The Insane Engineering of Re-Entry
Summary
TLDRThis script delves into the intricate engineering behind the Space Shuttle's re-entry process, highlighting its unique challenges and solutions. From the precise OMS engine burn to the heat-resistant materials and ingenious design, it details how the Shuttle withstood extreme temperatures and atmospheric conditions. The summary also touches on the Shuttle's aerodynamic flight capabilities and the meticulous landing procedures, showcasing the remarkable feats of aerospace engineering that made space travel and re-entry possible.
Takeaways
- 🚀 The Space Shuttle was a unique spacecraft designed to survive the intense heat of re-entry and transition to aerodynamic flight, requiring a balance between the design of an unpowered glider and a re-entry vehicle.
- 🔥 During re-entry, the Shuttle experienced temperatures up to 1650 degrees Celsius, necessitating specialized materials and engineering solutions to protect the aluminum airframe.
- 🛠 The Shuttle's re-entry began with a precise burn of the orbital maneuvering system engines to adjust its velocity and trajectory for atmospheric re-entry.
- 🌌 To manage the extreme heat, the Shuttle used a combination of a blunt body design for heat dispersion, specialized heat-resistant materials like reinforced carbon-carbon composites for the leading edges, and thermal protection tiles for the underside.
- 🛬 The Shuttle's design was influenced by the X-15, the fastest plane in history, which provided insights into hypersonic flight but also highlighted the limitations of certain materials and approaches for the Shuttle's re-entry system.
- ✈️ The Shuttle's wings and tail were carefully molded to generate lift and control during re-entry and transition to gliding flight, with a focus on the entry flight corridor for a safe descent.
- 🔄 The Shuttle faced a communication blackout during the peak of re-entry due to the plasma layer formed around it, which interfered with electromagnetic signals.
- 🛤️ The Shuttle's final approach and landing required careful management of its energy and trajectory, with the use of specialized training aircraft to prepare pilots for the unique challenges of landing a glider with no powered flight capabilities.
- 💺 The Shuttle's interior was protected from heat by a combination of heat shields, insulating tiles, and materials with varying temperature resistance, including silica fibers and nomex felt.
- 🔧 The Shuttle's maintenance and refurbishment between flights were simplified by the use of reusable and replaceable heat shield components, although the process remained complex and labor-intensive.
- 🖥️ The script concludes with a promotion for Onshape, a cloud-based CAD system that offers real-time collaboration and advanced design capabilities, highlighting a shift from traditional hand-drafting to modern digital design tools.
Q & A
What is the most difficult portion of the Space Shuttle Orbiter's mission?
-The most difficult portion of the Space Shuttle Orbiter's mission is the re-entry, where it has to journey through the earth’s upper atmosphere at extremely high speeds, creating a layer of superheated plasma around the aircraft.
How does the Space Shuttle manage to transition from re-entry to aerodynamic flight?
-The Space Shuttle manages to transition from re-entry to aerodynamic flight by carefully moulding its wings and tail, balancing the needs of an unpowered glider with the needs of a re-entry vehicle.
What is the purpose of the 2-4 minute burn of the orbital manoeuvring system engines?
-The purpose of the 2-4 minute burn of the orbital manoeuvring system engines is to reduce the orbiter's speed by just 0.1 kilometre per second, lowering its orbit enough to bring it into a collision course with the earth’s upper atmosphere.
What is the entry flight corridor and why is it significant?
-The entry flight corridor is a narrow window of speed and atmospheric conditions that the orbiter must navigate through during re-entry. It is significant because bleeding too little or too much speed can result in overshooting the window or catastrophic overheating.
What material was used for the Space Shuttle's airframe and why?
-The Space Shuttle's airframe was made from lightweight aluminium, which has a lower maximum operating temperature than Inconel X, but is much lighter, making it suitable for an aircraft designed to be carried to orbit.
Why was the ablative coating used on the X-15 unsuitable for the Space Shuttle?
-The ablative coating used on the X-15 was unsuitable for the Space Shuttle because it had a habit of burning away and attaching itself to the cockpit windows, potentially blinding the pilots, and it was not reusable, which would increase the cost of refurbishing the shuttle between flights.
