Reusable Spacecraft Launch Vehicles

Estimated Video Length: 18-20 mins
/Title screen/

/Intro - Brief intro to space exploration & orbits/
For centuries Humans have been interested in learning about the wonders of Space but it wasn’t until the 20th century that we were able to learn about space from space.
The first man-made object to reach space was a V-2 missile, number V-177, launched by German scientists on 20th June 1944. Number V-4 was at the time considered to be the first rocket to reach outer space however it only reached an altitude of about 90km, below the Karman Line [1] - which is considered to be the point where space starts. [11] It wasn’t until 4th October 1957 that the Soviet Sputnik 1 became the first satellite to achieve orbit. [2]
The first man to both go to space and orbit Earth was Soviet pilot and cosmonaut Yuri Gagarin on 12th April 1961, aged 27. Gagarin was in space for 1 hour and 48 minutes aboard Vostok 1 before safely returning to Earth. [4]
Since then there have been hundreds of missions with the aim of learning more about space, including the Apollo moon missions, planetary landers and rovers, space stations and deep space probes.

There is a difference between going to space and getting into orbit though. If you launched a rocket straight up to higher than the Karman Line at roughly 100km then that rocket would be considered ‘in space’, however just like when you throw a ball up in the air, the rocket will just fall back down again. Getting into space is relatively easy, amateur rocket enthusiasts have even achieved it but getting into orbit is much harder. To get into orbit you actually have to travel sideways not upwards; the reason you go upwards is to avoid obstacles such as mountains and more importantly to get out of the atmosphere. Below about 160km above sea level the atmosphere is too thick to maintain orbit as the air will slow down the rocket [5], the rocket would have to be constantly burning its engines to maintain orbit, which would require an unfeasible amount of fuel. A simple way to understand how orbits work is to imagine that the rocket is constantly falling towards the Earth but it’s also moving forwards so quickly that by the time it would hit the ground, the Earth has curved away beneath it.

Here is an animation to demonstrate this more clearly. The red dot represents an object trying to achieve orbit. As you can see in the first two attempts it is moving too slowly so it falls and impacts the ground; however going faster the second time, it travels further. On its third attempt you can see it has travelled fast enough that by the time it would hit the ground, the Earth has curved away beneath it. The object has not slowed down though because it is above the thickest of the atmosphere. This means that the object will continue to follow the same path until it is either slowed down or accelerated which is what leaves it in orbit.

/Intro – Intro to launch vehicles/
When a satellite or other payload is put into space, it is launched on what is known as a launch vehicle, or launcher. To maintain low Earth orbit, which is between 160km and 2000km, the satellite must be moving at at (repeated word not an error) least 7km/s which is over fifteen and a half thousand miles per hour [5] – though the exact speed depends on the target orbit; this is the reason rockets are so large.
The tallest, heaviest and most powerful launch vehicle ever used is the Saturn V, the launcher used by NASA during the Apollo program at 110.6m tall, 10.1m in diameter and weighing in at almost 3,000 metric tonnes at launch. The cost per launch of the Saturn V was just under $500 million dollars in 1964-73 which has been estimated to be around $3.2 billion in the present day. [6]
The mass of Apollo 11 was about 45.7 tonnes at launch [7], only about 1.5% the mass of its launch vehicle, the launch vehicles make up the vast majority of the mass of launches but when considering research costs, construction, materials/resources etc. they are usually cheaper than the payload. As launch vehicles are relatively cheap, in the past it has not been worth the cost of researching and testing reusable launch vehicles as the technology was too advanced.

/Intro – Need for reusable launch vehicles/
It is becoming much more viable, and even more of a necessity, now to develop reusable launchers as it can massively reduce launch costs. It’s the same principle as aeroplanes, a plane is not destroyed after one flight. If they were then the cost of flights would be too high for most people to afford. For private space companies, the cheaper they can make their vehicles to launch, the more customers they are likely to get – provided it doesn’t increase the chance of a failed mission. It is mostly private companies that are developing reusable launch vehicles for this reason.

