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Space Shuttle Orbiter Engineering
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0:00
For the past 9 minutes the Space Shuttle has been powering its way through the atmosphere. Propelled forward by 2 massive solid rocket boosters, completing their duties 2 minutes into the flight, they are now falling back to earth where they will be refurbished and reused. The final push comes from the orbiter's 3 main engines, being fed liquid oxygen and liquid hydrogen from the colossal orange external tank at an astonishing rate.
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Having drained the 700 tonnes of fuel and oxidiser from its tanks the time has come to shut down the powerful main engines and jettison the external tank. The astronauts inside the orbiter will find themselves transitioning from a exilerating thundering journey to a serene silent cruise, becoming weightless the moment the engines power down. The light of the shining blue earth below them flood through the windows of the crew cabin.
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The journey to orbit has ended, but their mission has just begun. The space shuttle was not just a rocket, it was a mobile laboratory, a home in space, and it came with all the tools the astronauts needed to not just survive , but to complete complicated tasks in space. A sanctuary amidst the unforgiving expanse of space, the orbiter provided a secure haven, sustaining a breathable atmosphere, facilitating precise maneuvers, a payload bay capable of
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carrying massive spacecraft like the Hubble Space Telescope, and the machinery needed to repair them when needed. This is the insane engineering of the Space Shuttle Orbiter The astronauts' jobs begin the moment they reach orbit. The orbiter has released the external tank and it’s beginning its journey back through the atmosphere where it will disintegrate. This is the last view anyone will have of the external tank intact, and it was vital
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that photos were taken of it to check for any issues that could have occurred on ascent. To do this the commander of the orbiter needs to pitch the shuttle onto its back using its maneuvering system. Scattered all over the orbiter are smaller rocket nozzles, part of the reaction control system. This removable module in the nose of the aircraft was the forward reaction control system. [Footage]Inside there are two spherical tanks, an oxidiser tank filled with nitrogen tetroxide
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and a fuel tank filled with monomethyl hydrazine. This fuel oxidiser combination is unique. It doesn’t need an ignition source. It’s hypergolic. Meaning they spontaneously ignite upon contact with each other. But, both substances were extremely toxic. Producing ominous orange clouds of toxic gas. Breathing this in would cause your lungs to rapidly fill with fluid, and once in your bloodstream it interferes with the blood's ability to carry oxygen.
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Anyone working with the propellants had to wear pressurized breathing suits to prevent any chance of contact. The astronauts also had exclusion zones around these nozzles on space walks to prevent any danger of the chemicals coming back aboard. It’s an undesirable fuel to work with in many ways, but its advantages were why it was used. These hypergolic fuels were extremely reliable, igniting on contact with each other removed any need for complicated ignition systems that could fail.
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[REF] They could be stored for longer periods than cryogenic fuels that would have to be continually vented as temperatures rose, which makes cryogenic fuels unsuitable for longer missions like the space shuttle, with the longest space shuttle mission lasting 18 days this was critical. [FOOTAGE] The propellants could also be quickly mixed in precise volumes to provide precise and instantaneous thrust control. This was important when maneuvering in close proximity to another spacecraft.
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The propellants are fed into the combustion chamber through pressurization of the tanks with high pressure helium. Held in spherical kevlar composite tanks with titanium inner liners, an extremely lightweight tank, just 10 kilograms in weight, but nearly a half meter in diameter. Spherical tanks are the most weight efficient form of pressure vessel, with the highest volume to weight ratio. Ideally all rockets could use spherical tanks, but ultimately diameters increase too much
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as volume requirements rise and it’s preferable to minimize the cross-sectional area of the rocket to reduce drag. There is no turbopump needed here; the back pressure from the high pressure helium provides enough flow rate for the purposes of these low power rocket motors. In the forward reaction control system pod there are 12 main thrusters and there are 12 in each of the left and right rear pods too. For a total of 38 main thrusters, each capable of providing 3870 newtons of thrust with a
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specific impulse of 289 seconds. Sometimes even finer control was needed for delicate docking procedures and for this the orbiter had 6 smaller vernier thrusters capable of producing as little as 111 newtons. The same amount of force you would need to lift an 11 kilogram weight here on earth. With a total of 44 reaction control thrusters scattered around the orbiter the astronauts needed a way to control them.