How does the Space Shuttle protect its surface from the superheated plasma during re-entry?
-The Space Shuttle protects its surface by keeping the superheated plasma as far away from the surface as possible through careful design of the nose, wings, and belly to ensure shockwaves are kept at bay.
What is the role of the rear body flap during re-entry?
-The rear body flap serves as a massive control surface to manage the shuttle's trajectory during re-entry. It also doubles as a heat shield for the shuttle's main engines, protecting them from the heat of re-entry.
What material is used for the leading edges of the Space Shuttle's wings and why?
-The leading edges of the Space Shuttle's wings are made of a reinforced carbon-carbon composite. This material is capable of withstanding temperatures up to 1510 degrees Celsius, making it ideal for the hottest parts of the shuttle.
How does the Space Shuttle manage its trajectory to target its landing area during re-entry?
-The Space Shuttle manages its trajectory by banking, which splits the lift into vertical and horizontal components. This allows the shuttle to adjust its trajectory to target its landing area without lowering its angle of attack.
What are the challenges faced by the Space Shuttle during the final approach and landing?
-The Space Shuttle faces challenges such as managing its energy and trajectory in the absence of powered flight, dealing with the immense drag created by its blunt body design, and ensuring a safe landing on a precise runway from a high-speed glide approach.
Outlines
🚀 Space Shuttle Re-entry Engineering
The Space Shuttle's re-entry process is explored, highlighting its unique engineering challenges. After 7 days in orbit, the Orbiter begins its perilous journey through Earth's upper atmosphere, where it encounters extreme heat and friction, necessitating a specialized design. The Shuttle's ability to transition from a re-entry vehicle to an aerodynamic glider is underscored, with emphasis on the careful shaping of its wings and tail. The video details the critical OMS engine burn to adjust the orbiter's speed and trajectory for re-entry, and the importance of the entry flight corridor to avoid overheating or missing the atmosphere. The Shuttle's design, influenced by the X-15, had to overcome issues with ablative coatings and the limitations of using lightweight aluminum instead of heat-resistant Inconel X, is also discussed.
🔥 Thermal Protection Systems of the Space Shuttle
This paragraph delves into the thermal protection challenges faced during the Space Shuttle's re-entry. The nose and wings, being the primary heat shields, had to withstand temperatures up to 1650 degrees Celsius. The use of a blunt body design to create a bow shock wave and insulating air layer is explained, as is the Columbia shuttle disaster resulting from damage to the wing's leading edge. The development of the reinforced carbon-carbon composite for the leading edges is highlighted, along with the need for a non-conductive material to attach these heat shields to the aluminum frame. The use of insulating tiles, both low and high-temperature varieties, and their specific coatings for heat reflection or dissipation, is also covered, emphasizing the meticulous assembly and placement of these tiles for optimal protection.
🛠 Space Shuttle's Heat Shield and Structural Flexibility
The paragraph discusses the Space Shuttle's heat shield and the need for structural flexibility to accommodate thermal expansion during re-entry. The use of flexible nomex felt beneath the heat-resistant tiles is explained to prevent damage from the airframe's expansion. The importance of using a high-temperature adhesive to attach the tiles and the inclusion of expansion gaps to avoid breakage are highlighted. The paragraph also covers the use of flexible heat shields made from silica and nomex fibers for areas of lower temperatures and the unique control challenges of maintaining a 40-degree angle of attack at hypersonic speeds, including the role of the rear body flap as both a control surface and a heat shield for the main engines.
✈️ Space Shuttle's Aerodynamics and Landing Procedure
This section examines the Space Shuttle's unique aerodynamics and the complexities of its landing procedure. The need for large delta wings to achieve the crossrange capability is discussed, along with the Air Force's requirement for the shuttle to return to the launch site after a single orbit. The challenges of managing the shuttle's energy and trajectory for a precise landing are highlighted, including the use of banking to adjust lift and the peculiar control behavior at hypersonic speeds. The paragraph also describes the Shuttle's steep glide approach path and the use of speed brakes and rudder deployment for deceleration and landing, as well as the intensive training required for pilots to manage this unique aircraft.
