Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!henry From: henry@utzoo.UUCP (Henry Spencer) Newsgroups: net.columbia Subject: AW&ST on 51L Message-ID: <6511@utzoo.UUCP> Date: Fri, 14-Mar-86 14:07:06 EST Article-I.D.: utzoo.6511 Posted: Fri Mar 14 14:07:06 1986 Date-Received: Fri, 14-Mar-86 14:07:06 EST Organization: U of Toronto Zoology Lines: 103 Since nobody has been posting this stuff, and I suspect a lot of people don't have easy access to Aviation Week and Space Technology, herewith some info from recent issues. The Feb 17 issue contains a full-page photo which just about resolves the problem at a glance. It's yet another photo of the mess just after the explosion, but this one is taken from a revealing angle. You can clearly see that the starboard SRB is trailing a *second* plume of exhaust from its side. Furthermore, on looking closely, the nose of that SRB is damaged and its recovery chutes are falling out. This considerably strengthens the theory that the bottom attachment point broke loose and the top of the SRB pivoted into the tank; one would expect the SRB nose to be damaged then. The Feb 24 issue (the latest I have -- long propagation delays) has a photo clearly showing the puff of black smoke just after liftoff. It also mentions that the primary seal is normally pushed out of its seat by a seal integrity test during booster assembly; it is pushed back into place by motor pressure after ignition! The secondary seal has to hold things together until the primary seal seats itself. But at 0.6 seconds after ignition, deflection of the motor structure is expected to unseat the secondary seal! If the primary seal is slow in seating (e.g. because it's cold and stiff), and the secondary seal unseats, you might well get a puff of black smoke, implying serious erosion of the seals and burning of the grease and putty in the joint. Then the primary seal would finally seat, sealing the joint... for the moment, until the damaged primary seal wears down and the stresses from wind shear and dynamic pressure flex the joint. There are also some other tracking photos supporting various aspects of the following timeline, mostly derived from telemetry (times are in seconds from nominal launch): 0.0587 SRBs lit. Liftoff. 0.445 Black smoke at or near aft joint on right SRB. 12 Last black smoke. Roll maneuver underway. 20.084 Throttle-back begins. 40 Guidance reacts to a wind shear. 58.774 Black smoke again. 59 Maximum dynamic pressure. 59.249 Flame plume from side of right booster. 60.164 Right booster's internal pressure starts to diverge from that of left booster. Flame plume growing. 62.484 Right outboard elevon commanded to move. Some main-engine gimballing in next three seconds. These events probably due to winds rather than to the booster failure. 66.174 Bright spots of fire on top (side nearest orbiter) of right booster. Joint rupture spreading? 66.484 Liquid hydrogen pressure in external tank anomalous. 67.684 Pressure-change rate in liquid oxygen inlet altering. Possibly result of completion of throttle-up. 72.141 Shit hits fan. Vehicle tugged to right at 0.227 G. Lower attach point of right booster has failed? 72.201 Rate gyros on right booster indicate lower attach point failure, lower end moving outward, upper end moving inward toward tank. 72.281 Rate gyros indicate outward motion of aft end of booster complicated by "upward" motion towards orbiter. This would explain the charring of the aft right portions of the orbiter. Booster may even have struck, perhaps severed, the right wing. 72.661 Vehicle yawing to left, acceleration 0.254 G. 72.884 Inlet pressures to main engines dropping. Tank rupture by nose of booster underway? Feed lines severed? 73.044 Right booster pressure down 24 psi below left booster. Data is still coming because the data lines run through the upper attach point, which is still intact. 73.175 Massive cloud of oxygen or hydrogen gas streaming aft along tank from rupture caused by booster nose. [This is visible in one of the photos AW&ST has printed.] Some gas at bottom of tank too; tank starting to break up? 73.200 Flash of fire under nose of orbiter. 73.226 Powerful explosion near right forward booster attach point, presumably due to propellants from ruptured tank mixing. 73.399 Massive disturbances in main-engine propellant flow. Hydrogen turbopumps approach red-line limits. External tank exploding. 73.534 No. 1 main engine shuts down due to propellant-flow disturbances. 73.605 Telemetry stops. -- Henry Spencer @ U of Toronto Zoology {allegra,ihnp4,linus,decvax}!utzoo!henry