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The controls were located at the commander's seat on the left side of the cockpit and here on the left side of the aft flight deck. The rear position was added to allow the commander to look out this rear window while maneuvering for rendezvous with other spacecraft or releasing payloads. Each station had a square-knobbed controller used for translational movements, in and out, side to side and up and down. And a more traditional flight stick, which was used to control attitude, pitch, roll
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and yaw. [[REF] There was also a flight computer where desired attitude and velocity changes could be entered with a keypad. Of course this was all fly by wire the commanders inputs were all fed into a computer which interpreted the commands and decided the best course of action. There was only one notable exception to this fly by wire system. ] I mean, there is nothing mechanically linked to any of the control surfaces or anything.
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Everything goes through the computer, everything you touch goes through the computer and the computer generates everything. We are concerned about things called single event upset, and you've probably heard of this before, where a cosmic ray comes in and upsets the computers and you can recover from anything. But because there was no way to raise the landing gear, we were concerned a single event upset if there was an automatic computer way to lower the wheels that you could get your
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wheels lowered on orbit and not be able to come home. So we always made that mechanical. And so once we got down to under 300 feet, 200 feet, that was the pilot's main job was to lower the wheels manually. Putting them back in place required ground crew to push them back in. So, because ionizing radiation in space could potentially trigger the computers to lower the landing gear, and with no way of raising them back up, they were lowered manually.
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The landing gears were held in place by a hooked lock that was released after the pilot flipped the protective covers of these two buttons, an arming button and button labeled “dn” for down. When this happened a hydraulic actuator released the hook holding the landing gears in place and allowed them to lower. The first day of the mission is now starting. [REF] The astronauts begin their tasks. The pilot and commander seated in the left and right seats in front of the instrument
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panel are busy working towards the first rendezvous with intelsat. Through the forward windows the astronauts can glimpse a distant bright dot, the satellite that they are maneuvering towards. These weren’t the only windows on board, there were additional overhead windows, along with rear windows looking into the payload bay, which for now remains closed. These windows were key to the reusability of the shuttle.
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The windows had to be durable enough to survive space debris impacts and capable of resisting the temperatures of re-entry The Space Shuttle's window structure had multiple layers of glass, each tailored to withstand different conditions. The pressure pane was engineered to endure the cabin pressure in space; it was made from 15.7 millimeters thick aluminosilicate glass that was tempered to be mechanically strong.
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On the outer edge of this pane, a red film was added to reflect back the heat into the vehicle to not be lost to space, while still letting visible light through. The outermost pane, or the thermal pane, was also 15.7 millimeters thick and capable of resisting temperatures up to 482 degrees celsius. There was also a large space between these two panes, which minimized heat transfer between the outer shell and the inner crew cabin.
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On one discovery mission one of these windows was struck by space debris, leaving a small crater in the window, but it did not break. [Footage] If it had, the astronauts inside were in no danger, as there was a center redundant pane, serving as a failsafe for both the thermal and pressure panes. It was 33 millimeters thick and made out of fused silica glass the same material that laboratory crucibles and beakers are made of.
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The rear windows looking into the payload area did not have the outer thermal pane since they would not be exposed to the extreme super heated plasma during re-entry. There were no windows in the middeck, below the crew deck. The middeck is where many of the science experiments in orbit were performed, and this is where the astronauts slept and ate. There were stations where the astronauts could strap themselves to the walls in the weightless environment, but not everyone chose to use them.
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The commander and pilot generally slept up on the flight deck that they would just loosely strap themselves in their commander in pilot seats because that was a good way, and you want to be kind of strapped in. There were some astronauts like story Musgrave that liked to free float around in space, but he would bump into people, and I heard that it was quite annoying sometimes. But the rest of us, you'd have a cloth sleeping bag that's made out of just light material
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like this where you velcro it to a bulkhead or the ceiling and you just zip yourself up in it. The time has now come to open the payload doors. The doors needed to open shortly after reaching orbit as one of the space shuttles vital life support systems required them to be open. The temperature control system. Two radiator panels are attached to each of the forward payload bay doors. Freon filled tubes snake around these panels.
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Where they radiate heat absorbed from a heat exchanger located inside the orbiter into space. The payload doors themselves are made from a graphite/epoxy composite material which reduced the weight of the doors by 408 kilograms over a comparable aluminium design. At the time this was the largest aerospace composite structure ever made. [Page 173] Covering the payload bay which was 18.3 meters long and 4.6 meters wide.