🛫 The Space Shuttle Program and its Legacy
The final paragraph reflects on the Space Shuttle program, from its engineering marvels to its operational procedures. It discusses the program's inception, the unique design requirements, and the intensive training for pilots. The paragraph also touches on the contingency planning for potential abort scenarios and the support infrastructure at various landing sites worldwide. The narrative concludes with the shuttle's post-mission procedures, including the refurbishment process and the transportation of the orbiter back to Florida. The video script concludes with a nod to the evolution of design tools, highlighting the modern capabilities of computer-aided design and the advantages of cloud-based systems like Onshape.
🖥️ The Advantages of Cloud-based CAD with Onshape
The concluding part of the script promotes Onshape, a cloud-based CAD system, emphasizing its benefits for engineers and designers. Onshape's capacity for real-time collaboration, the elimination of version control issues, and its accessibility across various devices and operating systems are highlighted. The paragraph also underscores the system's ability to perform compute-intensive tasks like Finite Element Analysis and rendering in the cloud, thereby streamlining the design process. A special offer for the Onshape Professional Plan is mentioned, available free for up to six months, and an invitation to sign up using the provided link is extended to viewers.
Mindmap
Keywords
💡Space Shuttle Orbiter
💡Re-Entry
💡Orbital Maneuvering System (OMS)
💡Entry Flight Corridor
💡Reaction Control System (RCS)
💡Ablative Coating
💡Inconel X
💡Carbon-Carbon Composite
💡Silica Tiles
💡Elevons
💡Drag Shoot
Highlights
Space Shuttle Orbiter faces the most difficult part of its mission after 7 days in orbit: re-entry through the earth’s upper atmosphere.
The Space Shuttle was uniquely capable of surviving immense re-entry heat and transitioning to aerodynamic flight.
Re-entry involves a precise 2-4 minute burn of the OMS engines to reduce the orbiter's speed by 0.1 km/s.
The shuttle's wings generate lift during re-entry, crucial for avoiding overshooting or catastrophic overheating.
The entry flight corridor is a narrow window for a successful re-entry, avoiding speed extremes.
The Space Shuttle's design was influenced by the X-15, the fastest plane in history, for hypersonic flight understanding.
Inconel X, used in the X-15, was too heavy for the Space Shuttle, leading to the use of aluminum with a lower operating temperature.
Ablative coatings used in the X-15 were unsuitable for the Space Shuttle due to safety and reusability concerns.
The Space Shuttle's nose, wings, and belly were designed to minimize shockwave impact and associated heat.
Schlieren imaging reveals the effectiveness of the shuttle's design in managing shockwaves and heat.
The Space Shuttle uses a blunt body design to create a bow shock wave and insulating air layer, reducing heat transfer.
During re-entry, the shuttle experiences a communication blackout due to the plasma layer blocking electromagnetic signals.
The shuttle's body flap serves as a massive control surface and a heat shield for the main engines.
Reinforced carbon-carbon composite is used for the leading edges of the shuttle, capable of withstanding extreme temperatures.
Inconel attachment points and insulating tiles protect the shuttle's interior from the heat of re-entry.
The shuttle's tiles are carefully engineered and assembled like a puzzle, with specific shapes and thicknesses.
Nomex felt and flexible adhesive allow the shuttle's structure to flex without damaging the heat-resistant tiles.
Flexible heat shields made of silica and nomex fibers are used in areas of lower temperatures for easier replacement.
The shuttle's bank angle controls work in reverse at hypersonic speeds due to the interaction with compressed air.
Air data sensors are deployed at Mach 3 for the final approach, providing crucial flight data.
The Space Shuttle was designed with large delta wings to achieve the crossrange needed for a single-orbit return.
Pilots underwent intensive training using modified Gulfstream jets to simulate shuttle flight characteristics.
The shuttle's approach and landing procedure is carefully managed to ensure a safe touchdown on a long runway.
Onshape, the video's sponsor, offers a modern cloud-based CAD system for collaborative design work.
Transcripts
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After spending 7 days in orbit around the earth, the Space Shuttle Orbiter now has
arguably the most difficult portion of its mission to complete. A hell blazing
journey through the earth’s upper atmosphere. Where it will travel so fast that it will rip
air molecules apart, forming a layer of superheated plasma around the aircraft.
