One of the most impressive sights of recent years was the synchronized
landing of the Falcon Heavy boosters and although the center core didn't make it
back simply because it didn't have enough ignition fluid to restart all
three of a centre cores engines the overall mission was a success.
But SpaceX wasn't the first to use this technique and as we will see there are
several other ways to get launch assets back to earth safely without just
letting them burn up in the atmosphere. The maneuver which SpaceX use is known
as a fly back and it requires the perfect coordination of nitrogen cold
gas thrusters, gimballed engine burns and the constant adjustment of the four grid
fins the heat-resistant control surfaces to fine-tune the Falcons flight path. The
first stage of a falcon 9 weighs over 14 tonnes with empty fuel tanks but it
can fly with the greatest of precision to land safely from the edge of space
separating from the second stage at hypersonic velocities and at an altitude
of more than 70 kilometers the Falcon 9 navigates through unpredictable
high-altitude atmospheric weather conditions to land at a precise spot on
the Earth's surface. One other rocket can perform a similar feat and that's new
Shepard, a sub orbital booster built by Jeff Bezos's Blue Origin. New Shepard
is decorated with the image of a giant feather which according to Bezos is a
symbol of the perfection of flight. On November 23rd 2015 new Shepard became
the first rocket to fly to space and return to make a vertical landing. Less
than a month later on December 21st 2015 SpaceX's Falcon 9 became the first
booster to launch a payload to orbit before returning also to land
vertically, the age of reusable rockets had begun but why did it take so long to
see it happen. Landing a rocket presents some serious technical challenges but
the underlying reason for the delay has been the limited market for orbital
launches. In the past the launch industry was controlled by national and
international space agencies, even rich governments have often lacked the
resources to fund innovation in space technology, repeated launch failures of a
government-funded prototype with usually result in the project being canceled and
this is exactly what has happened to many of the 20th century's most
brilliant machines that we often talk about on this channel. Jeff Bezos and
Elon Musk have invested their personal fortunes
into reusable boosters with the expectation that in reducing the cost of
each launch the market will grow. SpaceX and Blue Origin
are filling a niche which has been left open by the national space agencies but
reusable space vehicles were a priority for NASA since the 1970s however once
the Space Shuttle was selected America was stuck with a design for a generation
and they're gliding orbiter turned out to be hugely expensive and only grew
more inefficient as they aged. On the other side of the Iron Curtain there was
a similar story the Buran the Soviet space shuttle also became an
all-consuming project that the USSR ultimately couldn't afford but why did
winged space planes do such a poor job of being what they were supposed to be a
reusable affordable launch system. The inefficiency of a shuttle design can be
traced back to the decision to carry a large set of wings and engines into
orbit, the American space shuttle weighed 68 tons and the Buran weights 62 tons
and both could deliver a payload of less than 30 tons to low Earth orbit this
meant that any payload delivered by the shuttle or Buran had to be lifted with a
vehicle that tripled the total mass to orbit and that was without the booster
rockets and the fuel tanks and everything else
required to get them there. Ironically the extra weight of the crew quarters
wings and heat shielding also made the manned shuttle a dangerous way to get into
orbit for every ton you accelerate to orbital velocity you then need to
decelerate a ton of mass during reentry through friction with the atmosphere
this process generates a lot of heat and the heavy of a vehicle the more easy
creates. The shuttle and Buran dealt with this problem by being large and mostly
Hollow at the point of reentry increasing the surface area per ton for
atmospheric braking but another set of space planes reduced the aerodynamic
pressures of reentry by simply carrying a less mass into orbit small space
planes have been in development since the X-20 dinosaur first outlined in 1960
and 21st century robotic orbital vehicles can do more with less mass.
Without the need for crew quarters or life support they can carry an even more
economical payload fraction. America has two high-profile robotic space planes in
development right now the Boeing X-37 or orbital test vehicle and the Sierra
Nevada corporation's Dream Chaser both of these launch vertically and then
re-enter the atmosphere and glide to a horizontal runway landing. Not to be
outdone China is also working on a space plane called the "Shenglong" or divine
dragon. Shenlong is aerodynamically similar to the x37 but has only appeared
so far as a scaled-down version for a 2007 drop test from a Chinese Air Force
H6 bomber but while small space planes continue in slow development reusable
boosters have been studied for decades sometimes adding a long-range fly back
capability beyond anything possible with a falcon 9 or the new Shepard. The second
generation of the Energia program, that was the rocket which was to carry the
brand Soviet Space Shuttle was codenamed "Uragan" or "Hurricane" and was planned as
a fully recoverable vertical take off an horizontal landing
system. Like the original Energia rocket Urgan would use strap-on boosters
powered by the four chamber RD-170 engine the RD-170 was ahead of its time
and designed to ignite up to 10 times and achieving up to 20 relights in tests.
Soviet engineers realized that this relight capability made the any gear
boosters suitable for reusability over many launches. When the Urgan's boosters separated from my main stage, it would unfold a set of wings to slow for
re-entry and then maneuver for a horizontal landing on a runway. The
center core of the Urgan was also to be fitted with wings a bit like the
Buran and this was to return to earth using the same technique as the
antipodal bomber, a design first proposed by Eugene Saenger in 1943. This would have
the center core skip off the upper atmosphere around the globe until it
returned back to its launch site where it would then land like the Buran itself
on a runway. Although the antipodal design was not
followed up the winged booster design was too good to abandon and it
reappeared after the fall of the Soviet Union as proposed booster for the Angora
system. The fly back booster was called Baikal and was essentially the same
concept as the Urgan fitted with folding wings and an air-breathing RD-33
jet engine for atmospheric flight. A similar system was also studied by the
German Aerospace Center the DLR from 1999 to replace the expendable solid
rocket boosters on the Ariane 5 launcher. Each liquid fueled fly back
booster or LFBB had forward canards small rear wings and a turbofan engine
giving the booster all the aerodynamic capabilities of an aircraft. The LFBB
design progressed as far as scale models before being cancelled apparently
because the hardware was becoming too large and complex to justify the
economic savings. But ESA has recently funded a new
reusable first stage booster designed at Airbus to work with the upcoming Ariane
6 launcher. The Advanced Expendable Launcher with Innovative Engine Economy
or ADELINE uses an unusual set of aerodynamic features to potentially
achieve the most efficient and capable fly back yet. Once the first stage fuel
is expanded Adaline separates and reenter to the atmosphere protected from
the heat by the shield in the nose. Once in the denser part of the atmosphere the
booster uses wings and a pair of propellers to maneuver to a horizontal
landing on a runway. Propellers can achieve even better efficiencies than
jet engines meaning that even less fuel needs to be reserved for the fly back.
Now something which SpaceX is doing is forcing the rest of the launch industry
to re-examine their use of non reusable launch systems. A few years ago the
Russian space agency, Roscosmos said that they didn't see any point in developing
reusable rockets but after the recent success of SpaceX and their growing
share of a market, Roscosmos is now say they are actively looking at
reusable rockets so expect to see a lot more in the way of rockets and boosters
flying back to base by themselves. So what do you think of SpaceX and Blue
origins vision of a reusable future, let me know what you think in the comments.
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