/Space Shuttle – Intro/
The Space Shuttle, officially named the ‘Space Transportation System (STS)’ is the most well-known reusable launch vehicle being in use from 12 April 1981 to 21 July 2011. [8]

/Space Shuttle – Demo/
//DEMO VIDEO PLAYING IN BACKGROUND//
The space shuttle would launch vertically attached two a large fuel tank and two solid rocket boosters (SRBs). The shuttle itself didn’t carry fuel for the main engines, it all came from the external tank. [12] The Shuttle lifted off with over 30,000 kN of thrust [13], which is the equivalent thrust of over 25 Boeing 747s. [14]
Two minutes after launch, at about 46km, or 150,000ft, the two SRBs were jettisoned. They would then descend under a parachute and land in the sea where they would later be recovered to be used again. [13]
About 10 seconds after ‘Main Engine Cut Off’ the external tank would jettison but would not be recovered as it broke up in the atmosphere before impact. The shuttle used small thrusters called the ‘Orbital Manoeuvring System (OMS)’ to complete its orbital insertion. These would also be used to make adjustments to the orbit and to de-orbit the shuttle at the end of its mission. [15]
When the shuttle was in the appropriate orbit, it would release its payload. The shuttle was also used to rendezvous with the International Space Station to deliver crew and payloads and was used to launch and work on the Hubble Space Telescope. [16]
When the shuttle had completed its mission in orbit, it would deorbit and re-enter the atmosphere at over 20 times the speed of sound, creating an extreme amount of heat from the friction. The bottom of the Shuttle is made up of heat resistant carbon tiles to prevent damage. This is what was damaged on the Columbia Shuttle which caused the Shuttle to disintegrate on re-entry, killing all 7 crew members. [18]
The shuttle would then glide down and land on a runway like any other plane and would deploy a parachute to slow it down. At this point the shuttle could be recovered and serviced to be used again.

/Space Shuttle – Success or Failure? /
Despite having over 130 successful missions [17] the Shuttle Program was not considered a success by many people. The total project cost of the Space Shuttle Program was over $200 billion [8]; for reference the Saturn V’s project cost was $6.4 billion in its time, or about 41 billion in the present day. [6] The cost of a shuttle launch also cost between 450 million and 1.5 billion dollars [8] so despite its reusability, it still cost a lot of money. Although only capable of carrying about half the payload mass, SpaceX’s Falcon 9 launcher, currently costs about $61 million per launch. [9] Falcon Heavy, expected to launch in 2016 will cost $90 million per launch and will be capable of carrying almost double the payload mass of the Space Shuttle. [10]
The originally envisioned costs of Shuttle launches was about $54 per kilogram of payload, which is the equivalent of about $300 today. By 2011 the estimated cost of Shuttle launches was approximately $18,000 per kilogram[19], that’s 60 times the original planned cost.
The Space Shuttle is considered to have failed to achieve its promised cost and utility goals, as well as design, cost, management and safety issues by many people. [19]
The Shuttle was also originally said to be capable of launching every week however shortly after the Shuttles were first used it was realised that this was an unrealistic expectation. Over 30 years 125 missions were launched, averaging to roughly one launch every 3 months. [19]
Although technically reusable, the Shuttles were practically rebuilt after each launch.   The main engines were very complex and required a lot of maintenance; after each flight they had to be removed and thoroughly inspected. Before the engines were upgraded to what were known as the ‘Block II’ engines, the turbopumps (part of the engine for pumping the fuel) had to be removed, disassembled and overhauled after each flight. [19]
Because in many cases there would be no way to abort the launch and ensure survivability of the crew, such as in the event of a failure with an SRB, it was imperative that all systems worked perfectly without fail. This lead to a labour cost of about $1 billion per year for around 25,000 workers in Shuttle operations. [19]
In a 2007 paper, Dr Michael D. Griffin, the administrator of NASA at the time - which is the highest rank in the organisation - argued that if the Saturn was continued it could have provided six manned missions per year, two of them to the Moon, at the same cost as the Shuttle program, with the additional ability to launch infrastructure for further missions. [19] In the same paper he also said
“If we had done all this, we would be on Mars today, not writing about it as a subject for “the next 50 years.” We would have decades of experience operating long-duration space systems in Earth orbit, and similar decades of experience in exploring and learning to utilize the Moon.” [19]