Re-Entry is where the Space Shuttle truly became a one of a kind spacecraft.
The Space Shuttle was a radical new idea. A spacecraft capable of
not only surviving the immense heat of re-entry, but capable of transitioning
to aerodynamic flight, which required careful moulding of its wings and tail,
balancing the needs of unpowered glider with the needs of a re-entry vehicle
This is the Insane Engineering of the Re-Entry
The Re-entry procedure begins with a 2-4 minute burn of the orbital manoeuvring system engines
while the space shuttle is upside down and travelling backwards.
With an orbital speed of around 7 kilometres per second, the OMS pods need to reduce the
orbiter's speed by just 0.1 kilometre per second. 1.3% of its velocity, to lower its
orbit enough to bring it into a collision course with the earth’s upper atmosphere.
A precise manoeuvre; bleed too little speed and the orbiter will overshoot its
narrow window for success, skimming through the thin upper atmosphere and potentially
bouncing back into space. The orbiter has wings that generate lift, after all.
Bleed too much speed and the orbiter will descend through the atmosphere too fast,
reaching the thick lower atmosphere before enough speed has been leached away,
resulting in catastrophic overheating. This narrow entry window was called the entry flight corridor.
Once the delicate retrofiring sequence has been completed. The next phase of re-entry
begins. The reaction control system flips the shuttle around and places it into a
40 degree upwards pitch angle, ready to meet the earth’s atmosphere. [REF]
Entering the upper atmosphere at 30 times the speed of sound. The speed is 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).
Nothing like this had ever been attempted. A blunt body capsule, like every other
re-entry capsule to date, designed purely for thermal protection is an engineering challenge,
but tack on the needs of an aircraft and the task gets vastly more difficult.
Thankfully NASA had a test run in 1959 with the X-15. The fastest plane in the
history of humankind, and it advanced our understanding of hypersonic flight,
providing many lessons that were incorporated into the space shuttles design.
However the X-15 had one major advantage over the Space Shuttle. It didn’t need to launch itself to
orbit. It didn’t even launch from the ground. Instead launching from the belly of a B-52.
This allowed the X-15 to use a state of the art advanced heat resistant aerospace metal,
inconel X, with a max operating temperature of 980
degrees celsius (1800 F). The Space Shuttle could not use this metal.
Inconel X is too heavy, about 180% heavier than an equivalent aluminium
airframe. A massive issue for an aircraft designed to be carried to orbit. [REF]
The Space Shuttle’s airframe therefore is not made from inconel X. It is composed of lightweight
aluminium, which has a max operating temperature of just 177 degrees. 5 times lower than Inconel X.
The orbiter would experience temperatures 10 times
greater than this for extended periods of its re-entry flight.
To make matters worse, one of the principle lessons learned during
the X-15 program was that the hot pink foam ablative coating sprayed onto the plane for
top speed flights was completely unsuitable for the space shuttle.
An ablative coating is a sacrificial material designed to gradually burn
and fall away from the aircraft, pulling the heat away with it.
However, the ablative coating of the X-15 had a nasty habit of burning away from the nose of the
plane, and begin attaching itself to the cockpit windows, rendering the pilots completely blind.
Which presented a bit of a problem. At one point the engineers of the X-15 considered
attaching a small explosive to the window, and intentionally exploding the outer pane of glass
to remove the ablative stained window, leaving only the inner pane for landing.
Thankfully they came up with the much less risky solution of installing a mechanical
eyelid to the left window that remained closed until the high speed portion of
the flight concluded. Providing the pilot one clean window to land with. An extremely
primitive solution that created stability issues as the open eyelid acted like a canard,
causing the plane to pitch up, roll right and yaw right.
Even more terrifyingly, this coating became explosive when mixed with liquid
oxygen and could be triggered by even a slight impact. A massive safety concern
for a plane that required a liquid oxygen oxidizer to operate. A danger that would
be multiplied many fold with a vehicle filled with half a million litres of liquid oxygen.
The ablative was also not reusable, which would drastically increase the cost of
refurbishing the shuttle between flights.The space shuttle would need to be better.
