Sunday, August 28, 2016

Fwd: 15 Years Since STS-105



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From: "Gary Johnson" <gjohnson144@comcast.net>
Date: August 28, 2016 at 9:12:05 AM CDT
To: "Gary Johnson" <gjohnson144@comcast.net>
Subject: FW: 15 Years Since STS-105

 

AmericaSpace

AmericaSpace

For a nation that explores
August 27th, 2016 

'To Train a Mission': 15 Years Since STS-105 (Part 1)

By Ben Evans

 

Fifteen years have now passed since STS-105 exchanged crews and supplies at the International Space Station (ISS). Photo Credit: NASA

Fifteen years have now passed since STS-105 exchanged crews and supplies at the International Space Station (ISS). Photo Credit: NASA

Fifteen years ago, this month, 10 astronauts and cosmonauts from the United States and Russia celebrated 1,000 days of orbital operations for the International Space Station (ISS). In August 2001, Shuttle Discovery's STS-105 astronauts—Commander Scott "Doc" Horowitz, Pilot Rick "C.J." Sturckow, and Mission Specialists Pat Forrester and Dan Barry—delivered the third resident crew to the fledgling outpost, supported a pair of critical EVAs, and returned to Earth with its outgoing second crew. Additionally, STS-105 transported over 7,000 pounds (4,000 kg) of equipment and supplies to the space station, aboard the Leonardo Multi-Purpose Logistics Module (MPLM).

Designated "Assembly Mission 7A.1," STS-105 was inserted into the manifest relatively late, to accommodate tasks after the arrival of the Quest airlock on shuttle flight STS-104, Assembly Mission 7A. In the words of Dan Barry, 7A.1 was a dot flight, "where we really are trying to respond to the things that the station needs to have." These "things" might include breakages or the appearance of specific issues and differed from "non-dot-flights"—7A or 8A, for instance—whose precise objectives and cargoes had been laid out several years before. "In some ways, it's more interesting … to make some of these late changes," said Barry. "It certainly is a challenge and we have trained for some things which, it turns out, we're not going to do. But I think that's part of business on being on space station and it's rewarding when you get out there and do the task on short notice."

Commander Scott "Doc" Horowitz (right) and Pilot Rick "C.J." Sturckow confer during a training session in April 2001. Photo Credit: NASA

Commander Scott "Doc" Horowitz (right) and Pilot Rick "C.J." Sturckow confer during a training session in April 2001. Photo Credit: NASA

Unusually, crew trained to perform their two EVAs from the shuttle's airlock, rather than from the newly-installed Quest. However, in the aftermath of Assembly Mission 6A in late April 2001—which installed "Canadarm2"—a series of subtle problems were detected with the station's 57.7-foot-long (17.6-meter) robotic manipulator. These problems arose in May 2001, following a communications error between Canadarm2's shoulder pitch joint and its main computer commanding unit.

Since the "Big Arm" was critically necessary to install Quest during shuttle flight STS-104 on Assembly Mission 7A, there existed a real possibility that STS-105 might end up flying first. "Right at a critical point in our training," said Forrester, "there were some real questions about whether or not [Assembly Mission 7A] and, specifically, getting Quest installed was going to happen or not. We had to make a decision that we needed to continue training in a way that we knew we would be able to duplicate it on flight. And so, early on, we started designing our EVAs around the shuttle airlock, to be able to cover the contingency that we went before 104, or, in this case, after 104."

As efforts to rectify Canadarm2's woes continued through late May and into early June, STS-104 was postponed until no sooner than early July. Fortunately, on 20 June, NASA announced that its launch with Quest would go ahead on 12 July, allowing STS-105 to be formally scheduled for early August. "It wasn't sure during training for STS-105 whether all the equipment necessary to install the airlock would be ready to support," Horowitz told a NASA interviewer, in the weeks before launch. "So in order for us to train a mission, we had to sort of divorce ourselves from the 104 flight and obvious way to do that was to train to do our EVAs out of our airlock on the space shuttle." By Horowitz's own admission, the decision "gave us a little bit of a hit" with regard to efficiency in terms of transferring the spacewalkers between the ISS and the shuttle. "But it gained us the ability to plan and train and execute a spacewalk," he added, "with a known configuration that, no matter when we flew, we would be able to support."

"Coming out of the shuttle airlock means that the hatches between the shuttle and the space station have to be closed," added Dan Barry. "And that kind of impact to our timeline we had to determine early on. If we waited until today, effectively, to determined that we did have [Quest] available, it's really too late to make the final planning changes to our flight plan and to our EVAs."

