A quick navigational tip: Forward is the front, Aft is the back.
The space shuttle, seen here, is the name given to the whole system. The space shuttle system consists of 3 parts. The first, and obviously main part, is the orbiter, the white, delta winged space plane. The second part is the external tank, the big orange tank in which the orbiter is latched onto. The third part is actually 2 parts, the solid rocket boosters, the 2 white 'sticks' latched onto each side of the orange external tank. Easily identifiable in that picture, right? Good.
The Solid Rocket Boosters
The function of the solid rocket boosters is to assist the other two pieces, the orbiter with the external tank, into orbit. It's called Solid Rocket Boosters, or SRBs, because the gasoline used inside them is not liquid, but solid. If you want an easy example, grab a match and strike it. That 1 second flare it does before settling and burning out is done thanks to the tip of the match, which is a typical type of a solid fuel, or propellant. Now imagine that, blown up a million times bigger (I'm exaggerating, but you get the idea). And imagine not just the tip, but ALL of the stick, is solid propellant, sealed inside a cylinder. BOOM. It's funny. I can imagine one day, decades ago, NASA was striking matches and they said, "why don't we build a BIG match and use that as a rocket?" Fast forward to April 12, 1981, where two of those "big matches" helped launch the very first space shuttle flight into orbit. Today, they're still used.One problem about the boosters is that once ignited, they can't be turned off until they burn out 2 minutes later after ignition. That means that when the countdown hits 0 and the boosters are ignited, the entire shuttle is commited to liftoff, and there can't be any cutoffs until the SRBs burn out. Remember this. Once they burn out, they separate from the external tank and fall into the ocean, using parachutes stored in its nose to reduce its fall, where two recovery ships, the Liberty Star and the Freedom Star, are waiting to drag them back to land for refurbishing for a later flight.
The External Tank: Big gas tank... or is it liquid gas?
The function of the external tank, besides being the backbone of the entire system (the orbiter and boosters are latched onto the tank), is to store the liquid propellant for the orbiter's 3 main engines. Since the orbiter was designed to carry cargo to and from space, it didn't have space for a tank for its main engines. Therefore, the external tank was created. It fuels the main engines on its 8 and a half minute climb to orbit, the first 2 minutes being assisted by the SRBs.
The tank consists of 3 halves. The upper half houses the liquid oxygen tank, where liquid oxygen (also called LOX... because they can.) is kept at -297 degrees farenheit. Think about it, the very air you breathe, chilled to the point where it becomes liquid. The lower half houses the liquid hydrogen tank,, where, of course, liquid hydrogen is stored at−423 degrees farenheit. The middle, called the intertank, contains all the controls for the tank. Because of the temperature of the liquids, the tank os covered in insulating foam, to preserve temperature on the inside, and prevent ice buildup on the outside.
The orbiter: The main part of the shuttle system
The orbiter, depicted here flying around 225 miles above the Earth (picture taken from the International Space Station), is the main part of the shuttle system. This is the vehicle that reaches orbit, with cargo and crew, executes in-orbit operations, and safely returns crew and cargo back to Earth in an unpowered glider configuration.
The shuttle has 4 means of getting around. The first is the three space shuttle main engines (SSMEs), used only in the 8 and a half minute climb to orbit. Above the left and right engine are two smaller engine nozzles, called the Orbital Maneuvering System engines (OMS engines), which are used in orbit to raise the shuttle's speed, and therefore, orbit height, decrease it, decrease it to a point where the lowest point in the orbit causes entry in the atmosphere (that event is called a Deorbit burn), and make course corrections, if the mission calls for it (example, for catching up to the ISS - International Space Station). The OMS engines are sometimes used immediately after SRB separation during ascent to provide an assist boost for the main engines. Third are the RCS (reactant control system) jets, only usable in orbit, several located in the front, and several in the back. They are used to control the shuttle's attitude (position) , move around slowly, and make precise speed corrections, usually for approaching an object in space, be it a satellite or the ISS. During re-entry, the forward (front) RCS jets are turned off, and only the aft (back) jets are used for the maneuvers necessary to bleed off speed. These are later slowly deactivated as the air thickens around the shuttle, in which the 4th control system slowly kicks in: the aero-control surfaces. Nothing special about them, they are the same aero-control surfaces found in each and every regular airplane. They permit control during atmospheric flight like any other plane, and allow the commander and pilot to steer the shuttle towards landing.
