March 1982:STS-2 mission report

Introduction

The Shuttle's second mission can be regarded as the flight that brought us back to Earth with a bump after the euphoria of STS-1 a year ago. Although as a whole it was successful, the problems which caused the launch delays and the early return from orbit show that the system is still not at operational status. Add on to that the fact that processing between missions is still taking months, rather than weeks, and we have a picture of the Shuttle which may drive more commercial customers back to expendable launch vehicles.

Following Young and Crippen's flight last April, STS-2 was scheduled to go into orbit in late September but a number of delays - the most dramatic arising from the propellant spillage on 22 September - pushed the date into early November. It is exactly this kind of problem that has to be overcome if the Shuttle is to become a regular, reliable stepping-stone into space.

But having said that, STS-2 can be viewed as an overall success, with many of the secondary objectives being achieved. Although this flight was certain to attract less attention than the first (similar to Apollo 12 after the first Moon landing), about a quarter of a million people turned up in the Cape area to witness the second launch attempt. That figure will no doubt drop off for the next few flights but the first time that an Orbiter lands back at the Kennedy Space Center (planned for mission 5) we should see large crowds once more.

Launch

The first attempt on 4 November to leave Pad 39A failed to overcome several problems and NASA officials decided to order a postponement, although subsequent analysis suggested that a launch was possible. The first worry was the weather. For several days the area was under heavy cloud cover and the mission rules stated that it had to be 50% or less (to allow photography and visual observations during the launch). John Young flew around to check the conditions and declared them to be tolerable. Wind speed was quite low, an important factor since the vehicle clears the launch tower by a matter of feet. A large gust at the wrong time and the two could have come into contact. The launch window extended for 4 hours 40 minutes but there was a 50 minute "hole'' to prevent the Sun shining directly into the astronauts' eyes during landing.

The 73 hour countdown began on 31 October and proceeded smoothly but the planned hold at T-9 minutes (the beginning of the computer-controlled automatic sequence) lasted longer than expected because pressure in the oxygen section of the External Tank was low. The countdown continued without a hitch until the computer commanded a hold at T-31 seconds because the oxygen tanks feeding the fuel cells were below pressure. The engineers on (he spot decided that the readings were acceptable but they failed to override the sequencer in time (shades of the late hold during the Apollo 17 launch).

While that difficulty was being overcome, it was noticed that the oil pressures (100 instead of 60 psi) in the Auxiliary Power Units were not normal. The countdown had been recycled to T-9 minutes and then T-20 minutes, with the weather conditions becoming worse all the time. A postponement was called to allow the mystery of the high APU pressures to be solved. The fear was that contamination in the oil would clog filters and prevent the vital lubrication/cooling action from taking place. It was significant that the high pressures were seen in units 1 and 3, which had been left as they were (apart from refuelling) after STS-1, and not unit 2, which was a replacement for a APU that failed on the first mission.

By the time Engle and Truly emerged from Columbia they had been aboard for 5 hours, close to the 6 hour limit set by doctors.

The auxiliary power unit (APU) is a hydrazine-fuelled turbine-driven power unit which generates the mechanical shaft power to a pump that produces pressure for the Orbiter's hydraulic system. Three separate APU's, hydraulic pumps and hydraulic systems, are all located in the section behind the aft bulkhead. The APU's and their fuel systems are isolated from each other so that a single system failure will not affect full operational performance. If two systems fail, the third system will provide sufficient hydraulic power, but at a reduced rate.

Oil samples were taken and analysis showed that the contaminants - caused by some of the hydrazine fuel leaking through and reacting with the oil - would have probably dissolved back into the oil as the units warmed up. In future, NASA will change the lubricant between flights.

The second launch attempt on 12 November faced difficulties of its own. A hold at T-8 hours stretched beyond 13 hours after a multiplexer/demultiplexer aboard Columbia failed. Otherwise, the count proceeded smoothly and the hold at T-9 minutes was extended in order to check everything was running as it should. The flight controllers wanted no more last-second stoppages.

