What was once thought to be a pipe dream of having a reusable system of rocket and rocket components to reduce the overall cost of spaceflight is now gaining significant traction, as SpaceX leads the way toward a fully reusable first stage, while the United Launch Alliance and the European Space Agency move toward reusability to compete in the ever-changing launch market.
History of reusability:
The concept of reusability in the launch arena has been discussed since spaceflight operations began in earnest in the 1950s and 60s.
Gaining major prominence in the 1970s when the Space Shuttle program was approved by the United States Congress, the concept of reusing rocket components to reduce the overall cost of spaceflight entered the main public arena.
Original plans for the Shuttle included the reusability of all major components of the system, including the Orbiter, twin Solid Rocket Boosters, and the External Tank.
Eventually, the design was simplified so that the Orbiter and the Solid Rocket Boosters were the only reusable components of the vehicle.
However, the total cost savings for reusability never materialized for the entirety of the program.
Now, with the new safety requirements for the successor vehicle to the Shuttle, the Space Launch System rocket, and the elimination of the need to recover the SRBs for post-flight safety inspection, NASA will not reuse the SRBs after each flight of the SLS – opting instead to simply build new casing segments for each SRB from scratch for each mission.
Thus, NASA is returning to the model of expendability for its launch components, a modus operandi that the world’s launch services have operated under for decades.
SpaceX: The next step forward
But for Elon Musk and SpaceX, giving up on the idea to create a cost-effective reusable system to reduce expenses and increase safety was simply not acceptable.
Originally, the goal was to have the first and upper stages of the Falcon 9 rocket return to Earth under their own power for post-flight inspection, refurbishment, and reuse on future missions.
That was quickly refined to a primary desire to reuse the Falcon 9’s first stage, thereby recovering all nine of the Merlin engines (as well as the entire first stage) for reuse on future flights.
To make this desire a reality, SpaceX conducted a series of scaled tests at the company’s test site in McGregor, Texas as well as in-flight tests during the CASSIOPE and Thaicom-6 satellite launches.
All of these tests allowed SpaceX to refine their approach toward the ultimate test of successfully landing the first stage of the Falcon 9 on a floating barge in the middle of the Atlantic Ocean.
The first test of this objective occurred during the CRS-3/SpX-3 Dragon mission to the ISS.
During this test, the first stage of the Falcon 9, equipped with landing legs, touched down in the Atlantic Ocean to demonstrate the stage’s ability to make a soft, vertical and controlled landing.
While the stage was quickly swallowed by the high seas, the objectives of the flight were met, with SpaceX gaining the understanding that the core stage needed grid fins for increased stability.
This new landing system debuted on the CRS-5/SpX-5 mission, with the goal being to land the first stage on the Autonomous Spaceport Drone Ship (ASDS), nicknamed Just Read The Instructions.
The landing, by all accounts, came much closer to success than anyone could have predicted, with the stage finding the deck, but at an angle, before tumbling over the side of the drone ship into the ocean.
SpaceX increased the hydraulic fluid supply before the next landing attempt following the successful completion of the first stage’s role as part of lofting the Deep Space Climate Observatory (DSCOVR) spacecraft into orbit.
Poor sea conditions impacted on the ASDS’s role of being in position to receive the stage, resulting in SpaceX opting to call off the landing attempt, instead allowing the stage to conduct a soft landing in the ocean.
Nonetheless, the soft water landing showed that the stage returned through its re-entry and landing burns with good stability.
It was later noted that the landing was stable and precise – and may have resulted in a good landing had the ASDS been able to receive it.
These improvements paved the way for the next attempt to land the first stage on the ASDS during the CRS-6 mission of Dragon on a cargo run to the ISS – a landing attempt that came even closer to success than the first barge landing attempt on CRS-5.
During the CRS-6 landing attempt, the first stage successfully found the ASDS barge and performed a soft landing with just a bit too much lateral velocity.
As both up-close and long-range tracking video of the landing attempt released by SpaceX showed, thrusters at the top of the stage tried to mitigate the lateral movement, but the stage eventually lost its fight with gravity and tipped over – resulting in the destruction of the first stage but a very close to successful landing attempt.
With the probability of a successful landing now thought to be quite high, the historic milestone of a Falcon 9 first stage landing on the deck of the ASDS would initiate an additional test program.
This new test program would result in the recovered stage being safed and shipped to Spaceport America in New Mexico where it would then undergo a series of tests to identify hardware limits, such as how many cryo-cycles the stage can withstand.
Provided continued success of first stage recovery efforts, it is currently believed that the second recovered first stage would subsequently take on the qualification testing role, an effort that will hopefully lead to the first launch of a reused first stage in late 2016.
However, SpaceX does not intend to permanently recover the Falcon 9 first stages via the use of the ASDS landing barge in the Atlantic Ocean.