As the space shuttle descended through the atmosphere its nose
and wings bore the brunt of the re-entry heat.
The high pressure shock waves forming around them have created a layer of superheated plasma,
if this heat managed to find its way into the delicate aluminium framework inside the orbiter,
it would be game over. This is exactly what happened to the Columbia shuttle
as a result of damage to the leading edge of these wings.
The first step to protect the orbiter's surface was to keep
this super heated plasma as far away from the surface as possible. The nose,
wings and belly of the orbiter was carefully crafted to ensure shockwaves were kept at bay.
We can see how using schlieren imaging. A pointed missile-like vehicle pierces
through the air with efficiency and in doing so creates a shock wave,
attached to its nose at an angle determined by its mach number.
This shockwave is simply a region of incredibly high pressure,
and with that pressure comes incredibly high temperatures
This can have disastrous effects, as DARPA experienced twice in 2010 and 2011 when
testing their sharp nosed hypersonic reentry vehicle. The HTV-2. Within 9
minutes of re-entering earth's atmosphere, both vehicles disintegrated as a result of
the 1930 degree heat penetrating their metallic skin. The HTV-2 completed its
mission of collecting hypersonic flight data, but the space shuttle needed to
not only survive this mode of flight, but to do it repeatedly with minimal refurbishment.
A good portion of this heat could be kept away from the aircraft skin with
blunt body design.Which creates a rounded bow shock wave with a layer of insulating
lower pressure air between the vehicle and the shockwave. Reducing heat transfer rates.
For this reason the Space Shuttles surface is carefully moulded to take advantage of this
phenomenon. The rounded nose cross section gradually transitions to a blunted triangle.
This shape minimised the heat reaching the less protected side wall of the shuttle,
which used lower temperature insulation.
We are now 7 minutes into the re-entry procedure, having descended 50 kilometres in altitude,
but only shedding 0.5 kilometres per second off our velocity, we have entered the period
of maximum reentry heat. A confluence of speed and atmospheric density.
The layer of superheated plasma surrounding the shuttle is blocking communication to the
computers and astronauts inside. A result of free electrons in the plasma interfering
with electromagnetic communication techniques. A problem that would last for the next 12 minutes.
For now the shuttle is operating on its own telemetry data. Ensuring that a 40 degree angle
of attack is maintained. Managing that angle with a velocity of 6.5 kilometres per second was no
easy task. A massive control surface was needed. The elevons on the outer wing would not suffice.
This is where the rear body flap came into play. It was a massive control surface
underneath the shuttle's main engines, covered in high temperature insulation.
The body flap doubled as a heat shield for the shuttles
main engines. With no cooling liquid hydrogen running through the nozzle,
the flap was needed to shield the engines from the heat of re-entry.
On the Space Shuttle’s third flight the Kuiper Airborne Observatory flew underneath the orbiter
as it re-entered and captured an infrared image of its searing hot belly. An experimental program to
validate NASA’s newly developed computational calculations and experimental testing.
This is what it saw [REF] The nose and leading edges are a scorching 1500 degrees celsius. Far
beyond what the Aluminium airframe underneath is capable of enduring.
These leading edges, experiencing the hottest temperatures, needed the most heat resistant
material on the entire shuttle, a reinforced carbon-carbon composite. One of the amazing
materials created in the years between the development of the X-15 and the Space Shuttle.
A carbon composite manufactured with a special post processing step.
It was initially manufactured like any other carbon fibre part. A carbon fibre
weave moulded into shape and bound together with a resin. However,
the heat of re-entry would set the hydrocarbon resin on
fire without special treatment. The post processing step would solve this problem.
The carbon composite is placed in a vacuum chamber and heated, causing
the hydrocarbon resin to decompose, releasing the hydrogens, leaving layers of pure carbon
behind. Graphite. Carbon fibres bound together by a maze of graphite. Strong, and capable of
withstanding 1510 degrees celsius. They face head on into the inferno of hypersonic flight.
The leading edge of the orbiter's wings is composed of 22 of these carbon carbon
panels. With sealing strips covering expansion gaps between each panel,
an essential solution to a lesson hard won during the development of the X-15.
