Successful Mission

In general, only minor problems marred Challenger's second mission. The new text and graphics system, akin to an onboard fax machine, failed after printing a single page and the urine flow system proved erratic on the toilet. On the evening of June 20th, a Cathode Ray Tube (CRT) display on the flight deck went blank and refused to respond to tests, although, fortunately, it was not needed during re-entry. Post-flight analysis confirmed a power supply failure had occurred and corrective measures were put in place prior to STS-8.

One of the more worrying problems was a four millimetre pit in one of the Shuttle's six forward flight deck windows; caused, it turned out, by the impact of a piece of 'space debris'. First reported by the astronauts on June 20th, it became the subject of detailed energy discursive X-ray analysis after landing. Titanium oxide and small quantities of aluminium, carbon and potassium were found in addition to pit glass. The morphology of the impact was suggestive of an impacting particle - most likely a tiny fleck of paint - just 0.2 mm in diameter, travelling at six kilometres per second!

The six windows wrapped around the orbiter's cockpit represented the thickest ever manufactured as optical quality view ports, each consisting of no fewer than three individual layers. The innermost pane, measuring 15.8 mm thick and made from tempered alumino-silicate glass, helped to maintain the cabin's pressure. Next came a 3.3 cm thick sheet of low-expansion, fused-silica glass to provide high optical quality and excellent thermal shock resistance. Lastly, came the 15.8 mm thick outermost pane, also of fused silica, but containing a high-efficiency, anti-reflection coating and capable of withstanding temperature extremes up to 420 degrees Celsius.

It was fortunate that Challenger's windows were thus equipped with these three layers, for the outermost pane - primarily employed to provide thermal protection during the later stages of atmospheric re-entry - was the only one affected by the pit. However, post-flight inspections noted that significant structural weaknesses caused to the outermost panes by such minutely sized debris particles could lead to further problems during a particularly harsh re-entry.

Additionally, NASA's mission report added that more debris damage was experienced generally by Challenger's thermal protection system on STS-7 than any previous Shuttle flight. The damage was close to the left 'chine' - between the leading edge of the left wing and the main fuselage - and was caused, apparently, during ascent on June 18th, as breakaway foam and ice tumbled from the External Tank. More discolouration of her insulating blanketing was evident, compared with STS-6, and several tiles were lost, including a fragment from one belonging to the left main landing gear door.

Originally, STS-7 was scheduled to perform the first Shuttle landing at the Kennedy Space Center (KSC), a fact highlighted in the mission's press kit, which would have helped to reduce turnaround times significantly. "We were looking forward to that," remembered Sally Ride. "They had a red carpet ready to roll out for us and our families were all waiting for us in Florida." Unfortunately, the touchdown on June 24th, due to occur on Challenger's 96th orbit, was postponed by two further revolutions in the hope that conditions would improve or facilitate a landing attempt in California.

It was expected that bringing each Shuttle mission back home to the East Coast launch site would save around one million dollars and five days' worth of processing for the next flight. Moreover, KSC landings would remove the necessity to expose the two-billion-dollar orbiter to the uncertainties and potential dangers of a cross-country ferry flight from Edwards Air Force Base in California atop NASA's heavily modified Boeing 747. However, as Crippen's crew discovered that June day in 1982, the West Coast landing site exhibited far more stable weather conditions than Florida.

The KSC runway, known as the Shuttle Landing Facility (SLF), opened in 1976 and is located a few kilometres north-west of the VAB. Measuring 4.6 km long and 91 m wide, with 300 m overruns at each end, it is all concrete and slopes slightly from the centreline to facilitate drainage. In contrast, Edwards has a multitude of runways: several dry lakebeds and one concrete strip, the largest of which was over 12 km long. Much of the increased size of these runways became necessary not in view of the orbiter's size, but in view of its touchdown speed - roughly 350km/h - and the consequent need for additional margins of safety.

Challenger touches down at Edwards Air Force Base on June 24th 1983.