Columbia, weighing 4,474,269 lb, left Pad 39A for the second time at 15.09.59.887 GMT on 14 November - Dick Truly's 44th birthday - with the three main engines and two solid boosters burning well. Seven seconds later, observers could see the vehicle go through a 118 degree roll to take it onto the correct heading as it arced out over the Atlantic on its way to orbit.

The dangerous pressure pulse recorded during the STS-1 booster ignition on the pad was reduced to an acceptable value on this occasion by spraying water into the rocket exhausts and suspending troughs of water below the craft.

Tracking showed that Columbia was climbing more steeply than it should have done - a factor affecting the amount of payload that the Shuttle can carry - at about the same rate as STS-1.

The solid boosters separated at T+2 minutes 10 seconds and the main engines continued to burn until shutdown at 8 minutes 42 seconds when the vehicle was about 60 nm high. The SRB recovery teams had to brave rough seas and the boosters spent longer at sea than the STS-1 pair. Inspection showed there to be about half ay much damage as on the first flight, with the main damage being caused by the nozzle extensions failing to separate before impact. The External Tank jettisoned a few seconds after main engine shutdown, leaving it to tumble slowly (the tumbling mechanism failed on STS-1) down into the Indian Ocean 256 seconds later.

Finally, a 1 minute burn with the OMS engines pushed Columbia into orbit at a speed of 25,667 fps, just 1 fps short of target.

In Orbit

The first signs of serious trouble arose 2 hours after liftoff when the crew reported an increase in the alkaline level of the electrolyte in the number 1 fuel cell. The three cells carried by Columbia provide the entire craft with power and supplement the crews' drinking water supply as a by-product, so any problems with the cells are treated very carefully. Fuel cells have been carried in manned spacecraft since Gemini 5 in 1965 but they have a reputation for being temperamental (as indeed they were in that first mission). Each of the Orbiter cells weigh about 200 lb and sit at the bottom of the cargo bay just behind the pressurised crew compartment. They produce between 2 and 12 kW of power, with any one of them sufficient to run Columbia safely. On this test flight, however, the mission rules were that if only two cells were available then the flight had to be ended short of the planned 124 hours. A series of complicated manoeuvres to gather aerodynamic information during reentry was one of the prime objectives and if a second cell had failed these manoeuvres would have had to be cancelled.

Mission controllers therefore decided to close the unit down and rely on the other two but, instead of chopping the flight back to 54 hours, they continued to aim for the full duration. Flight Director Neil. Hutchison told pressmen gathered in Houston that evening they would continually assess how the mission was going, hoping to gradually extend it to the planned 124 hours. This news was not entirely unexpected because any early curtailment would have brought unjustified bad publicity at a time when the space programme was already suffering severe cutbacks.

But caution won over and it was decided to bring Columbia back early after all. Capcom Sally Ride - a Mission Specialist astronaut who will probably fly on one of the early missions - radioed up to Engle and Truly barely a day after achieving orbit: "Columbia, this is Houston. We have some bad news for you. You're going to be coming home tomorrow." Engle responded, "Oh boy, that's not so good."

Reducing STS-2 to 2 days was not an indication of a failed mission because the experiments had been deliberately planned with the most important sections coming early in the expected 84 revolutions. For example, 12 hours of testing the Remote Manipulator Arm had been spread over three days, with the first session containing the more important exercises. In the end, Engle and Truly managed only a 4 hour work-out but they demonstrated the basic reliability of the system.

The first major action in orbit was to open the cargo bay doors and deploy the radiators which rid Columbia of its waste heat. The flight plan showed the opening taking place less than 11 hours into the mission but Engle and Truly had trouble using the theodolite which detects any distortion in the structure. The crew had to be sure they could close the doors but they delayed for about half an hour while they struggled to see the theodolite targets in the dark cargo bay.

Tests of the Remote Manipulator, although curtailed, showed that the robot arm could operate in space. The most important sequences were deliberately planned to fall within the first day's operations so, although only one-third of the intended time was devoted to arm manipulation, NASA and Canadian planners could go ahead with some confidence on forming more ambitious plans for STS-3.

