The history of reusable launch systems

For this new article on Space Legal Issues, let’s have a look at the history of reusable launch systems. With the invention of rocket propulsion in the first half of the twentieth century, space travel in the void beyond the atmosphere became a technical possibility. The subject of reusable launch systems presents a certain industrial sensitivity. In a context of economic competition between space launchers, especially between Ariane (Europe) and SpaceX (USA), it is interesting to propose a historical synthesis of reusable launch systems projects developed in the past decades. “If one can figure out how to effectively reuse rockets just like airplanes, the cost of access to space will be reduced by as much as a factor of a hundred. A fully reusable vehicle has never been done before. That really is the fundamental breakthrough needed to revolutionize access to space” – Elon Musk.

The last decade of the second millennium saw the emergence of the idea of sending payloads into space with reusable launch vehicles (RLVs). It appeared to make economic sense to reuse a launch vehicle that cost as much as a small airliner, rather than throw that vehicle away after one use. In the following of the post-war epoch cosmonautics was experiencing a rapid development that resulted in a piloted space flight and a landing on the Moon in 1969. Reusable launch systems became a major subject of development in the early 1970s. This epoch also gave rise to the largest project in the field of reusable space vehicles. It was the STS Space Shuttle program, which was the first reusable space vehicle to be operational. At present these space shuttles have already been retired from service for technical and economic reasons.

Launch Systems

Before looking at the history of reusable launch systems, let’s have a look at some definitions. An expendable launch system (ELS, or expendable launch vehicle, ELV) is a launch system or launch vehicle stage that is used only once to carry a payload into space. Historically, satellites and human spacecraft were launched mainly using expendable launchers. ELV advantages include cost savings through mass production, and a greater payload fraction. Their components are not recovered. This contrasts with a reusable launch system or RLV, in which some or all of the components are recovered intact. The vehicle typically consists of several rocket stages, discarded one by one as the vehicle gains altitude and speed. A few companies are developing reusable launch systems intended to cut costs. A reusable launch vehicle, such as the SpaceX Falcon 9 first-stage booster, may be flown in “expendable configuration” to increase performance, although this is unusual. The now-retired Space Shuttle was one of the earliest RLVs. It was intended to greatly reduce launch costs, but actually increased them.

A reusable launch system (RLS, or reusable launch vehicle, RLV) is a space launch system intended to allow for recovery of all or part of the system for later reuse. To date, several fully reusable sub-orbital systems and partially reusable orbital systems have been flown. However the design issues are extremely challenging and no fully reusable orbital launch system has yet been demonstrated. A wide variety of system concepts have been proposed, and several are represented in those which have actually flown. The first aircraft to attain sub-orbital flight was the North American X-15. The first reusable vehicle to reach orbit was NASA’s Space Shuttle. It was intended to reduce launch costs below those of expendable launch systems, but instead ended up being more expensive. The last Shuttle was retired in 2011.

During the 21st century, commercial interest in reusable launch systems has grown. The SpaceX Falcon 9 rocket has a reusable first stage and expendable second stage, and is currently in use for the NASA Commercial Orbital Transportation Services program and commercial satellite launches. Additionally, SpaceX is developing the fully reusable BFR for manned interplanetary missions. Scaled Composites have flown two prototype sub-orbital spaceplanes for Virgin Galactic, while the Blue Origin New Shepard rocket has recoverable first stages and capsules but is only capable of suborbital flights.

The history of reusable launch systems

Almost all operational space launchers are now expendable launchers, that is to say, which serve only once. In an era marked by global overcapacity of launch, launch cost and reliability play a key role in the competition between launchers. The idea of making multi-stage launchers was born at the beginning of the twentieth century, thanks to Konstantin Tsiolkovsky, and the pioneers of astronautics realised early the great technological difficulty to achieve a single-stage Earth orbitation (SSTO for Single Stage To Orbit) and that the two stages (TSTO for Two Stages To Orbit) was more accessible. However, there have been many SSTO projects, some of them reusable; none has yet emerged.

