Tuesday, December 2, 2008

Endeavour's Hypersonic Return

Endeavour's Hypersonic Return: "blog post photo

NASA /Dryden Photo

The shuttle mission STS-126 pilots flew Endeavour through a hypersonic reentry and somewhat more challenging landing approach than normal, to bring their crew back to Edwards AFB Calif. Nov. 30 with a touchdown at 1:25 p.m. PST.'

'Poor weather at Kennedy thwarted two opportunities to land there Nov. 30, as well as any chance of getting into KSC on Dec. 1, when similar bad weather is forecast.'

Mission commander Navy Capt Chris Ferguson and pilot USAF Col. Eric Boe modified their use of manual and autopilot control to manage the orbiter’s energy state,' as needed,' to fly a 340 deg. left overhead turn above Runway 04 at Edwards to align with the runway approach path as the vehicle was slowing below Mach 1.'

Overhead turns of that magnitude—nearly a complete descending circle--with the 100 ton glider to align with the runway are relatively rare. '' It is no big issue for a powered aircraft, but with no power, the maneuver required that the auto system ensure Endeavour arrived at Edwards---after a nearly 4,600 mi. hypersonic glide from the 400,000 ft. atmospheric interface-- with enough energy ‘in the bag’' to spend if necessary to stay on the proper 290-300 kt. airspeed and on course in the turn.'

Likewise the vehicle could not be carrying too much energy' that would brings its own trouble on how to dissipate it while also landing on Runway 04.' Flight controllers and Ferguson discussed this prior to the reentry, then again in the approach to Edwards. 'Mission Control advised the crew to expect as much as a 4,000 ft.' ‘energy dump’ pitch up maneuver by the autosystem,' or a 1,100 ft. pitch down maneuver to pick up energy, when following the computer projected Heading Alignment Circle (HAC)' display on the instrument panel and head up displays.''

Ferguson let the auto system bring Endeavour onto the HAC, a flight phase where shuttle pilots like to do manual control.' But in this case,' Endeavour and her computers were better at managing the energy via the auto system.'

'He then took manual control to complete the steep approach to landing with smooth and perfectly aligned touchdown 2,000 ft. down the runway going about 300 kt., perhaps 10 kt. faster than other landings (if those speeds put out by public affairs are accurate) How the added energy maneuvers played in, if at all will be discussed in post flight briefings.

blog post photo
'NASA / Dryden Photo

' Launched Nov. 14 with 12 tons of logistics including a water reprocessing system capable of enlarging the station crew size to 6, the STS-126 crew also performed a Herculean lubrication job of the ISS starboard solar array alpha joint. T

hat work alone might be good enough to bypass more extensive repairs later that have been forecast to require as many as 10 previously unplanned extravehicular activities (EVA).'

'The crew spent 16 days aloft and flew a total of 6.6 million mi., nearly 7 days of it docked to the station.

' When weather at Kennedy was clearly not going to cooperate, the Mission Control team headed by Reentry Flight Director Bryan Lunney set up' for a reentry burn at 12:20 p.m. PST (3:20 p.m. EST) in darkness 'over the Southern Indian Ocean leading to an Edwards AFB landing at 1:25 p.m. PST (4:25 p.m. EST). Astronaut USAF Col. (Ret) Pam Melroy, a shuttle commander herself, 'flew steep shuttle approaches at Edwards in a Gulfstream 2 Shuttle Training Aircraft. She began those flights at about 9:30 a.m. PST.''

Melroy was in touch with the astronaut weather communicator in Mission Control to makes inputs relative to the turbulence and the effects of winds aloft at different altitudes above Edwards.' It was the winds aloft situation and' 340 deg. turn to reach Runway 04 that dominated conversations going into the reentry maneuver north of Madagascar where the two Orbital Maneuvering System engines were fired for 2 min. 54 sec.

''As on all shuttle reentries Endeavour' flew a series of roll reversals' for navigation and guidance' ranging' back to Edwards at' bank angles of up to 80 deg. to kill off lift from the wings. This was so' the vehicle would fall into the atmosphere more efficiently and therefore slow more efficiently for the thermal protection system to dissipate reentry heating.'

'The initial set up required that Endeavour hold 80 deg. of left bank for several 'minutes into the reentry to kill off 170 naut. mi. north crossrange in the initial phase of the glide down from the 400,000 ft. reentry interface point more than 4,000 naut. mi. from Edwards.'When velocity has decreased from 25,000 fps to 19,800 fps. the guidance and navigation system flew a roll reversal to 61 deg. of right bank.' That was held until Endeavour had slowed to 11,000 fps.

The auto system then rolled again this time from right to left. It commanded one more bank maneuver back to the right as Endeavour slowed to 4,100 fps a maneuver clearly visible to tracking cameras at Edwards.' Endeavour' was targeted to land on Edward’s temporary runway 04, a 12,000 ft. long 200 ft. wide 'black asphalt surfaced runway with 1,000 ft. overruns at each end. It is being used until the main Edwards paved runway upgrade has been completed and shuttle landing aids have been reinstalled on it.'But it was no problem to Ferguson and Boe.''

Although winds were light at Edwards, Mission Control told Ferguson that based on Melroy’s findings in the STA and a final weather balloon launch set for when Endeavour was going into the reentry burn, 'they might have asked him to redesignate Endeavour’s navigation and guidance system to fly the orbiter to the approach end of Runway 22, the reciprocal of 04.''

That was not needed but Ferguson was ready to do at Mach 18 if necessary.'It was ironic that Endeavour Reentry Flight Director Lunney was making key space shuttle vehicle decisions in Mission Control ---nearly 40 years to the week, after his father, retired NASA Flight Director Glynn S. Lunney,' was preparing to make critical decisions as a Flight Director for Apollo 8, the first manned flight to orbit the Moon launched 40 years ago in December, 1968.'The ISS itself today has a new guest.

'The Progress 31 spacecraft was docked to the station’s nadir facing Russian port, using a manual fly in by the crew at 6:25 a.m. EST after problems arose with the' automatic system.' Progress 31 brought 2,866 lb. of spare parts, 1,918 lb. of propellant 110 lb. of oxygen and 463 lb. of water.


(Via On Space.)

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