/SOAR – Intro/
SOAR is a partially reusable launch system concept from Swiss Space Systems (S3) that is currently in development. It’s similar to the Space Shuttle but smaller, unmanned and launched atop an Airbus A300. This type of launch vehicle is officially known as a spaceplane. [20]


/SOAR - Demo/
//DEMO VIDEO PLAYING IN BACKGROUND//
SOAR will begin attached to the top of an Airbus A300 which will take off from a standard runway. After reaching sufficient speed SOAR will disconnect and continue to accelerate and climb towards space whilst the A300 returns to land.
Inside SOAR is a third, expendable stage which has been contracted to be developed by the Russian firm, RKK Energia. With this third stage, SOAR will be capable of launching up to a 250kg payload to LEO. [21]
At about 80km the third stage will be deployed and SOAR will glide back down to land on a runway where it can be recovered and prepared for another flight. [21]
The third stage will then carry the payload into orbit before releasing it and returning to Earth where it will burn up in the atmosphere.

/SOAR – Progress/
S3 plan to focus on assembly, integration and ground testing of its small satellite launcher in 2016 and ‘17 before testing a full flight of SOAR in 2017. This in preparation for its first commercial launch in 2018. An S3 spokesperson said “We are in the last year of our research and development program” in January of 2015. [21]
S3 plans to spend 250 million Swiss francs, which is about $247 million to cover all costs up to the first small satellite launch. [20]
Head of S3 USA Holdings Inc. said the list price for a launch to take up to 250kg to LEO up to 700km would be 10 million Swiss francs - or about $9.86 million. [20]
S3 had said they were going to offer zero-g flights in 2015 in order to gain employees experience operating the A300 as well as creating revenue for the company. [20] These flights have since been postponed due to ‘serious financial difficulties that include missed pay checks for salaried employees’. S3 have also said they ‘offered to certain customers to convert their zero-g tickets into company shares’. [22]
In the next few years we will see if S3 overcomes this set back in order to provide cheap launches for many companies with small payloads.

/ULA SMART Reuse – Intro/
United Launch Alliance (ULA) is a joint venture of Lockheed Martin Space Systems and Boeing Defence, Space & Security. Founded in 2006, ULA provide spacecraft launch systems for US government launches including for NASA and the Department of Defence. [23]
ULA recently released their concept of partially reusable launch system dubbed SMART Reuse, or Sensible, Modular, Autonomous Return Technology [23] which is intended to be used on their next launch vehicle ‘Vulcan’.  [24]

/ULA SMART Reuse – Demo/
//DEMO VIDEO PLAYING IN BACKGROUND//
The Vulcan launcher will launch in the same way as other rockets by lifting off vertically from a launch pad. [25]
When the external solid rocket boosters run out of fuel they will be jettisoned while the rest of Vulcan continues towards space.
After the first stage has run out of fuel, it will separate from stage 2. The engines will also separate
from the tank. The first stage tank will not be reused, only the engines. ULA claim that ‘this will take up 90 percent of the propulsion cost of the booster.” [24]
The engine will then deploy an inflatable heat shield to protect it from re-entry. After slowing down sufficiently, the heat shield is separated. [25]
A parafoil is then deployed from the engines to reduce its terminal velocity further and as it descends a helicopter will catch it mid-flight. [25]
Depending on the launch trajectory, the helicopter will then either deliver the engines back to the launch site or onto a waiting ship. [24]
The engine can then be analysed and serviced before being reused for another launch. [26]