Truly began unstowing operations about 22 hours after launch, taking the arm out of its cradle down the port side of the cargo bay. He tested the two modes of operation - manual, and the automatic sequence in which the operator punches in the target location and the Orbiter General Purpose Computer moves the arm - and found them to be smooth. In fact, he said the motion was smoother than during the ground simulations. Firing Columbia's main RCS thrusters provided information on how the arm behaved under craft acceleration.

Viewers on the ground were able to see the Orbiter from some unusual positions. So far, we have seen through TV cameras mounted in the crew's cabin or the cargo bay but the Manipulator carries two cameras at the elbow and wrist joints and these were directed towards the astronauts from above and behind as they .stood at the rear facing windows. Truly responded by holding a sign up bearing the words "Hi, Mom", rather reminiscent of the Apollo 7 crew's "Keep those cards and letters coming in folks" some 13 years before. These cameras promise exciting pictures when the arm is actually used for deploying and retrieving satellites.

As the arm was being stowed back in its cradle, a back-up drive mode (in which the three joints are moved one at a time) failed and Truly had to go back to a primary mode. The TV cameras also failed after an electrical fault, but neither problem was considered to be major.

Back to Earth

The reentry of Columbia was perhaps the most important part of the whole mission since Engle and Truly planned to execute no less than 19 groups of manoeuvres designed to extend our knowledge of the aerodynamic qualities of the craft. Planners expected that there might not have been enough time to perform them all but they were all achieved - an accomplishment tempered somewhat by the discovery that a flight recorder (some were carried out during radio blackout so no telemetry could be transmitted to ground recorders) had failed and some of the data was lost.

An hour before the deorbit burn over the Pacific Ocean, the two astronauts were advised to land on Runway 15 at Edwards after John Young had tested the landing conditions and found them to be suitable for a touchdown with the wind blowing across their path. This is an important requirement for qualifying the craft to land on the strip at KSC. But Young later found the winds to be close to the tolerance limit and a switch was made back to Runway 23 for a landing into the wind. These different approaches were already plotted in Columbia's computers and it was a relatively simple procedure to switch from one to the other.

Engle took over control as Columbia began its turn to sweep around the 20,000 ft diameter Heading Alignment Cylinder 40,000 ft high to head back towards Runway 23. He actually cut inside the intended arc in order to keep the acceleration below 2g (the original plan was to fly around the HAC automatically but John Young found that the wind speed might have been too high).

The new Autoland system took over at 18,000 ft, using data from the MSBLS (Microwave Scanning Beam Landing System) to bring the craft down to 2,000 ft. As it came into play, it ordered a slight upward angle to bring the flight path back up to its correct altitude. Engle took over at 2,000 ft and flared the path out to a landing at about 195 knots, slightly short of the target but acceptable because of the strong headwinds.

The first of the servicing vehicles was in position 5 minutes later, with ground crews searching the area for dangerous gases and liquids. Initial inspection of the tiles showed there to be much less damage than after the first flight, with perhaps the number needing replacement in the low tens. One surprise was that two new types of damage were found: some tiles had their upper surfaces torn away, and blistering occurred near the body flap at Columbia's rear.

STS-3 and After

Commander of the 7-day third Shuttle flight will be Jack Lousma who last went into space in the second Skylab mission in 1973. His pilot will be Cordon Fullerton who will thus become the third member (the first two being Crippen and Truly) of the Group 7 ex-Manned Orbiting Laboratory astronauts to fly.

The crewing policy is clearly one of combining an experienced man with a later astronaut. Engle was commander on his first mission but he was,nonetheless, one of the best men available. The Group 7 men (transfered to NASA in 1969) will command their own missions later - the first being Crippen - with, probably, some of the new Group 8 pilots under their command.

STS-1 Young/Crippen (Groups 2/7) .

STS-2 Engle/Truly (Groups 5/7)

STS-3 Lousma/Fullerton (Groups 5/7)

The first four flight crews announced in April 1978 allocated astronauts Haise/Lousma and Brand/Fullerton to the third and fourth missions, respectively. Haise left NASA in June 1979, leaving Lousma to take over the commander's seat for that flight. STS-5 will also carry two mission specialists, making it the first four-man spacecraft.