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The largest and heaviest payload it ever carried was on STS-93 with the Chandra X-Ray Observatory coming in at 22.7 tonnes. Maxing out the shuttle's capacity. This mission came worryingly close to disaster. During each refurbishment of the shuttles main engines, they were inspected with ultrasound [REF] to find signs of damage. In some cases damage may be detected in one of the liquid oxygen posts that delivered
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liquid oxygen to the combustion chamber, and instead of replacing the entire expensive and difficult to manufacture injection assembly, the post was simply deactivated with a gold pin that plugged the channel. During the pre-launch start up sequence of the main shuttle engines on STS-93 one of these gold pins was ejected out and struck the hydrogen coolant channels in the nozzle, resulting in a hydrogen leak that you can actually see here in images of the launch.
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The engine detected a decrease in combustion chamber pressure, and opened the oxidiser valve to increase thrust, the engine had no way of knowing the issue was a hydrogen leak. It could only detect the drop in combustion chamber pressure and respond by making the combustion less fuel rich, which increases thrust and temperature. This incident resulted in a maintenance policy switch that meant damaged oxygen posts had to be replaced and not simply plugged.
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Thankfully the engine survived and the mission was successfully completed despite the main engines shutting down prematurely as a result of the oxygen depletion sensors being triggered. So the orbiter was 4.6 m/s off it’s target orbital velocity. Thankfully the Orbiter has an orbital maneuvering system that could bring it up to its desired velocity These large rocket nozzles were not part of the reaction control system, and were capable of providing 305 meters per second of additional velocity.
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Powered by the same hypergolic fuel and oxidiser as the RCS system, from tanks hidden within the OMS pods, capable of holding 4 tonnes of fuel and 6.7 tonnes of oxidiser. When performing large orbital changes like this it was important for the Space Shuttle to know precisely where it was, and to do this it could open these doors on the left side of the orbiter's nose, revealing the star tracker optics. These star trackers analyzed positions of the stars in the sky to determine exactly
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where the orbiter was, allowing it to precisely navigate in orbit. Once the space shuttle has arrived at its target orbit, the real work can begin. On Bruce’s mission, STS 49, the first task was to rendezvous with that stranded communications satellite. Carefully maneuvering the orbiter closer to the satellite as the satellite's operators attempted to stabilize its spin. As they approached 2 astronauts. Pierre Thout and Richard Hieb donned their EVA suits in the middeck and prepared to enter
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the airlock. The airlock for this mission was located inside the crew cabin of the middeck,but it could be configured to be outside in the payload area. During the construction of the international space station, a special docking system was also installed, which was required to allow the space shuttle to dock to both Russian and American spacecraft. It was called the androgynous peripheral attach system. The androgynous name comes from the fact that both the target and the receiving end look
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identical, with no male or female parts, with the goal of this being a universal docking system allowing any two spacecraft to dock together. As Goddard intended. Each side had a ring with three petals equally distributed. One side extended its mating ring for a soft capture, where the 3 petals of each side come together and connect with these latches. [REF] At this point, the soft capture ring is retracted and 12 latches engage to form an airtight connection between the two spacecraft.
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This system was used extensively during the construction of the international space station, which the space shuttle had an instrumental role in transporting and assembling in space. Including the very first modules to be connected in 1998 on STS 88, when the orbiter docked with the Russian Zarya module using this docking ring, and proceeded to connect the unity module. On STS-49, Bruce’s mission, the stranded satellite was never intended to be docked
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with and had no docking points, and thus to capture the stranded satellite the astronauts needed to perform an EVA and manually grab the satellite using a capture bar specifically designed for this mission, but not everything went to plan So we made several attempts to grab this satellite with the capture bar, but every time Pierre touched the bottom of the satellite with the capture bar, it bounced off out of control.
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Fortunately, the engineers that owned Intel sat, they could send commands back up to it, restabilize it so we could maneuver back closer to it and try again. So we tried three or four times the first day to grab it every time it bounced off. Second day we tried again every time it bounced off. So at that point we were kind of at a loss. We didn't know what we were going to do. And of course, all this time, I'm operating the arm. I'm chasing the satellite with Pierre on the end of it.
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And so it was a very demanding part of the flight. So two days of trying the ground said, okay, we're going to take the third day off, and then we're go back out and try on the fourth day to do it again. Well, of course we felt like the mission was lost. So the ground told us, go ahead, get a good night's sleep, we'll call you in the morning. So we got to thinking, and matter of fact, I saw that I could hear that Dan and Chile
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were talking up on the flight deck when we were supposed to be asleep. So I floated up to the flight deck with them and they were talking about how Endeavor was so maneuverable and was so efficient on its fuel burn that they thought we could get close enough to the satellite to where Rick and Pierre could just grab it with their gloved hands. And we saw it at one point when Pierre got the capture bar, one side of the capture bar fired, and it almost immediately stopped the rotation.