Pat Forrester (left) and Dan Barry use Virtual Reality (VR) tools to prepare for their two EVAs. Photo Credit: NASA

Pat Forrester (left) and Dan Barry use Virtual Reality (VR) tools to prepare for their two EVAs. Photo Credit: NASA

In addition to their EVAs, the STS-105 crew—named in December 2000 and originally targeted for launch in June 2001 (a tight, six-month training flow)—were tasked with exchanging two ISS increments. The Expedition 2 crew of Commander Yuri Usachev of Russia and his NASA flight engineers Jim Voss and Susan Helms would close out a multi-month stay about the station and be replaced by the Expedition 3 crew of Commander Frank Culbertson of NASA and his Russian flight engineers Vladimir Dezhurov and Mikhail Tyurin. "We haven't had a lot of training with Expedition 3, because they're so busy training for their increment," said Horowitz before the flight. "We have had several exercises together. We've done a couple of integrated simulations together, where they simulate that they're on the station or they're on the shuttle getting ready to go to the station. We've done some training together over in the mockups, where we practice emergency egress training that we will have to do as a crew. Other than that, though, they've spent a lot of time in Russia in training for their increment."

A further complication was that, for only the second time in the ISS assembly sequence, a dedicated shuttle crew would number only four members. Horowitz and Barry were joined by Sturckow and Forrester, with the remaining three seats aboard Discovery dedicated to the Expedition 3 crew for the uphill journey and to Expedition 2 for the return to Earth. This required the shuttle crew to adopt multiple tasks. For example, Horowitz assumed some RMS duties whilst the prime arm operator, Forrester, was outside on the mission's two spacewalks. "It's been a little bit of a training issue, because of all the time required to train to fly the arm, as well as do command duties," Horowitz admitted, "but everybody's pretty equally loaded. We've kind of spread the wealth around the crew to get everybody ready to do their tasks for this mission."

The mission faced potential delay in early August 2001, when the health of an injector stem in a Hydraulic Power Unit (HPU) on the left-hand Solid Rocket Booster (SRB) came into question. Engineers suspected that the injector might have sustained cracking, caused by age-related stress corrosion, probably a result of repeated water immersion as the booster splashed down in the Atlantic Ocean after each of its previous launches. The possibility of replacing the suspect unit might have delayed STS-105's launch by several days, but the Mission Management Team (MMT) concluded on 6 August that it was healthy and pressed ahead with countdown operations, tracking an opening launch attempt at 5:37 p.m. EDT on the 9th. However, high humidity and sea breezes threatened rain showers and a pall of ominous thunderclouds was observed off the end of the Shuttle Landing Facility (SLF) at the Cape. The latter would be needed in the unlikely event of a Return to Launch Site (RTLS) abort during ascent. At length, the launch attempt was called off at T-9 minutes.

After a 24-hour delay, due to poor weather at the Kennedy Space Center (KSC), Discovery roars to orbit on 10 August 2001. Photo Credit: NASA

After a 24-hour delay, due to poor weather at the Kennedy Space Center (KSC), Discovery roars to orbit on 10 August 2001. Photo Credit: NASA

This offered a period of discomfort for the crew. "Getting into your spacecraft is akin to going out in the drive in the morning to your car," Horowitz later joked, "except some joker overnight parked it on its rear bumper with the nose pointed in the air and you need about three people to push you up in the seat!" Next day, conditions had improved somewhat. "Tell the Expedition 2 guys to stand by," Horowitz told Launch Director Mike Leinbach. "We're on our way."

Weather conditions threatened to deteriorate on 10 August, causing mission managers to move T-0 a few minutes earlier to 5:10 p.m. EDT, right on the opening of that day's 10-minute "window." And without further ado, Discovery roared aloft, kicking off the 106th flight of the shuttle program. "A significant event in your life," was Horowitz's description of the shake, rattle and roll of what was his fourth launch into space. Two minutes and five seconds after liftoff, the twin SRBs were jettisoned and, said Horowitz, "then, there's a train-wreck," as a bright flash and a clang enveloped Discovery's cabin. The astronaut continued under the impulse of the three Space Shuttle Main Engines (SSMEs) for the next six minutes, until Main Engine Cutoff (MECO) and jettison of the External Tank (ET).