/ULA SMART Reuse – Progress
ULA plan to launch Vulcan for the first time in 2019 but sources say that the reusable technology may not be fielded until as late as 2024. On 17th September 2015, ULA announced that they will pay Blue Origin, a space organisation led by founder of Amazon – Jeff Bezos, to complete development of a new engine to replace the current Russian-made RD-180 engine that powers the first stage of the Atlas 5 rocket. [27] ULA Chief Executive Tory Bruno said the new engine has the potential to substantially reduce launch costs but declined to be specific. [27]
In October 2014, ULA announced a major restructuring of processes and workforce in order to half launch costs. One of the reasons for this was competition from SpaceX [28], a private aerospace business who offer much cheaper launches and are actively working towards making their launchers partially reusable in order to reduce launch costs further. In the market for launch of US military payloads, ULA has faced no competition for nearly a decade since its formation in 2006. The military space launch arrangement in the US has been called a monopoly by space analyst Marco Caceres and criticized by some in the US Congress. [28]

/Adeline – Intro/
In June 2015, Airbus Defence & Space unveiled their re-usable rocket concept named Adeline, standing for Advanced Expendable Launcher with Innovative engine Economy. According to Airbus, this concept could be used on any launcher, however small or large and is likely to be used on the upcoming Ariane 6 launcher.

/Adeline – Demo/
//DEMO VIDEO PLAYING IN BACKGROUND//
The rocket will launch as usual vertically from a launch pad.
If SRBs are used on the launcher then they will be jettisoned after burning all of their fuel.
After the first stage tank has burnt though its fuel it will be jettisoned from the rest of the spacecraft which will carry on its journey to space. ‘Adeline’ will then separate and begin it ballistic re-entry at over 5 times the speed of sound.
As ‘Adeline’ reaches the lower atmosphere it will pull out of its dive and activate its solar powered propellers to power it to the landing strip.
Adeline will then land on a runway like a plane where it can be recovered and prepared for reuse on another flight. The first stage fuel tank will not be reused.
Airbus says Adeline represents 70-80% of the total value of the launch vehicle. [29]

/Adeline – Progress/
Development and testing of Adeline began in 2010. After simulator testing, the first demonstrators were tested, in various conditions, to validate the technical elements ahead of a maiden flight which is scheduled for 2025. [29]
Herve Gilbert, a chief technical officer at Airbus Defence & Space said that Ariane engines could be used perhaps 10-20 times and that Adeline could generate savings of 20-30% for a launch. He went on to say that the extra mass does cause a reduction in performance of the rocket overall but said this was maybe as little as 10%. [30]
Airbus have said they have spent about 30 million euros on its reusable technology programme and are planning on testing even bigger demonstrators. [30]

/Falcon 9/Heavy – Intro/
SpaceX is a private aerospace company in the US founded by Elon Musk, co-founder of PayPal, and CEO of Tesla Motors [31] with the aim “to revolutionize space technology, with the ultimate goal of enabling people to live on other planets.” [32]
SpaceX are currently working towards making their Falcon 9 launcher’s first stage reusable [33] and their upcoming Falcon Heavy will also be partially reusable. [34]
While Falcon 9 has currently only carried unmanned cargo, in the future both Falcon 9 and Falcon Heavy will be capable of launching humans to space in SpaceX’s Dragon capsule. Falcon Heavy will even be capable of taking a small payload to Mars. [34]

/Falcon 9/Heavy – Demo/
//DEMO VIDEO PLAYING IN BACKGROUND//
/Falcon 9/
Falcon 9 will lift off the pad with over 6,800kN of thrust with all 9 of its Merlin engines firing. [33] This is more than five Boeing 747s at full power. [33] With its nine first stage engines clustered together Falcon 9 can also sustain up to two engine shutdowns during flight and still successfully complete its mission. [33]
Approximately 3 minutes after lift-off, the first stage will be separated while the second stage carries the payload to orbit. [35]
The first stage then uses its nitrogen cold gas thrusters to orient itself towards the launch site before re-lighting 3 of its Merlin engines to perform the ‘boost-back’ burn. [35]
When Falcon 9 reaches about 70km in altitude it relights 3 engines again to slow from 1,300 m/s to just 250. This burn lasts about 20 seconds. To protect from the intense heat, Falcon 9 has shielding on the aft section. [35]
The first stage also uses four aerodynamic control surfaces known as grid fins to control its trajectory to ensure it lands at the target area.  Just before impacting the ground, one Merlin engine is fired up to slow the stage down so that it can land safely.  As the stage is very light at this point because most of the fuel has been spent, the stage cannot hover – even one Merlin engine at the lowest possible throttle would be too much. Because of this Falcon 9 must fire its engine at precisely the right time so that its velocity is cancelled out at the moment it touches down. This is often referred to as a hover-slam or suicide burn. [35]
Heavier payloads may require Falcon 9 to land on SpaceX’s Autonomous Spaceport Drone Ship, or ASDS, in the ocean as it will not have enough fuel to go back to the launch site.
/Falcon Heavy/
Falcon Heavy is essentially a Falcon 9 with two extra Falcon 9 first stages attached on the side. As a result of this, its launch and landing systems are very similar, only with three cores instead of one.
Falcon Heavy will launch from the pad into space like Falcon 9 then, when there is only a small amount of fuel left in the two boosters, they will separate and land in the same way as the Falcon 9. They use their cold gas thrusters to orient then boost-back to the landing site. [36]
Falcon Heavy continues onwards until the first stage is low on fuel. It will then separate and land in the same way again. Depending on the payload, the first stage may not have enough fuel to land back at the launch site so will land on the ASDS in the ocean instead. [36]

