautics,sci.space,sci.space.shuttle Subject: Re: X-30, Space Station Strangles NASP Message-ID: Date: 6 Oct 89 15:08:40 GMT References: <5292@eos.UUCP> <4983@omepd.UUCP> <6430@quick.COM> Sender: news@skipper.dfrf.nasa.gov Organization: NASA Dryden, Edwards, Cal. Lines: 72 In-reply-to: srg@quick.COM's message of 5 Oct 89 22:23:37 GMT In article <6430@quick.COM> srg@quick.COM (Spencer Garrett) writes: In article , shafer@elxsi.dfrf.nasa.gov (Mary Shafer) writes: -> -> The shuttle comes in from the north to north east. It comes "feet -> dry" at about Mach 7 and 145K ft, it's overhead at Edwards at Mach 1 -> at about 40K ft. It does a HAC (Heading Alignment Circle) to put it -> on the runway heading (usually 17 or 22), so essentially the pattern -> is about a 270 teardrop with a longish final. I think it's a 20 deg -> glidepath, with a fairly short flair. Final is flown at 285 KEAS, -> gear deployed at 275 KEAS, touchdown at 185 KEAS. (I'm taking these -> figures from Young and Crippen's 1981 SETP paper on STS-1, so the -> speeds may not be exact for any given mission, but they're about -> right.) Um, I believe that should be *towards* N-NE. I meant from West to North-West. The orbits aren't equatorial. (I think the angle of inclination can be over 40 deg, but I don't have one of the ground-track maps to confirm this.) They usually land on 17 or 22, although they have landed on 15. The Shuttle uses *two* glidepaths on final. They fly most of the approach on a 17 degree (as I recall) glideslope, then make an abrupt pitch up to the normal 3 degree glideslope. It looks like the two intersect right off the end of the runway (where "right off" may be a mile or two at these speeds) and they only spend a few seconds (10 or 15?) on the 3 degree slope before starting the flare. They come around the HAC (heading alignment circle) and aim at a point on the lakebed about 1 mi before the touchdown point. This point is identified by a big X in black paint and a set of directional lights. (Actually they're narrowish spotlights.) This first portion, known appropriately as "final", is about a 20 deg glide slope. When they get fairly close to the ground they "flare" to a 3 deg glide slope, using the ball and bar beside the runway. Now for the questions! Is "coming feet dry" the same as extending the landing gear? I'm pretty sure I remember seeing the gear pop out *after* the flare, and I can't imagine having to design gear (much less gear doors) that could handle Mach 7! Coming "feet dry" means coming over dry land at the coastline. (I've been talking with too many Navy attack pilots. Sorry.) You're right about the gear; they pop it at about 150 ft AGL, maybe lower. It _always_ looks like they've left it until too late. And what's the "E" in KEAS? Surely Edwards doesn't have its own standard of measurement! :-} Equivalent. Ve = Vt * sqrt(rho/rhosl), where Ve is equivalent velocity, Vt true velocity, rho density at altitude, rhosl sea level density. (I need subscripts!) At sea level, Ve = Vt. In fact, at Edwards Ve pretty much equals Vt. However, at 40 K ft .... My Flight Test Engineer's Handbook says that Ve is frequently used for piston-engined aircraft (because it's a direct function of dynamic pressure, or qbar). We don't use it commonly here at Dryden, but we do use qbar itself. Since qbar is a primary measurement it's more sensible to use it, rather than Ve, which is a derived term. We mostly fly fighters and other military aircraft so we use KIAS or KCAS for airspeed. Is anybody interested in how and why we instrument our research aircraft? If so, I'll write something. -- Mary Shafer shafer@elxsi.dfrf.nasa.gov ames!elxsi.dfrf.nasa.gov!shafer NASA Ames-Dryden Flight Research Facility, Edwards, CA Of course I don't speak for NASA