Two options were available to Shuttle crews returning to KSC: they could either approach from the south-eastern 'end' of the landing strip, designated 'Runway 33', or the north-western 'end', known as 'Runway 15'. The decision over which runway to use was largely dependent upon wind speed and direction, but in STS-7's pre-flight press kit, Crippen was aiming for Runway 15. Sadly, not until February 1984 would a Shuttle crew make landfall in Florida, although Crippen, Hauck, Ride and Thagard would all make landings there later in their careers.

The resultant three-hour delay to STS-7's homecoming, therefore, gave the crew some much deserved free time and, said Rick Hauck, provided them with an opportunity to hold a makeshift, Earth-circling Olympics. "Someone said 'Okay, we'll time this'. Each person, in turn, had their hands coming up from middeck to flight deck through that opening on the port side, hands curled over the floor of the flight deck. On the count of three," Hauck explained, snapping his fingers, "we went as fast as we could up into the flight deck, down through the starboard entryway, down through the middeck and back up. We gave out five awards. Sally won the fastest woman. John Fabian won the competitor that caused the most injuries; no-one got hurt, but I think his leg hit Crip coming around at one point. I think Norm Thagard was the fastest man. Crip was the most injured!"

Eventually, after the hopes of an East Coast touchdown came to nothing, Crippen and Hauck duly fired Challenger's OMS engines at 12:56 pm to begin the hour-long glide to Earth. Sally Ride was pleased. "I remember being disappointed that we weren't going to land in Florida," she said later, "but I grew up in California and we'd spent a lot of time at Edwards Air Force Base. The pilots had done a lot of approach and landing practice at Edwards, so it almost felt like a second home. But there weren't many people there waiting for us!"

It was true. All of the astronauts' families were gathered at the viewing site at KSC. Nonetheless, Challenger's second touchdown in just over two months, occurring at 1:56:59 pm, was near perfect. Her systems had performed satisfactorily throughout re-entry and landing, but during towing operations a chattering noise was heard from one of the wheels on her right-hand main gear. The Shuttle had to be jacked up, the wheel removed, its brake assembly disassembled and the wheel remounted before towing could resume.

Detailed inspections revealed that the right-hand inboard brake had actually suffered major structural damage to two of its rotors, including the beryllium heat sink and carbon lining segments. Additionally, the right-hand outboard brake had two loose carbon pads with retainer washers missing. Cracked retaining washers were found in all brake assemblies and it was discovered that a similar situation might have occurred on previous Shuttle missions with no adverse effects. None, however, had been positively identified before STS-7.

It became clear that the washers had probably cracked during their manufacture or pre-fiight assembly, with structural and thermal analyses confirming that neither the flight nor landing could have caused the damage. One of the main 'to-do' tasks on the list for Challenger's processing team at KSC before her next mission, STS-8 in August 1983, would be the replacement of all cracked or suspect brake washers.

The NASA convoy responsible for recovering STS-7 after touchdown was somewhat smaller than intended, due to the diverted landing site: instead of the 24 vehicles and 110 personnel normally in attendance, only six trucks and 24 people were at Edwards on June 24th. As with previous flights, they determined that residual hazardous vapours were below significant levels and began attaching purging and coolant equipment to Challenger's aft fuselage. These measures enabled them to remove re-entry heat from the Shuttle and better protect its electronic hardware.

Half an hour after landing, Crippen, Hauck, Fabian, Ride and Thagard departed Challenger, using an airliner-like mobile stairway. Ground personnel then replaced the astronauts on the flight deck to complete safing activities and prepared the vehicle for transfer to the enormous Mate-Demate Device (MDD) hoisting crane, which would later install her atop the Boeing 747 and attach a tail cone to protect her main engines and OMS pods for the return flight to Florida.

When the astronauts returned to Houston, the media frenzy was more intense than previous missions, although their opportunities to relax were limited. Almost immediately, Crippen was immersed in training to lead the high-profile Solar Max repair - a mission to which he was assigned before STS-7 lifted off - while Thagard had joined the Spacelab-3 flight. Before 1983 was out, Fabian was attached to a new crew and Hauck received his first command. Ride, too, would fly again, teamed with Crippen once more. In fact, by the end of 1984, 'Crip' would acquire the new and perhaps more fitting nickname of 'Mr Shuttle'.

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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