/Falcon 9/Heavy – Progress/
Testing of SpaceX’s reusable system began in 2012 with their test vehicle ‘Grasshopper’. In its first test on 21st September, Grasshopper had a brief 3 second flight in which it hopped 1.8m. This seems pretty insignificant in its self but was the start of something much bigger. Grasshopper had a total of eight flights over the course of 13 months, each going higher with the exception of flight 7 which demonstrated its ability to divert as it travelled 100m laterally and then returned back to the pad. For its final flight Grasshopper climbed to 744m before descending on 7th October 2013. [37]
Grasshopper’s successor, the ‘Falcon 9 Reusable Development Vehicle’ – or F9R Dev1 – was announced in October 2012, although under the name of ‘Grasshopper v1.1’ until early 2014. F9R Dev1 had 5 flights and climbed to 1,000m before landing. Flight 3 included the steerable grid fins that are on the current Falcon 9. On its 5th flight on 22nd August 2014 the vehicle self-destructed as it detected a flight anomaly that began to take F9R Dev1 off of its planned flight path. A blocked sensor caused the anomaly and there was no backup sensor on the prototype vehicle although the flight version of Falcon 9 has a redundant backup. [37] There were no injuries as a result of the anomaly. [37]
SpaceX also began testing the landing capabilities of full Falcon 9s. On several payload launches, after the first stage separated from the rest of the rocket, they tested soft landing the stage in the ocean, as if there were something for it to land on. [38] The first test was of the 6th Falcon 9 launch on 29th September 2013. The stage successfully reoriented, reignited three of its Merlin engines and successfully performed the first burn and re-entered the atmosphere safely. The stage began to roll because of aerodynamic forces however which caused the fuel to ‘centrifuge’ and the single engine involved with the deceleration burn shut down. [38] The 9th flight of Falcon 9 on 18th April 2014 was the second soft landing attempt and was successful. The 10th flight successfully landed the stage in the ocean with the legs deployed and much closer to the coast to simulate a more realistic landing. [38]
The 14th flight of Falcon 9 involved the first attempt at landing on the Autonomous Spaceport Drone Ship (ASDS). The first stage successfully performed the boost-back and re-entry burns however hit the drone ship hard and exploded, the ship itself was mostly undamaged. SpaceX CEO Elon Musk later elaborated that the flight control surfaces had exhausted their supply of hydraulic fluid prior to the impact. [38]
Another ASDS landing was attempted on 14th April 2015 with Flight 17. This time the stage landed on the ship but due to excess horizontal velocity it didn’t settle and exploded upon tipping over. Elon Musk later clarified that a valve was stuck so the system could not react rapidly enough for a successful landing. [38]
Following a several month break after a failed Falcon 9 launch, SpaceX attempted to land the next Falcon 9 stage on land back at the launch site. The landing succeeded when the stage touched down approximately 9 minutes and 45 seconds after launch on 21st December (local time). Although recovered the stage will not be used again in another launch. Instead SpaceX have been running several tests on the stage. On 31st December 2015, SpaceX announced that no damage had been found and it was ready to perform a static fire test, which was conducted on 15th January 2016. The test was reported good overall but one of the outer engines, “engine 9” showed thrust fluctuations. Musk reported that this may have been due to debris ingestion. [38]
Another landing was attempted on the ASDS again on 17th January 2016. The rocket successfully completed all burns and landed on the ship however one of the 4 landing legs did not lock so folded back up after landing which caused the stage to tip over and explode. Elon Musk said that the cause could have been ice build-up due to fog at launch. [38]
The latest landing attempt was on the 4th March which was unsuccessful though due to the nature of the mission, a successful landing was not expected.
Falcon Heavy is currently planned to have its demonstration flight in November 2016 where it will attempt to land all 3 of its first stage cores.