Shortly after orbital insertion, Sturckow noted that his Commander set to work devouring a pack of cheese tortellinis. "The rest of us weren't feeling up to that," the pilot wryly added, but this was nothing compared to the view of Discovery's middeck, where the upcoming Expedition 3 crew had already begun science-gathering, with the "Effects of Altered Gravity on Spinal Cord Excitability" experiment, known as "H-Reflex," which involved electrically stimulating the nerves in their legs as part of efforts to understand changes in locomotor function in weightlessness. "It looks like a lot of fun," Sturckow said later, with a measure of sarcasm, "but we didn't try it!"

As Horowitz and Sturckow oversaw the maneuvers, Barry and Forrester worked on the checkout of the Extravehicular Mobility Units (EMUs) for their two spacewalks. Early on the 12th, the shuttle had was about nine miles (15 km) from its quarry and had begun its final approach with the Terminal Initiation (TI) burn. Reaching 600 feet (180 meters), Horowitz assumed manual control of his ship and guided it through a quarter-circle to a point directly in "front" of the ISS, bearing toward the Pressurized Mating Adapter (PMA)-2 at the forward end of the U.S. Destiny lab. The maneuver was known as "TORVA"—a "Twice-Orbital-Rate +R-Bar to +V-Bar Approach"—which brought the shuttle from the Earth-radius-vector (R-bar) to a position along the station's velocity vector (V-bar) for docking.

Inside Discovery's cabin, the four STS-105 astronauts clustered together to bring the two spacecraft into a close mechanical embrace. As Horowitz floated near the aft flight deck controls, Sturckow oversaw a series of four "burns" from the Commander's seat and Forrester monitored the trajectory. Meanwhile, Barry was occupied with a hand-held laser to determine range and rate-of-approach numbers. "And then, finally at the end, I'll be looking out the window," Barry told a NASA interviewer, before launch, "telling Scott Horowitz what the final very close distances are, so that when we get within just a few inches, we know the right time to make the contacts that we need to make to get a successful docking."

Pausing at 30 feet (9 meters) to await a formal go-ahead from the Mission Control Centers (MCC) in Moscow and Houston, Texas, Horowitz then accomplished a smooth docking at 2:42 p.m. EDT. At the time of contact, the two spacecraft were about 240 miles (380 km) over northwestern Australia. "The connection is just the first part," said Barry. "We then have to pull the pieces together; we have to pull the space station together with the orbiter and make an airtight seal."

After two years of training for his expedition, Culbertson was eager to get on board the station. "C'mon, y'all, let's go!" he urged his crewmates. After concluding a ballet of pressure and leak checks, the hatches were opened at 4:41 p.m. and the incumbent Expedition 2 crew—Commander Yuri Usachev and Flight Engineers Jim Voss and Susan Helms, who had been aboard the complex since March—welcomed their new visitors.

By his own admission, Forrester had no idea what to expect on his first spaceflight. However, he was presented with what he described as "a real unique opportunity." In July 1993, when the U.S. Army sent him as an aerospace engineer to the Johnson Space Center (JSC) in Houston, Texas, Army astronaut Jim Voss was his first boss. "In fact, he was instrumental in bringing me down here," Forrester remembered. "I feel I owe a lot to him, just the fact that I was selected. If you had told me, eight years ago, that I would eventually be on the shuttle, going up to bring him back from his stay on the space station, I just couldn't have imagined it."

 

Copyright © 2016 AmericaSpace - All Rights Reserved

 


 

 

AmericaSpace

AmericaSpace

For a nation that explores
August 28th, 2016 

'Easier to Destroy Than Create': 15 Years Since STS-105 (Part 2)

By Ben Evans

 

STS-105 Mission Specialist Dan Barry translates along the U.S. Destiny lab during one of the flight's two EVAs. Photo Credit: NASA

STS-105 Mission Specialist Dan Barry translates along the U.S. Destiny lab during one of the flight's two EVAs. Photo Credit: NASA

Fifteen years have now passed since Shuttle Discovery dropped off and picked up crew members at the International Space Station (ISS) and supported a pair of Extravehicular Activities (EVAs) to transition the multi-national outpost toward a state of full utilization. By August 2001, the U.S. "core" of the station—its Destiny lab, its Unity node, its Canadarm2 robotic arm, its Quest airlock, and its first gigantic set of power-producing solar arrays—were in place, thereby wrapping up "Phase II" of the ISS Program and enabling the science-focused Phase III to begin. With the arrival of Expedition 3 Commander Frank Culbertson of NASA and his Russian flights engineers Vladimir Dezhurov and Mikhail Tyurin, science was to take center-stage, with the arrival of key research facilities aboard STS-105.