"So... they have engines during landing, right?"
NO. They have one shot, and one shot only, to land the shuttle safely. With no engines, the shuttle's like a big, heavy glider, relying on its speed and its aero-surfaces to stay up long enough and remain fast enough till it swoops down to a landing site. Repeat this again, one shot only. Of the 128 missions flown to date, of which 126 made it safely to landing ( the 2 exceptions are explained below), ALL 126 landed successfully. That's for those who complain that astronauts are overpaid. In my opinion, they are UNDERpaid.
The shuttle consists of several components, most notably the crew cabin, payload bay, the engines, which we already covered, the shuttle's robotic arm, and its TPS. The payload bay is for, of course, the cargo payload for that mission. The robotic arm is on the side inside the payload bay, used to grapple things like satellites or cargo. Takes extreme skill to operate it. TRUST ME. The TPS, or thermal protection system, is mainly on the underside of the shuttle, nose, and the leading edges on the wings. They consist of hundreds of reusable thermal tiles that protect the shuttle from the super-heated ionized air as it cuts down into the atmosphere at speeds over 20 times above the speed of sound during reentry. These tiles are resistant to heat, but are fairly fragile to impact damage.
The crew cabin consists of the flight deck, where the commander, pilot and 2 other crew members sit, the mid deck, where 3 other crew members sit, and personal and science cargo is stored, and the lower deck, where shuttle control electronics are stored.
To finish, a little bit of history. Run.
As of this date, there have been 6 built orbiters, but only 5 have been used for actual flights. Shuttle Enterprise was the very first shuttle, used for fitting tests and approach-and-landing tests, but never saw space. Columbia was the second shuttle, and the first to fly. Challenger followed, with Atlantis and Discovery completing the 4-shuttle fleet.
Unfortunately, Challenger was lost in a regrettable and tragic accident, just 73 seconds after liftoff on its ill-fated STS-51L mission, along with its crew (the would-be first teacher in space was on that flight) and cargo (the most important being a NASA TDR Satellite (or TDRS. Will explain in a later blog.)). One of the SRBs produced a leak, which was more like a flare, due to an overlooked design flaw, which burned into the external tank. At T plus 73 seconds (meaning 73 seconds after ignition and mission start) the SRB broke free of the external tank and collided with it, breaking up the entire system. Because of the already fast speeds they were going, the air pressure broke everything up that would otherwise be in a perfect orientation to allow good air passage, producing that image you see above. It was all over in less than a second. The two clouds jutting above the massive one are the SRBs, free of the external tank and flying crazily out of control, before the range safety console detonated them (more explanations about the different launch and f light controllers at a later blog). A very sad January 28, 1986.To replace Challenger, the youngest shuttle of the fleet, Endeavour, was made. The SRBs were corrected of their design flaws. The external tank was also revised. Several contingencies were created to prevent this, and any related accidents at liftoff. The crew even began to use full-pressure suits, as it was later discovered that some of the crew were still alive after the breakup, but suffocated due to air pressure loss, and... let's say fortunately, were unconscious the moment the cabin section of the broken orbiter hit the ocean at over 200MPH. They said this would give them a chance should cabin pressure loss should occur.
...they forgot about re-entry.
I remember this. February 1, 2003. I came home from college, turned on the TV, tuned into channel 4, and this video burned into my eyes. The fragments of space shuttle Columbia breaking up as they reentered the atmosphere.