To investigate the heat of hypersonic flight the X-15 was painted with a
special kind of paint that reacts to heat, and after one flight the X-15 returned with
strange wedge shaped patterns emanating from the leading edge expansion joints.
Small gaps in the leading edge to allow the inconel skin to bend and contort with the
wing without buckling. This localised heating was happening as a result of turbulent flow,
increasing the rate of heat transfer to the metallic skin of the aircraft. To fix
this small floating strips of inconel were placed over the expansion gaps..
These strips of reinforced carbon carbon serve the very same purpose.
However, there was one more problem. Carbon is a
thermally conductive material, not ideal for a heat shield.
The space shuttle has been travelling through the atmosphere for 15 minutes,
but is still travelling at 6 kilometres per second and contact has not been
reestablished through the cloud of plasma surrounding the aircraft.
This is a sustained heat, and with carbon being conductive,
this heat could make its way to the aluminium airframe over this period of time.
If these carbon carbon shields were attached directly to the airframe the heat would come
into direct contact with the metal, raising it above its max operating temperature.
To prevent this the panels were fitted with inconel attachment points that attached to the
aluminium airframe with inconel bolts. Inconel, being mostly made of steel,
is a poor conductor of heat and could handle the heat the carbon parts transferred to it,
without easily transferring that heat to the aluminium.
This wasn’t enough to protect the interior of the shuttle however,
a layer of insulating tiles were placed underneath the carbon carbon shield too.
The same insulation that was used on the underside of the entire orbiter.
The Space Shuttle Columbia had 32000 of these tiles, in two flavours, low temperature and high
temperature, white and black. Both of these tiles were made from the same base material.
Silica fibres just a few millimetres thick, which by volume made up just 10% of the tile,
the remaining 90% was nothing by air. An excellent insulating material,
a thick and light tile, composed of a material with a high operating temperature.
The coating is where the tiles differ. The black tiles, installed on the lower portion of the
shuttle, were covered in a black borosilicate and tetraboron silicide glass coating.
This black coating helps dissipate heat before it can conduct into the vulnerable
inner structure. Black for the same reason the SR-71 is black. Kirchoff’s Rule of Radiation.
This rule tells us a good infrared heat absorber,
basically any black object, is also an equally effective heat emitter. With the heat gained
from hypersonic flight vastly higher than the heat gained from solar radiation, it’s
preferable to prioritise outward heat radiation, than minimising heat gained from solar radiation.
So why isn’t the entire space shuttle black, like the SR-71?
The shuttle has one important difference with the SR-71, it exited earth’s atmosphere. Once outside
the earth's atmosphere the intensity of solar radiation increases drastically, with the longest
orbiter mission at 17 days, this heat had plenty of time to conduct through to the people inside.
The orbiter did have huge radiator panels to reject heat to space, but to minimise their
size we want to reflect as much of that heat back into space, and for that reason they are white.
These tiles were coated with a similar glass coating,
but with an aluminium oxide additive to provide the white colouring. The
coatings also helped to waterproof and strengthen these porous tiles.
The tiles were assembled like a giant precisely engineered puzzle with 32,000 pieces. Each tile
assigned a serial number that corresponded to their location, shape and thickness.
The tiles were created by mixing cotton like silica fibres with water, this mixture was
then cast into large blocks, and were then dried in a microwave oven. Once dried they
could be cut into smaller sheets. [Footage] The tiles varied from 25 millimetres to 127
millimetres thick. With the 127 millimetres tiles insulating up 1280 degrees celsius.
These sheets were then into their precise shapes,
according to their assigned serial numbers, using a computer controlled milling machine.
We are now coming through the end of the communication blackout, and enough
of the heat of re-entry has reached the aluminium airframe to cause it to expand. A major problem as
these tiles are not flexible in the slightest, and are quite fragile. The expanding airframe
could easily break the tiles and open up a path for the superheated gas to penetrate inside.
The engineers needed a way to allow the structure to
move beneath the tiles without causing the tiles to pop off.
To do this, the tiles were first glued in groups to a layer of flexible nomex felt.