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That barge is in fact part of the long-range goal of proving to the United States Air Force (USAF) and the Federal Aviation Administration (FAA) that successful pinpoint landings can be achieved in routine fashion – thus leading to the first ever permit from the USAF and the FAA to return the first stage directly to land.
Currently, it is understood that SpaceX will try again to land the first stage of the Falcon 9 on the ASDS during this weekend’s CRS-7 mission of Dragon to the ISS.
Assuming that this landing attempt is successful, it is understood that SpaceX will then proceed with plans to return a Falcon 9 first stage directly to land during the Jason-3 mission launch from Vandenberg Air Force Base in California.
However, whether the Jason-3 mission Falcon 9 first stage returns to land or to an ASDS is at the mercy of SpaceX’s confidence levels and the pending results of the CRS-7 landing attempt.
If a barge landing is opted for instead of a direct return to land, a new ASDS, based on the West Coast, will be ready to receive the Jason 3’s Falcon 9 first stage in the Pacific Ocean.
Regardless of Jason 3, returning the first stages directly to land is important to SpaceX as these advances will feed into SpaceX’s Falcon Heavy rocket, which will be aiming to return three cores per mission.
It has been argued that returning all three cores from Falcon Heavy flights could result in that variant of the Falcon 9 becoming cheaper to operate than an expendable Falcon 9.
However, the exact nature of the reduction in costs for Falcon 9 launches provided by the return and reuse of the first stages remains to be seen or realized.
United Launch Alliance: Enter the Vulcan
But that has not stopped other launch competitors in the expendable launch vehicle arena from quickly changing their tune about the nature of reusability.
Forming the backbone of the US launch campaigns are the Atlas V and Delta IV rockets.
While both of these rockets have impeccable safety records – with the Atlas V actually boasting a 100 percent success rate as deemed by its users – both vehicles share one thing in common: None of their components are reusable.
And in fact, reusability of these vehicles was never earnestly looked into by the companies that manage them, with United Launch Alliance (ULA) – which now operates the Atlas V and Delta IV vehicles for the United States – even rebuking ideas of reusability when SpaceX stated it as one of their goals.
But with the increasing probability of success in the recovery and reusability efforts of SpaceX, and SpaceX’s ability to already offer competitive launch services to the Atlas V and Delta IV vehicles with a similar performance margin and so far the same safety margins, ULA has changed its tune regarding reusability.
So much has ULA’s position changed that the company is in fact now looking into a complete vehicle system replacement for its fleet of Atlas V and Delta IV rockets.
At the core of this strategy is the company’s new Vulcan rocket.
Due in part to geopolitical and US political considerations regarding Russian built engines for the Atlas V fleet and also to increasing competition from SpaceX, ULA announced in September 2014 that it had entered into partnership with Blue Origin to develop a new series of liquid oxygen and methane engines for a new first stage booster.
This announcement was followed one month later by ULA’s restructuring of the company and workforce to reduce launch costs by half due to increasing competition in the launch market from SpaceX.
It was also during this announcement that the company unveiled plans to blend its existing Atlas and Delta technologies to build a successor for the Atlas V rocket – again, with the principal goal being to cut launch costs in half.
At the time, this successor was simply referred to as a next generation launch system.
It was not until April 2015 that ULA officially unveiled the launch vehicle as Vulcan.
As of publication, Vulcan has not officially been approved by ULA’s board, but its initial launch is planned for no earlier than 2019 under an incremental approach to introducing the vehicle and its technologies to the launch market.
While the various components of the rocket do indeed blend the Atlas V and Delta IV technologies, at the heart of the new design is the reusability of the first stage core engines.
A significant focus during the rocket’s introduction in April was the plan to allow the engine compartment of the first stage to detach after use.
The engine compartment would then re-enter Earth’s atmosphere, protected by a heat shield, before descending by parachute toward the ocean and being captured by a helicopter before impacting the water.
This type of recovery and reuse has been termed by ULA as SMART, or Sensible, Modular, Autonomous Return Technology.
ULA claims that SMART would allow for a first stage propulsion cost reduction by 90 percent.
However, exactly how much this SMART system would save in terms of the total price to customers for the Vulcan rocket remains to be seen.
It is hoped that this approach would allow for a “bare bones” Vulcan rocket cost of approximately $82 million (U.S.) – roughly half the cost of a basic Atlas V.
In an exclusive Q&A with NASASpaceflight.com, Dr. George Sowers, Vice President of Advanced Concepts and Technologies for ULA stated that one of the biggest challenges for reusing components of rocketry is the business case.
Since no company or agency has yet been able to bring the overall cost of recovery and refurbishment low enough to save money via reuse instead of building anew each time, Dr. Sowers said that he believed ULA’s approach could give his company the best chance of doing so.