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So we knew that it was going to be easy to stop the rotation if Rick and Pierre could just grab the bottom of the satellite. The problem was is now what do you do if you do grab the satellite? You've got two guys out there holding a 9,000 pound satellite with no way to get it back on the rocket motor that we took up to strap to it to send it back up to the proper orbit. Well, I scratched my head while I was up there and I knew that because after we finished
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this satellite business, two other astronauts, Tom Akers and Kathy Thornton, they were going to go out and do some practice of assembly of the Space station. We hadn't built the space station at that point, and they were going to be out trying to do some methods for that. Well, in order to accommodate all the different sized astronauts, the EVA suits or the spacewalking suits, they're made out of different components, different length arms, different size torsos, those sorts of things.
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And Rick Hebe is this big, Kathy Thornton was this tall, and then Tom and Pierre are about my size. So in order to accommodate four astronauts on two different spacewalks of those different sizes, we for the first time ever had three full EVA suit, the components of three full EVA suits on board. So I got to thinking, I said, well, we have three suits on board. Why don't we send three space walkers out? We can have two people grab it and then one person put the capture bar on because the
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capture bar had to be attached to the satellite because that was what was going to attach it to the rocket motor that we brought up. However, this plan had one problem. The airlock was only designed for two people. The airlock consisted of two air tight doors. Once inside, with the doors sealed, the astronauts could depressurize the inside by venting the air to space. This could only be done from inside the hatch, but repressurization could be done from outside and inside.
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For obvious safety reasons. This process took about 30 minutes and while it happened the astronauts were connected to life support umbilicals so they didn't have to waste their internal supplies during the wait. This was the first problem. There were only 2 life support umbilicals available. It was also going to be a tight squeeze for three astronauts with full EVA gear on, as the cylindrical airlock inside the mid-deck was just 160 centimeters in diameter and 210 centimeters high.
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The third astronaut was going to need to make some sacrifices. So unlike normally where you just have two astronauts, you put 'em in the airlock, you close the door with Tom, he had to go on all of his internal controls and we float him in the airlock upside down. So now you've got Rick and Pierre right side up, and Tom Akers head down in the airlock, and he's on his internal systems now where Rick and Pierre are still attached to the
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umbilicals inside, close the airlock evacuate it, and then all three of them floated out. And here, the three astronauts got to work. With Bruce on the remote manipulator arm controls inside the orbiter, and he was chosen for a very specific reason. He was a coast guard helicopter pilot. And the reason Dan wanted to have a Coast Guard helicopter pilot on the arm, and the reason for that is, is that operating the arm, the controls that you use are vaguely
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similar to operating a helicopter because in a helicopter you have to fly with both hands and both feet. Well, when you're operating the arm, you've got two controllers, you've got a rotational hand controller and a translational hand controller. So the translational hand controller, you move up, down, sideways, in and out. Rotational hand controller controls the attitude of the arm. So it's very much flying a helicopter and you can't be thinking about it when you're in a very tight situation.
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You've got to be the arm. The canadarm, named after its country of origin, was a multifunctional tool used for many tasks aboard the shuttle. A simple articulated arm may not seem overly impressive, but the unique physics of a weightless environment and desire to minimize the launch weight of the space shuttle made for a very interesting engineering challenge. The entire 15 meter long arm weighs just 430 kilograms, and despite being able to move
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30 tonnes in orbit, it couldn’t even hold up its own weight on earth. [REF] The booms were made from low weight epoxy graphite composite, with 6 joints. 2 joints at its shoulder for yaw and pitch, 1 elbow pitch joint, and 3 joints at the wrist for yaw, pitch and roll. For a total of 6 degrees of freedom of movement, exactly like your own arm. However your elbow joint is only capable of about 140 degrees of pitch before your biceps get in the way.
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The Canadarms elbow joint rotational axis is offset by 0.15 meters to allow up to 160 degrees of rotation. [REF] Because the arm is working in a weightless environment motors don’t need to be able to apply that much torque. Each motor could produce 0.7 newton meters of torque. With no friction in space a small force can move any mass, it just depends how long you want it to take. In the same way an ion thruster with thrusts of just 25 millinewtons could theoretically
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get a spacecraft up to lightspeed if it had enough propellant. However, the dangers of inertia are still real. If a satellite was moving quickly relative to the arm it could easily bend and break the arm. So slow delicate movement is the name of the game and the motor can work in reverse to assist each joint's brake system. The loaded arm speed had a maximum speed of just 6 centimeters per second. The arm had a unique end fixture designed to grapple onto attachment points on satellites.