This nomex fabric allowed the structure beneath to flex, expanding the lower side of the felt,
without transferring that strain to the upper layer attached to the tiles.
These tiles and felt were then attached to the shuttle using the same adhesive.
A commercially available high temperature RTV adhesive. A bright red silicone based adhesive.
To prevent collisions between tiles,
gaps between 0.64 millimetres and 1.9 millimetres were included.
Thankfully the issue of turbulent flow created by expansion gaps primarily affected the leading
edges of the wing, so these gaps were not covered on the exterior of the shuttle.
In areas exposed to lesser temperatures flexible heat shields were used. Constructed from high
temperature silica and nomex fibres to create a flexible fabric which were sewn together
with the same fibres, giving a quilted blanket appearance. With the nomex fabric capable of
resisting temperatures up to 370 degrees and the silica fabric capable of tolerating temperatures
up to 650 degrees. These were lighter and easier to replace than the tiles. Being
bonded directly to the structure once again with that bright red silicone RTV adhesive.
We are now out of the communication black out and approaching 4 km/s or mach 12 in velocity
and are about 45 kilometres in altitude. About 4 times the cruising altitude of an airliner.
The orbiter has maintained that 40 degree angle of attack this entire
time. [Page 239]. Being forced to hold an angle of attack this large comes with some
control problems. The orbiter needs to land precisely on a landing strip from
orbit. Managing its trajectory while being stuck with its nose up would be difficult.
Especially for a glider with no way to add energy once its been bled away by drag.
If the Space Shuttle wanted to lower its lift and lower
its altitude faster it could not lower its angle of attack,
So the shuttle needed a special way to adjust its trajectory to target its landing area.
Instead the orbiter decreased its lift by banking. This split
the lift into vertical and horizontal components. Reducing the lift keeping
the shuttle in the air and trading it for lift that moved it sideways.
This is what a typical re-entry flight profile looked like. This line is the angle of attack,
keeping steady up until Mach 12 and then gradually reducing as it
descends through the thick lower atmosphere. And this is the bank
angle. As the orbiter crashes down from orbit, it banks wildly from side to side.
The astronauts inside, who are already pointed 40 degrees up, are not tilted
on their sides up 70 degrees. The orbiter is essentially doing the fastest drift in history.
There are some quirks of flying this high in the atmosphere at hypersonic speeds.
The bank angle controls actually work in reverse to normal. If we deflect the right elevon down,
it should increase lift on the right wing and cause that wing
to rise, banking the aircraft anti-clockwise, but it doesn’t.
When the elevon is deflected downwards, into the already compressed hypersonic air it causes drag
to rise on the outer wing. This causes the orbiter to turn its nose in that direction.
As the nose turns in the direction of the deflected elevon, it shields that wing
and causes a decrease in lift, causing the shuttle to bank in that direction.
So, where a downwards deflecting elevon would typically cause an increase in lift on the wing,
here, through a series of events, it causes a decrease. Working in reverse.
Ofcourse this bank angle causes the Orbiter to drift off target
for its landing and to correct it needs to bank the other way.
The orbiter has now slowed down to Mach 3,
and at this point flight crew deploy air data sensors to aid in the final approach. [Page 418]
Two probes rotate from underneath the heat shield on either side of the nose,
providing air speed, angle of attack and temperature data to the flight computer.
At this point the orbiter is flying like a plane, but it’s not a plane, it's a glider
and the flight crew needed to carefully manage the remaining energy to land safely.
Especially as the orbiter is not built like a traditional glider. Balancing the need to
survive reentry, while maximising lift efficiency was a unique engineering challenge, made more
difficult by Air Force funding causing the design to skew closer to a plane than a re-entry vehicle.
Early concepts of the shuttle drew inspiration from the X-15,
with much smaller wings. More than enough to land the original smaller orbiter on a runway.
The air force wanted a larger payload capacity,
and they had one more specific requirement that required bigger wings. They wanted
the Space Shuttle to be able to take off from Cape Canaveral, complete its mission,
and land back at Cape Canaveral after a single orbit. Essentially treating
the space shuttle like a military operation to avoid Soviet attention, fast and elusive
This came with some issues.
