Space

Discovery lifted off Pad 39B with all three SSMEs at 100% thrust, throttled up to 104% thrust as the vehicle cleared the tower. The vehicle launch weight of 4. 52m lb (2. 05m kg) was one of the highest ever flown. After 7 seconds the vehicle entered a 120° right roll to align the flightpath for an orbit inclined 28. 5° to the equator. Twenty seven seconds into the flight, at 8,000ft, the SSMĖS were throttled back to 65% to reduce acceleration as Mach 1 was approached, after which the computers automatically throttled back up to 104%, 59 seconds into the ascent. The Solid Rocket Boosters were jettisoned two minutes into the flight, after the vehicle passed 125,000ft at Mach 4. After SRB separation, the vehicle flew a steeper ‘abort’ trajectory rather than the previously favoured maximum payload to orbit trajectory. The new trajectory serves to gain as much altitude as soon as possible to allow an abort-once-around (AOA) landing at Edwards AFB in the event of a single SSME failure, the alternative is a transatlantic abort (TAL) if the failure occurs earlier in the ascent, or a return-to-launch-site (RTLS) abort using the Kennedy runway after a hypersonic U-turn.

Mission aborts have been debated heavily since the Challenger disaster. There are some phases of the ascent, termed ‘black zones’, during which a two engine failure will cause the vehicle to fall into the atmosphere and break up regardless of vehicle manoeuvres, while some single engine failure situations would require running the engines beyond with the inevitable risk of explosion, if a TAL abort is to be achieved. The NASA policy at the time of Mission 26 preferred reaching a TAL site under these conditions even if a glide/bailout is feasible earlier. The ability of a crew to survive many hours in the mid Atlantic with survival gear only was seen to be questionable. A decision to ball out must take place before 60,000ft at which point new flight control software will automatically hold the orbiter in a 185-195kt near to minimum sink rate glide. At 40,000ft the cabin would be depressurised, at 31,000ft the hatch blown off and the escape pole deployed. The crew would then attach clips to the pole and bail out in 15sec intervals, to land cca 1nm apart. The crew wear partial pressure g-suits (which double up as survival suits), parachutes and inflatable rafts. The primary task of Mission 26 was the deployment of the TDRS/Inertial Upper Stage vehicle which took place 6:13hr into the mission. The TDRS successfully boosted to geosynchronous orbit although some difficulties were later encountered with a jammed antenna mount boom.

The mission was completed after 64 orbits when the vehicle landed at Edwards Runway 17. Three major equipment problems were encountered with a Ku band TDRS tracking antenna steering mechanism failling, an OMS actuator backup command circuit failing and the flash evaporator avionic cooling system misbehaving. The latter device cools avionics by absorbing heat from freon liquid cooling loops and evaporating (boiling) water, it is used while the vehicle is ascending and descending with its payload doors closed. The inside of the payload doors mount radiators which cool the avionics in orbit. The flash evaporator shut down during insertion to orbit due to suspected icing, it was flushed several times during the hours preceding re-entry and apparently behaved properly during the descent.

Vehicle descent commenced with a 2:50min/12,000lb OMS deorbit burn south east of Madagascar, placing the vehicle in a 178 x 163nm orbit, during which the orbiter descended to its 400,000ft/4,100nm ‘entry interface’ where it enters the upper atmosphere. At this point the orbiter assumed 40° AOA for reentry. Two bank manoeuvres were carried out shortly after to align the flightpath with the proper ground track. Passing through 200,000ft/Mach 15 the vehicle then reversed its bank to 64° right cca 760nm from Edwards. Voice contact with Mission Control was re-established via Vandenberg AFB at 180,000ft/480nm. Descending further, the vehicle software again reversed the roll to 40° left at 155,000ft/270nm, the Californian coast was crossed at 120,000ft/Mach 5. One hundred nautical miles from Edwards the orbiter entered its final high speed manoeuvre banking 36° right at Mach 3. 5/100,000ft after which it descended to entry on final. Assisted by projected HUD steering data, pilots Frederick Hauck (USN) and Richard Covey (USAF) then flew the vehicle to the intercept point for final, where Hauck steered the orbiter onto the 290kt/19o outer glideslope.

At 1,750ft AGL Hauck carried out a preflare pullup to transition to a 1. 5° glideslope, touching down at 200kt with a gentle flare. NASA was back in the space race.

Mission 26 crew have commented since that the orbiter’s systems behaved surprisingly well with nearly all problems associated with equipment modified prior to the mission. All eleven experiments carried out during the mission exceeded expectations while the crew took a large number of photographs from orbit. Concern was expressed at the amount of environmental damage clearly discernable from orbit, with forest fires clearly visible over large areas of South America and Southern Africa.

Discovery will fly its next mission in February this year if the Atlantis Mission 27 can take place as scheduled in late November.

In an unrelated event, the win in the US Presidential election by the Bush/Quayle Republican team is likely to be welcomed by most space/defence contractors, given the Republicans’ strong support for NASA and the somewhat controversial Strategic Defence Initiative. Given the financial pressures resulting from the deficit and foreign debt, it remains to be seen how far the new administration will go in backing its pre-election rhetoric.

Soviet Shuttle-Ski Flies After Initial Launch Deferment.

The first launch of Russia’s new shuttle orbiter Burya, piggybacked on an Energia heavy lift booster, has proceeded without incident after an initial delay. In an unusual move probably inspired by the current Glasnost public relations campaign, the vehicle was revealed to Western media in early October. US observers have commented on a more than superficial similarity between the Russian and US vehicles.

The Russian orbiter carries only OMS engines and is thus shorter and narrower in the tail, its main engines are expendable one-shots on the main tank of the Energia booster.