As outlined in yesterday's AmericaSpace history article, STS-105 was designated "Assembly Mission 7A.1," one of several dot flights, added to the ISS construction manifest to accommodate late plans and changes. After launching successfully on 10 August 2001, Commander Scott "Doc" Horowitz, Pilot Rick "C.J." Sturckow, and Mission Specialists Pat Forrester and Dan Barry oversaw two days of rendezvous and phasing maneuvers, which produced a successful docking about 46 hours into the flight. This was followed by pressurization and leak checks and the hatches were opened between Discovery and the space station. The outgoing Expedition 2 crew—Commander Yuri Usachev of Russia and NASA flight engineers Jim Voss and Susan Helms—were on hand to welcome the new arrivals aboard their orbital home.

"Hey, how you doing?" called Horowitz. "You ready for visitors?"

"Good to see you," replied Usachev.

The combined STS-105, Expedition 2 and Expedition 3 crews assemble in the Zvezda service module aboard the International Space Station (ISS) for a joint meal. Photo Credit: NASA

The combined STS-105, Expedition 2 and Expedition 3 crews assemble in the Zvezda service module aboard the International Space Station (ISS) for a joint meal. Photo Credit: NASA

After the bear-hugs and handshakes, one of the first joint tasks centered upon the Soyuz TM-32 spacecraft, where the outgoing and incoming expedition crews swapped out the seat liners of Usachev, Voss, and Helms and exchanged them with the seat liners of Dezhurov, Tyurin, and Culbertson. Leak checks were also performed on their Russian-made Sokol ("Falcon") space suits. This was to ensure the Soyuz and the suits could support a crew-return capability in the event of an emergency. In completing this step, Expedition 3 officially took control of the ISS, although it would be a few more days before a ceremonial handover of command would occur.

Although this was the second time that ISS crews had been changed via shuttle—following on the heels of the Expedition 1/2 swap on STS-102 in March 2001—Horowitz noted in his pre-flight interview that there were some differences. "One of the lessons we learned about crew exchange is you'd like to try to keep the crew exchange all at the same time, if you can," he said. "They [STS-102] had some other operational reasons they could not, because of the complexity of their mission and the different tasks that had to be done by different crew members on both sides. We've taken those lessons learned and tried to simplify their plan to make our exchange go smoother. One of the ways of doing that is to have the exchange all happen on one day, so that, if you have to do operations on either side of a closed hatch, you have the correct crew members on each side."

On the morning of 13 August, Forrester deftly unberthed the Leonardo Multi-Purpose Logistics Module (MPLM) from Discovery's payload bay, using the RMS. Aboard the ISS, the Expedition 2 crew activated the latching mechanisms at the Earth-facing (or "nadir") Common Berthing Mechanism (CBM) of the Unity node. Forrester "flew" the 9,000-pound (4,000-kg) Leonardo into position and, after receiving a Ready-to-Latch (RTL) indicator, it was attached to the station and a half-dozen fluid, power, and data connectors were connected. One of three MPLMs, Leonardo was making its second flight, having previously journeyed to the ISS in March 2001, and was securely in place at Unity nadir by 11:55 a.m. Over the next few hours, the RMS was detached from the module and the crews and Mission Control set to work pressurizing the vestibule between the Unity nadir CBM and Leonardo, ahead of hatch opening at 3:47 p.m.

Efforts then entered high gear to unload more than 7,000 pounds (3,200 kg) of equipment, food, clothing, and supplies. "Where the rubber meets the road" was the description offered by Dan Barry, who was responsible for the transfer to the station, as well as the loading of around 3,000 pounds (1,360 kg) of unneeded gear to bring back to Earth. Heading uphill were two new Expedite the Processing of Experiments for Space Station (EXPRESS) research racks—the 1,175-pound (533-kg) EXPRESS Rack-4 and the 1,199-pound (544-kg) EXPRESS Rack 5—for the Destiny lab. In organising the transfer, Barry picked up some advice from ISS "old hand" Voss, who suggested transferring everything over to the station, ensuring it was on "the right side of the hatch," before unpacking it. This prompted some praise from Yuri Usachev, who remarked that it was the fastest MPLM unloading he had seen. However, he cautioned: "Dan, it's easier to destroy than it is to create!"