However, while ULA has certainly changed its tune regarding the potential for recovery and reuse, the company does not plan to institute its SMART program in the early stages of Vulcan’s introduction to the launch market.
In fact, according to Dr. Sowers, ULA is expected to phase in its SMART recovery system gradually.
“The first step is to mature the HIAD (hypersonic inflatable aerodynamic decelerator) technology. We are working with NASA on that. We [then] plan to start with engine recovery and see where that leads,” said Dr. Sowers.
Furthermore, ULA will likely take a scaled approach toward the introduction of the SMART recovery plans via a series of sub-scale demonstrations leading to a series of full-scale flight experiment.
In terms of what this means for the overall launch market and the potential to increase the overall annual launch frequency, Dr. Sowers said that only time will tell.
“Increasing launch rate means increasing launch sales which means getting new customers. That can happen in two ways: take customers away from someone else (via lower prices) or generate new demand. We all hope for the latter.”
In terms of SpaceX’s demonstrations for landing and recovering the first stage of their Falcon 9 rocket, Dr. Sowers was optimistic that SpaceX would be fruitful in this endeavour.
However, he cautioned that “even if (SpaceX) successfully demonstrates that technical capability, which I believe they will, I don’t believe the business case closes. In other words, I don’t think the economics of launch (measured in dollars/kg to orbit) will be improved relative to the equivalent expendable vehicle.
“Our approach to reuse does lead to improved dollars/kg.”
In other words, ULA believes that its approach to recovering only the propulsion system of the first stage instead of the entirety of the first stage is the key toward making a strong and viable business case for recovery and refurbishment.
Adeline: A reusable system for Europe’s Ariane rocket
But the increasing competition in the United States to produce rocket delivery systems that both lower the cost to customers while maintaining the same level of safety now expected within the industry has had implications stretching outside the borders of the United States.
For it is not just U.S. markets that the U.S. launchers compete in.
In fact, the entirety of the world’s spaceflight groups compete with each other for civilian and governmental launches from nations that do not have their own space programs or for whom it is cheaper to simply contract launch services than provide it themselves.
Thus, with the U.S. markets now moving toward reusability and a sharp reduction in costs, the European Space Agency (ESA) has begun focusing part of its attention on a move toward reusability and a reduction in its overall launch systems costs to maintain the Ariane 5’s (and successor Ariane 6’s) viability in the industry.
To this end, ESA is already pursuing the development of the Ariane 6 launch vehicle as a replacement for the Ariane 5 in the 2020s.
Under the current configuration, no components of the Ariane 6 will be reusable.
But that does not mean that components could not be reconfigured for recovery and reuse.
In this way, Airbus, which leads the production of ESA’s Ariane 5 rocket, has put forward a concept for a partially reusable system codenamed Adeline (ADvanced Expendable Launch with INnovative engine Economy).
Under this system, which Airbus believes could easily be incorporated into the Ariane 6’s design between 2025 and 2030, the Ariane 6’s first stage engines and avionics packages would detach from the first stage after use, re-enter Earth’s atmosphere, and then fly itself back to a runway at or near the Guiana Space Centre in Kourou, French Guiana.
Airbus currently believes that this type of reuse system could help offset 20 percent to 30 percent of the total cost of a flight and could result in the engines and avionics packages being re-flown between 10 to 20 times.
However, unlike ULA, which announced its reuse plan in response to SpaceX, Airbus has taken a different route.
While not announced until June 2015, Airbus has in fact been working on this Adeline model since 2010, and has even carried out a series of small scale tests to determine the viability of an autonomous flyback system for the engines and avionics compartment.
Moreover, while ULA’s approach is specific to the development of the Vulcan rocket, Airbus’s approach would be compatible with any liquid fueled first stage rocket, not just the potentially forthcoming Ariane 6 variant.
Looking forward:
Regardless of what approach is taken, the fact that the world’s leading space launch companies in the Western Hemisphere are all turning their attention toward reusability for the purpose of reducing costs is a positive step.
While these companies will have to avoid creating a system so complex that its refurbishment costs offset the potential cost savings of recovery and reuse, all this will mean nothing if safety is compromised in the process.
Part of building a business case for recovery and reuse is maintaining the level of confidence that customers have in the safety and reliability of the rocket system.
And this will mean a transition in how the industry thinks about its systems and how customers view those systems as well.
Essentially, reusing key components of a vehicle, be it an entire first stage or just the engine core and avionics systems, means that users will be relying on “second hand” systems – ones that have been used at least once prior.
But if safety margins can be maintained and costs can be reduced, even just slightly, then the potential for opening the launch market to customers who previously have not been able to afford the cost of the launcher would be improved.
(Images: via L2’s SpaceX Section, including renderings created by L2 Artist Nathan Koga – Click here for full resolution F9, F9-R, FH and BFR renderings and more – these are not official SpaceX images. Other images from SpaceX, Airbus and ULA)
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