A single orbit took 90 minutes, in which time the earth rotated below the shuttle’s
orbit by 2000 kilometres. So, to return to its launch location the orbiter would
need to be capable of flying laterally by at least 2000 kilometres. This is called
crossrange. The original X-15 inspired design was capable of just 370 kilometres of crossrange.
North American Rockwell proposed this huge blended body delta wing concept in 1970
which would have given the orbiter 2800 kilometres of crossrange (1500 nautical
miles). The full reusable concept, with its crewed booster rocket and
internal fuel tanks were not to be, but the large delta wings endured.
These delta wings provided enough lift in both hypersonic, supersonic and subsonic flight
regimes to provide the cross range needed to reach the original launch site after a single orbit.
Despite that, the space shuttle was an unwieldy aircraft, and with no powered flight,
the commander had one shot to land it safely. So they had to go through intensive training.
In 1973 NASA created 4 training aircraft by modifying 4 gulfstream jets to fly like the
space shuttle. [REF] In order to mimic the immense drag the blunt body design of the
space shuttle would create, the gulfstreams flew with their landing gear down, with their engines
working in reverse, and flew with their flaps deflected upwards to decrease lift. [Footage]
With flight characteristics like this the space shuttle needed to carefully manage
its energy. Losing too much altitude far from the runway would be far from ideal.
The pilots aim, guided by beacons and ground control, for a tangential entry
into a circular approach path 5800 metres in diameter just off the runway. The
moment they intercept this circle the space shuttle commences a deep spiralling turn.
At this point the space shuttle is still travelling at about 0.8 mach. Still very fast,
and it's at this point the wings are stressed the most. Hitting a higher max dynamic pressure
than at any point during the re-entry process due the higher air pressure at this altitude.
And the shuttle's descent rate increases,
now losing altitude rapidly with the knowledge the runway is within a safe gliding distance,
descending to about 3000 metres in altitude and slowing to about 0.5 mach.
At this point the Shuttle enters a straight
20 degree glide approach path. Much steeper than any airliner.
Bleeding speed as needed using the split rudder speed brake. The rudder
on the vertical tail wasn’t just used for controlling yaw by deflecting left and right,
it could split in two, deflecting outwards to a maximum of 62 degrees on either side.
The gear is lowered as late as possible and in the final moments before touching
down the commander will increase the angle of attack of the shuttle using
the elevons in order to slow its descent rate before touching down.
At the moment of main gear touch down the speed brake is commanded to fully
open. At this point the shuttle is still travelling at 360 kilometres per hour,
close to 0.3 mach, and there is plenty of braking left to do.
The runway at Cape Canaveral is 4.6 kilometres long, much longer than your average runway. With
typical 3 kilometres long runways being able to deal with the heaviest of jumbo jets landing.
As the nose gear touches down the electro-hydraulic brakes in each of
the 4 main landing gear wheels are fully engaged by application of the foot pedals in the cockpit.
Each brake assembly had nine carbon-lined beryllium discs,
four rotors, and five stators, which were pressed together to provide braking force.
On STS 49, Bruce Melnicks mission, an additional braking mechanism was introduced,
hidden away underneath the vertical tail speed brake. The drag shoot. STS 49 was the maiden
flight of both the endeavour and the drag shoot. An explosively deployed parachute, you
can even see the parachute door and sabot being flung from the back of the shuttle on landings.
It was designed to allow the Space Shuttle to land on a shorter 2500 metre runway,
a contingency plan in the event the space shuttle had to abort
a launch and land on a runway on the other side of the atlantic.
For each and every launch NASA sent staff to these predetermined landing locations,
like Fairford RAF base in Gloucestershire,
England. A large team was needed to assist with the final moments of each space shuttle mission.
And these teams were not once needed in the entire history of the space shuttle program.
A giant fan was even rolled out on the runway to help disperse any potential toxic chemicals,
like the hydrazine fuel, away from the shuttle. [FOOTAGE]
The mission is now over. The crew has disembarked and the space shuttle will be refurbished and
flown back to Florida on the back of a 747 in preparation for its next mission.
People often say how incredible it is that older aerospace and aviation projects like
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and a labour intensive art form at that.
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