An amused Susan Helms floats in front of supplies and equipment newly moved over from the Leonardo Multi-Purpose Logistics Module (MPLM). Photo Credit: NASA

An amused Susan Helms floats in front of supplies and equipment newly moved over from the Leonardo Multi-Purpose Logistics Module (MPLM). Photo Credit: NASA

As unloading operations progressed, Discovery herself conducted 240 thruster "burns" over the course of an hour on 14 August to slightly nudge the station's orbit a little higher. A second re-boost, which included 253 thruster firings, was performed on the 17th.

With their first EVA planned for the 16th, Barry and Forrester worked with Sturckow to checkout their suits and tools. The first spacewalk was tasked with installing the 1,000-pound (450-kg) Early Ammonia Servicer (EAS) onto the station's P-6 truss structure. The latter was designed to provide a spare ammonia supply for the early cooling system, should the need arise. "There are two completely separate coolant loops which are redundant, for the most part," said Barry, "but if there were to be a leak and it were to be severe enough to lose a significant amount of coolant, this device allows us to replenish that coolant."

Although the Quest airlock had been attached to the station and activated a few weeks earlier, neither EVA on STS-105 would use it. As a result, the hatches between Discovery and the rest of the station were closed on the afternoon of 15 August, in order that the pressure in the shuttle's cabin could be lowered from 14.7 psi to 10.2 psi to accommodate "pre-breathing" requirements. Next morning, at 9:58 a.m. EDT, on the 1,000th day since the first ISS hardware had launched to orbit in November 1998, Barry and Forrester headed out of the shuttle's airlock. Theirs was the 25th spacewalk devoted to ISS assembly and maintenance in just 32 months.

With only four "dedicated" crew members on the shuttle side, STS-105 saw Horowitz assume control of the RMS during the EVA. His first task was to grapple the EAS, whereupon Barry—designated "EV1," the lead spacewalker, with red stripes on the legs of his suit for identification—proceeded to tether himself to the mechanical arm. He was followed in short order by Forrester ("EV2," wearing a pure white suit) and the duo set to work removing six bolts to release the EAS from its Integrated Cargo Carrier (ICC) in Discovery's payload bay. When the payload was released, Horowitz gave it and the spacewalkers a ride on the RMS up to the P-6 truss. Upon reaching their destination, Barry set up an Articulating Portable Foot Restraint (APFR).

Since the limited reach of the 50-foot-long (15-meter) mechanical arm meant that it could not directly install the EAS, Horowitz instead released it into Barry's gloved hands. The sheer size of the EAS required Forrester to issue verbal directions on how to maneuver it into position. Next, the duo set to work tightening a bolt to hold the EAS in place and hooking up and securing a pair of cables for "keep-alive" electrical heaters. Completion of the EAS installation task put Barry and Forrester two-thirds of the way through their mandated tasks for EVA-1.

Dan Barry and Pat Forrester work to install the Early Ammonia Servicer (EAS) during EVA-1. The EAS can be clearly seen at the center of the image. Photo Credit: NASA

Dan Barry (left) and Pat Forrester work to install the Early Ammonia Servicer (EAS) during EVA-1. The EAS can be clearly seen at the center of the image. Photo Credit: NASA

As Horowitz handled RMS duties, Sturckow was the Intravehicular (IV) crew member, talking Barry and Forrester through each step and task and liaising with the Mission Control Center (MCC) to handle unforeseen problems and get-ahead tasks. In addition to installing the EAS, the duo also mounted the first pair of suitcase-sized Materials International Space Station Experiment (MISSE-1 and 2) packages onto handrails on the exterior of the Quest airlock, exposing hundreds of samples—including solar cell materials, optical coatings, and various composites—to the harsh atomic oxygen of low-Earth orbit. MISSE-1 and 2 were scheduled to be retrieved during shuttle mission STS-114 in March 2003, but the loss of Columbia postponed their returned to Earth for several years. Not until August 2005 did they finally reach terra firma.

Also on 17 August, following several days of "hand-over" briefings, Expedition 3 Commander Frank Culbertson ceremonially took control of the space station from his outgoing Expedition 2 counterpart, Yuri Usachev.

Barry and Forrester's second and final EVA got underway at 9:42 a.m. EDT on the 18th. They installed a pair of 45-foot-long (14-meter) heater cables along the port and starboard sides of the Destiny lab, setting the stage for the arrival of the S-0 hardware—the central component of the massive Integrated Truss Structure (ITS)—on Assembly Mission 8A in early 2002. Known as Launch-to-Activation (LTA) Cables, they were several inches thick and would provide backup power capability for the truss, if necessary. The S-0 hardware had to be deployed in a very short period of time and the risk of leaving its avionics boxes unpowered for too long carried the risk of damage. "Should 8A run into trouble during their spacewalk and be unable to get the truss completely installed, these cables provide an emergency source of power," Barry explained. "So they're really there just in case things don't go as planned during 8A's spacewalks."