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However, because the intelsat was never intended to be rendezvoused with, it didn't have any grapple points installed. So the capture bar had an attachment point for the second stage rocket and had a grapple point allowing the canadarm to grab hold of it once it was securely attached. The grapple point is a simple metallic pin with three lobes at its base. [REF] This is all the arm needed to firmly grab onto the intelsat.
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The end effector of the canadarm used a naturally self centering wire grapple system to hold onto this pin. Three wires, each anchored at two points. One point is stationary, while the secondary anchor point is attached to a rotating ring. [REF] Once Bruce had maneuvered the arm over the grapple rod using the camera feed this rotating ring would turn and ensnare the pin, pulling it to the center. The pin is then pulled inwards until the three lobes at its base lock into corresponding
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cut outs on the outside grabble ring. A simple, but effective mechanism. With the satellite now secure the three astronauts could get to work attaching the new second stage to the capture bar, which they did successfully, allowing intelsat to raise itself to geostationary orbit where it operated for 21 years. STS 49 had another mission to complete. A test run of space shuttle building techniques, but with their time in orbit running out. That mission lost a day.
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Life support systems onboard were supplied with enough gasses for the planned duration of the mission. Spherical tanks in the mid fuselage contained high pressure oxygen and nitrogen. With 3 nitrogen tanks and 1 oxygen. Used to create a breathable atmosphere of 80% nitrogen and 20% oxygen. Of course carbon dioxide needed to be scrubbed from the air, and this was done by passing the cabin air through lithium hydroxide canisters located underneath the middeck.
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These solid canisters would react with the CO2 to remove it from the atmosphere and create water in the process. This was not a renewable solution so every 12 hours the crew would access and replace these canisters through this hatch on the middeck bay. There were also oxygen and hydrogen tanks used for the space shuttles power system. A fuel cell that reacted the hydrogen and oxygen to produce water and electricity. These powered everything on board, and produced water in the process.
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But this water carried some extra hydrogen gas, so before the water could be used it had to go through a process of degassing, which separates the hydrogen and dumps it overboard. It was now time to prepare for re-entry and the first step was closing those payload doors, but on STS 49 another problem was encountered. The payload doors would not latch due to thermal warping of the doors, requiring some creative problem solving.
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Well, there's always two astronauts trained to do EVAs and I was trained to do an EVA on my first flight, and that's for a contingency. If for example, the payload bay doors wouldn't close or latch all the way when you're on orbit, we have special tools where we could winch 'em closed and latch 'em all together. And matter of fact, on STS 49 after we had trouble getting the satellite to launch because of a different switch configuration, we got up there and the payload bay doors wouldn't
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close all the way. And so we thought, oh man, do we need to go back out and do that? So your first attempt to fix something like that is the thermal loads on the space shuttle. As you can imagine, you're 200 degrees on the sunny side and 200 degrees below zero on the dark side. So a lot of times you'll get a little bit of an oil canning effect or a little twisting of the fuselage just because of the thermal effects. And that's what we did.
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We went ahead into what we call the barbecue mode and we started, so we went ahead and orbited the earth and the barbecue mode to try to equalize the temperatures on the shuttle when we couldn't get the payload bay doors to close all the way. And When you say barbecue mode, do you mean like a spit roast? It's rotating, Yes. Yeah, it's not that fast, but you do that to where you try to equally heat while you're going through the sun and through the dark.
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And I think it was just one or, but we had to do, and we tried to close the doors again and they latched. With the doors successfully closed, the space shuttle can begin its preparations to re-enter the earth's atmosphere. Firing the OMS engines once more to slow the orbital velocity and slowly bring it back into earth’s atmosphere. At the moment of reentry, the space shuttle will be traveling between 7 and 8 km/s. Entering the thin upper atmosphere at 30 times the speed of sound.
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A speed so great that it begins to rip air molecules apart, creating a glowing cloud of charged plasma around the lower surface of the orbiter. With peak temperatures reaching 1650 degree celsius (3000 F). To not only withstand this immense heat, but to transition to a glider capable of landing on a runway required some incredible innovative engineering. Combining aerospace and aviation technologies like never before. A true space plane.
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Episode 3 of the insane engineering of the space shuttle, detailing the engineering of re-entry and landing will be uploaded in the coming weeks as we take a short break to celebrate the holidays with our friends and family. You are likely doing the same and perhaps you are looking for a thoughtful gift for the enthusiastic learners in your life, or perhaps you want to set some new years goals and learn some valuable skills Brilliant can help you with both.
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