Some Late Changes: Remembering Discovery’s Space Station Mission, 20 Years On

On this day in 2001, STS-105 and her crew—which included spacewalker Dan Barry, seen here—began an ambitious mission of science, spacewalking and supplies to the International Space Station (ISS). Photo Credit: NASA

Twenty years ago, astronauts and cosmonauts from the United States and Russia celebrated 1,000 days of orbital operations for the International Space Station (ISS). On 10 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 sessions of Extravehicular Activity (EVA) and returned to Earth with its outgoing second crew. Additionally, STS-105 transported 7,000 pounds (4,000 kg) of equipment and supplies to the space station aboard the Leonardo Multi-Purpose Logistics Module (MPLM)

Video Credit: National Space Society

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, during 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”—such as 7A or 8A—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.”

Dan Barry (right) and Pat Forrester work their Extravehicular Activity (EVA) tasks in the Virtual Reality (VR) simulator before the flight. 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 needed to install Quest during STS-104 on 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 [7A] and 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.”

Commander Scott “Doc” Horowitz practices his STS-105 duties before hte mis

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 fly in 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 said. “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.”

The STS-105 and Expedition 3 crews await a training session in the shuttle mission simulator. From right to left are Commander Scott “Doc” Horowitz, Pilot Rick “C.J.” Sturckow, Mission Specialists Dan Barry and Pat Forrester and Expedition 3 Commander Frank Culbertson and Flight Engineers Vladimir Dezhurov and Mikhail Tyurin. Photo Credit: NASA

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 Barry. “And that kind of impact to our timeline we had to determine early on. If we waited until today, effectively, to determine 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.”

The “core” STS-105 shuttle crew, here pictured at the flight line at Ellington Field, were assigned only a few months before launch. From left to right are Dan Barry, Scott “Doc” Horowitz, Rick “C.J.” Sturckow and Pat Forrester. 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 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 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.” 

Expedition 3 Commander Frank Culbertson is pictured in his shuttle Launch and Entry Suit (LES) during pre-flight training. Photo Credit: NASA

STS-105 faced potential delay in early August 2001, when the health of an injector stem in a Hydraulic Power Unit (HPU) on the shuttle’s 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.

Video Credit: NASA/Andy Meyrow/YouTube

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 was scrubbed at T-9 minutes.

This offered some discomfort for the crew. “Getting into your spacecraft is akin to going out in the drive in the morning to your car,” Horowitz quipped, “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. “Tell the Expedition 2 guys to stand by,” Horowitz told Launch Director Mike Leinbach. “We’re on our way.”

Discovery begins her 30th mission on 10 August 2001. Photo Credit: NASA

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”. “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). 

Discovery roars into orbit on 10 August 2001, two decades ago today. Photo Credit: NASA

Shortly after orbital insertion, Sturckow noted that Horowitz 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 to understand changes in motor function in weightlessness. “It looks like a lot of fun,” Sturckow said sarcastically, “but we didn’t try it!”

As Horowitz and Sturckow oversaw the maneuvers to reach the ISS, Barry and Forrester checked out their space suits for the two spacewalks. Early on the 12th, Horowitz assumed manual control of his ship and guided it through a quarter-circle to a point directly in “front” of the station, bearing towards the Pressurized Mating Adapter (PMA)-2 at the forward end of the U.S. Destiny lab.

Presumably sometime after wolfing down a snack of cheese tortellinis, STS-105 Commander Scott “Doc” Horowitz consults flight notes early on Flight Day One. Photo Credit: NASA

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.

Pausing at 30 feet (9 meters) to await a formal go-ahead from the Mission Control Centers (MCC) in Moscow and Houston, Texas, Horowitz 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.

Impressive view of Discovery’s payload bay, revealing the docking mechanism of the Orbiter Docking System (ODS) in the foreground and the Leonardo Multi-Purpose Logistics Module (MPLM) at the rear. Photo Credit: NASA

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. Hatches swung open at 4:41 p.m. and the incumbent Expedition 2 crew welcomed their new visitors.

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

“Good to see you,” replied Usachev.

Docking latches on the shuttle side (lower) and ISS side (upper) prepare to engage as STS-105 Commander Scott “Doc” Horowitz completes the rendezvous and docking procedure. 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 seat liners of Dezhurov, Tyurin and Culbertson. Leak checks were also performed on their Russian-made Sokol (“Falcon”) space suits. This was in order to ensure that the Soyuz and the suits were ready for a sudden emergency evacuation.

Although this was the second time that ISS crews had been changed via shuttle—after the Expedition 1/2 swap on STS-102 in March 2001—Horowitz noted some differences.

Horowitz and Culbertson prepare to open the hatches between Discovery and the space station. Photo Credit: NASA

“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,” he said. “[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.” 

“Easier to destroy than create” were words of advice offered by Expedition 2 Commander Yuri Usachev (left) to STS-105 Mission Specialist Dan Barry (second from left). Photo Credit: NASA

On the morning of 13 August, Forrester deftly unberthed the Leonardo Multi-Purpose Logistics Module (MPLM) from Discovery’s payload bay, using the RMS. He then “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.

Dan Barry’s face is visible as he floats high above Discovery’s payload bay. Photo Credit: NASA

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 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 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 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!”

Dan Barry (left) and Pat Forrester (back to camera) work with the Early Ammonia Servicer (EAS) during its installation. Photo Credit: NASA

The first spacewalk was tasked with installing the Early Ammonia Servicer (EAS) onto the station’s P-6 truss structure. This would furnish a spare ammonia supply for the station’s early cooling system, should the need arise. 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, 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. With only four “dedicated” crewmen 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”—tethered himself to the mechanical arm.

Dan Barry (just visible below center) and Pat Forrester (top) manhandle the Early Ammonia Servicer (EAS) into place. Photo Credit: NASA

He was followed in short order by Forrester (“EV2”) 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.

Dan Barry stabilizes himself with a handrail during one of his EVAs with Pat Forrester. Photo Credit: NASA

As Horowitz handled RMS duties, Sturckow was the Intravehicular (IV) crew member, talking Barry and Forrester through each step. In addition to 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.

Incoming Expedition 3 Commander Frank Culbertson (right) shakes hands with outgoing Expedition 2 Commander Yuri Usachev. Photo Credit: NASA

Also on 17 August, following several days of “hand-over” briefings, Culbertson ceremonially took control of the space station from Usachev.

Barry and Forrester’s second and final EVA got underway on the 18th. They installed a pair of 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.

Pat Forrester is pictured during one of his two sessions of Extravehicular Activity (EVA) with Dan Barry. Photo Credit: NASA

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.”

When Destiny rose into orbit on Assembly Mission 5A in February 2001, clearances between the lab and 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 with handrails—out of Discovery’s airlock and to the worksite.

The three crews of STS-105, Expedition 2 and Expedition 3 share a joint meal inside Russia’s Zvezda service module. Photo Credit: NASA

Once there, 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.

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.

Jim Voss (left) and Yuri Usachev strap Susan Helms into her recumbent seat on Discovery’s middeck, ahead of their return to Earth. Photo Credit: NASA

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.

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.”

Flight controllers in the Mission Control Center (MCC) at the Johnson Space Center (JSC) in Houston, Texas, watch as Discovery lands safely on 22 August 2001. Photo Credit: NASA

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 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.

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 and Discovery alighted smoothly on the KSC runway at 2:23 p.m., wrapping up a successful 12-day mission.

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