"In order to tie those cables down, they have to be tied to handrails," added Horowitz, "and the handrails are not installed on the lab." When Destiny rose into orbit on Assembly Mission 5A in February 2001, clearances between the gigantic lab and the envelope of the shuttle's payload bay were so tight that it was not possible to install the handrails before launch. The only option was to install then on-orbit. This required Barry and Forrester to haul four bags—two laden with the LTA cables and two others with 11 handrails—out of Discovery's airlock and to the worksite. Once then, one man set himself up on the port side of Destiny and the other took up position on the starboard side, then unreeled the LTA cables like a pair of fire hoses and anchored them to the handrails. They hooked the cables to power receptacles on the lab. Altogether, the astronauts spent five hours and 29 minutes in vacuum. Upon their return to Discovery's airlock, Barry had accrued more than 25 hours of spacewalking time, across four excursions, with Forrester wrapping up the first pair of EVAs of his career.

Newly stocked and newly staffed, the International Space Station (ISS) disappears into the blackness as Discovery departs. Photo Credit: NASA

Newly stocked and newly staffed, the International Space Station (ISS) disappears into the blackness as Discovery departs. Photo Credit: NASA

It was turning into a busy first mission for Forrester. Next morning, backed up by Horowitz, he was at the controls of the RMS to detach Leonardo from the Unity nadir port and return it to Discovery's payload bay at 3:15 p.m. Between June 2002 and its final installation onto the ISS as the Permanent Multipurpose Module (PMM) in March 2011, Leonardo would fly a further six shuttle missions.

Bidding farewell to Culbertson, Dezhurov, and Tyurin, the STS-105 astronauts and departing Expedition 2 crew headed over to Discovery in the opening hours of 20 August, with hatch closure at 8 a.m. Undocking occurred at 10:52 a.m. and Sturckow took manual control, performing a strategic fly-around of the space station at a distance of 450 feet (140 meters), before withdrawing. It would not be his final flight to the ISS. In fact, at the time of writing, Sturckow is one of only four U.S. astronauts—joining Rick Mastracchio and the Kelly twins—to have visited the station as many as four times. The flyaround was not only a shuttle tradition, but was a fundamental necessity for upcoming crews, particularly through its photography component. "These photographs are very important for not only general publicity purposes, but we've actually used similar photographs," Sturckow said. "During our training, we'll pull out fly-around photos and see the exact configuration of different cables, for example."

Late in the mission, the STS-105 crew deployed the SimpleSat payload, designed to demonstrate inexpensive and commercially available hardware, including Global Positioning System (GPS) attitude control and pointing, in low-Earth orbit. The small satellite was ejected from a Getaway Special (GAS) canister at the rear end of Discovery's payload bay.

With landing at the Kennedy Space Center (KSC) Shuttle Landing Facility (SLF) planned for 22 August, the day prior was spent configuring the shuttle's systems and setting up incumbent seats in the middeck for Usachev, Voss, and Helms. These seats would help the trio, as they ended more than five months in weightlessness, to better withstand the forces of re-entry and a return to terrestrial gravity. "The reclined position," NASA noted, "has been proven to the most comfortable method of return to Earth from space by long-duration crew members."

Landing conditions in Florida were predicted to be excellent, obliging the Mission Management Team (MMT) to opt against activating the backup site at Edwards Air Force Base, Calif. The crew was awakened at 4:10 a.m. EDT on the 22nd and began stepping smartly through plans for a deorbit burn of the shuttle's Orbital Maneuvering System (OMS) engines at 11:37 a.m. This would produce the proper conditions to descend across southern Mexico, cross the Bay of Campeche, skirt the northwestern tip of the Yucatan peninsula, and head over the Gulf of Mexico, before entering Florida airspace and touching down at 12:46 p.m. Unfortunately, a rain shower popped up at the end of the SLF, leading to a one-orbit wave-off. Next time around, luck was on the crew's side. Horowitz and Sturckow executed the deorbit burn at 1:17 p.m. and Discovery alighted smoothly on the KSC runway at 2:23 p.m., wrapping up a spectacular 12-day mission.

 

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