/Outro & Summary/
Over the coming years we may see many of these concepts progress into a reality. This will massively reduce launch costs, accelerating our ability to explore space and learn more about what’s out there. Reusable launch vehicles doesn’t just save money though – they also reduce wasted materials which is becoming more of a concern every day.

Sources
[1] https://en.wikipedia.org/wiki/List_of_V-2_test_launches
[2] https://en.wikipedia.org/wiki/Space_exploration#First_flights
[3] https://en.wikipedia.org/wiki/Ariel_1
[4] https://en.wikipedia.org/wiki/Yuri_Gagarin
[5] https://en.wikipedia.org/wiki/Low_Earth_orbit
[6] https://en.wikipedia.org/wiki/Saturn_V
[7] https://en.wikipedia.org/wiki/Apollo_11
[8] https://en.wikipedia.org/wiki/Space_Shuttle_program
[9] https://en.wikipedia.org/wiki/Falcon_9
[10] https://en.wikipedia.org/wiki/Falcon_Heavy
[11] https://en.wikipedia.org/wiki/Kármán_line
[12] https://en.wikipedia.org/wiki/Space_Shuttle_orbiter
[13] https://en.wikipedia.org/wiki/Space_Shuttle
[14] https://en.wikipedia.org/wiki/Boeing_747-400#Specifications
[15] https://en.wikipedia.org/wiki/Space_Shuttle_Orbital_Maneuvering_System
[16] https://en.wikipedia.org/wiki/Hubble_Space_Telescope
[17] https://en.wikipedia.org/wiki/List_of_Space_Shuttle_missions
[18] https://en.wikipedia.org/wiki/Space_Shuttle_Columbia_disaster
[19] https://en.wikipedia.org/wiki/Criticism_of_the_Space_Shuttle_program
[20] http://spacenews.com/startup-spotlight-swiss-space-systems-s3/
[21] https://en.wikipedia.org/wiki/SOAR_(spaceplane)
[22] http://www.parabolicarc.com/2015/12/20/s3-postpones-flights-ipo-financial-trouble/
[23] https://en.wikipedia.org/wiki/United_Launch_Alliance
[24] http://spaceflightnow.com/2015/04/14/ula-chief-explains-reusability-and-innovation-of-new-rocket/
[25] https://www.youtube.com/watch?v=lftGq6QVFFI
[26] http://www.defensenews.com/story/defense/air-space/space/2015/04/13/ula-unveils-reusable-vulcan-launch-vehicle/25737327/
[27] http://spacenews.com/41901ula-to-invest-in-blue-origin-engine-as-rd-180-replacement/
[28] https://en.wikipedia.org/wiki/Space_launch_market_competition
[29] https://airbusdefenceandspace.com/reuse-launchers/
[30] http://www.bbc.co.uk/news/science-environment-33006056
[31] https://en.wikipedia.org/wiki/SpaceX
[32] http://www.spacex.com/about
[33] http://www.spacex.com/falcon9
[34] http://www.spacex.com/falcon-heavy
[35] http://spaceflight101.com/spacerockets/falcon-9-v1-1-f9r/
[36] http://spaceflight101.com/spacerockets/falcon-heavy/
[37] https://en.wikipedia.org/wiki/Grasshopper_(rocket)
[38] https://en.wikipedia.org/wiki/Falcon_9_booster_landing_tests