Apparently, at launch, a piece of foam broke off the external tank and impacted the leading edge of the left wing, where most of the heat is concentrated on during reentry. At the speed they were going, a briefcase-sized chunk of foam (or, imagine your laptop, but made of foam) was as lethal as a car hitting you at over 100 miles per hour. This broke off several thermal tiles off the left wing's leading edge. Engineers voiced concern, but since this has happened before, albeit on lesser critical areas, mission management waved off those concerns. Unfortunately, the engineers' concerns came true, as during reentry, at the point of maximum heating of the critical areas, the spuer-heated air penetrated the leading edge, and started to break up the shuttle. When the shuttle lost all control, it pitched and rolled violently, exposing the more fragile parts of the shuttle to the high-pressure, high-temperature air stream. Within seconds, the shuttle broke up, becoming a mass of meteorites streaking across the Texas sky, still going at over 10 times the speed of sound. Even if they had bailed out on time, they were going at such an extreme speed, that if the high-pressure current didn't break them apart like paper, the high-temperature, ionized air would have burned them.
....astronauts who still brave the shuttle are sorely underpaid.
The shuttle fleet was grounded on both tragedies. Years passed, accident reports, investigations galore... in the post-Columbia scenario, they evaluated that there was nothing that could be done, due to the reasons stated above. So they opted for early failure detection mechanisms, and contingency plans to send a rescue mission while the orbiter with the failed TPS awaits at the International Space Station, by that moment operational, albeit much smaller than it is today. To detect any problems in the TPS, new, more powerful, higher resolution cameras were installed throughout the launch pad, and the orbiter was equipped with an extension to their robotic arm, called the Orbiter Boom Sensor System, or OBSS, which is maneuvered to aim below the orbiter to scan the underside for possible damage, both on the second day of the flight, and 2 days prior to the first scheduled deorbit burn. On missions that head directly to the ISS, the ISS crew members poise themselves on a window as the orbiter approaches. Once within 600 feet, the orbiter does what you may consider a backflip. It spins up, until the underside it in plain sight of the ISS, where the ISS crew takes a hundred and something hi-res images of the TPS, before the orbiter returns to it's upright opsition before initiating docking with the ISS.
After the tragedies, the next shuttle flight mission was called, on both times, the "Return to Flight" mission. After Challenger, almost 3 years later, on September 29, 1988, STS-26 was launched. After Columbia, on July 26, 2005, the more known second Return To Flight mission, STS-114, flown by ex-astronaut Eileen Collins, the first woman to be an STS mission commander, testing the new systems designed to prevent a second Columbia-like scenario. Guess which was the shuttle selected for both Return To Flight missions?
Discovery. My favorite orbiter. We're both the same age. Discovery just celebrated its 25th anniversary, and I'm also 25. Lol.
There's been several controversies in that the shuttle system is unsafe, and requires everything to be perfect to be able to commit to anything, be it launch, any inorbit operation, and of course, entry operations. Also, there's been speculation that the amount of money wasted in the shuttle era is substantially more than what was wasted in the Apollo era. Consider this: each and every piece of the Apollo vehicle, the one used to reach the moon, was expendable and non-reusable, meaning they were purchasing new rockets, new engines, new flight hardware, everything, with every launch, since everything either got lost in orbit, burned up in the atmosphere, or got lost in deep space. With the shuttle, only the external tank is expendable. The orbiters and the SRBs are reusable. But when something in the reusable parts breaks, ooooooooooooh boy..... not to mention that Apollo could land anywhere in the open ocean, provided a U.S. Navy Aircraft Carrier was close by to pick them up. The orbiter only has one single shot to land at one of 3 places, either Kennedy Space Center, or Edwards Air Force Base, California, or the last resort, White Sands Missile Testing Center. If all three, by any stroke of incredibly lousy bad luck, were under siege by weather conditions, our astronaut friends would run out of air and die, unless they decide to risk a landing at a non-supported airstrip, assuming the landing strip is wide and long enough for the orbiter. Thankfully, this freak event hasn't ever occurred.
...yet.
On my next blog, I'll talk about the milestones during a launch event.
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