A short definition of reusable launch systems can be: a launcher, which is responsible for putting a payload into Earth orbit, civil or military, where one of the major building blocks can be retrieved and reused. This element may be a first stage or part thereof or the upper stage. The best-known example of a partially reusable launcher is the American Space Shuttle. The Space Shuttle was a partially reusable low Earth orbital spacecraft system operated by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. The two solid propellant propellants (SRMs) were parachuted and rearranged by Thiokol, now Northrop Grumman Innovation Systems, while the Space Shuttle itself was capable of returning from orbit by its own means, to land and fly later (Columbia, Challenger, Discovery, Atlantis, and Endeavour). The demonstration of recovery/reuse was successful but at a cost such that this technology was abandoned in 2011, in favour of a return to consumable launchers.

Why are we talking again about reusable launch systems? Today, in a very competitive environment, it is important to significantly reduce the launch cost, to increase the availability of launchers and to develop new applications or new capabilities. Recent breakthroughs by SpaceX and Blue Origin have boosted momentum. Some launchers targeting space tourism are inherently recoverable and reusable, they constitute a sector of activity which is really interesting.

Looking at the history of reusable launch systems, past concepts, of which very few have given rise to demonstrations, much less to operational systems, can be schematically categorised as those for the recovery/reuse of the upper stage and those for the recovery/reuse of the lower stages. A number of these projects have used a rail acceleration device, such as Eugen Sänger’s Silbervogel and the work of Irene Sänger-Bredt. These military projects have not been realised and it may be thought that the infrastructure to be developed on the ground had certain limitations for the planned missions.

Most reusable upper stages are of the “orbital spaceplane” type. These are winged vehicles capable of “landing” from an orbit to return to Earth, land there or be parachuted. The vehicles must therefore have real aerodynamic qualities in the hypersonic, supersonic, transonic and subsonic domains. They can be used as means of orbiting a payload or for other types of military or civilian missions.

The Crew Return Vehicle (CRV), sometimes referred to as the Assured Crew Return Vehicle (ACRV), was a proposed dedicated lifeboat or escape module for the International Space Station (ISS). A number of different vehicles and designs were considered over two decades – with several flying as developmental test prototypes – but none became operational. Since the arrival of the first permanent crew to the ISS in 2000, the emergency return capability has been fulfilled by Soyuz spacecraft rotated every six months.

Let’s also mention the Boeing X-20 Dyna-Soar, a United States Air Force (USAF) program to develop a spaceplane that could be used for a variety of military missions, including aerial reconnaissance, bombing, space rescue, satellite maintenance, and as a space interceptor to sabotage enemy satellites. The program ran from October 24, 1957 to December 10, 1963, and was cancelled just after spacecraft construction had begun. Other spacecraft under development at the time, such as Mercury or Vostok, were based on space capsules that returned on ballistic re-entry profiles. Dyna-Soar was more like the much later Space Shuttle. It could not only travel to distant targets at the speed of an intercontinental ballistic missile, it was designed to glide to Earth like an aircraft under control of a pilot. It could land at an airfield, rather than simply falling to Earth and landing with a parachute. Dyna-Soar could also reach Earth orbit, like Mercury or Gemini. These characteristics made Dyna-Soar a far more advanced concept than other human spaceflight missions of the period. Research into a spaceplane was realised much later, in other reusable spacecraft such as the Space Shuttle (which had its first orbital flight in 1981).

In the history of reusable launch systems, there was also Hermes, a proposed spaceplane designed by the French Centre national d’études spatiales (CNES) in 1975, and later by the European Space Agency (ESA). It was superficially similar to the American Boeing X-20 Dyna-Soar and the larger Space Shuttle. In January 1985, France proposed to proceed with Hermes development under the auspices of the ESA. Hermes was to have been part of a manned space flight program. It would have been launched using an Ariane 5 launch vehicle. In November 1987, the project was approved; it was to commence an initial pre-development phase from 1988 to 1990, after which the authorisation to proceed to full-rate development was to depend on the outcome of this phase. However, the project was subject to numerous delays and funding issues around this period. In 1992, Hermes was cancelled. This was in part due to unachievable cost and performance goals, as well as the formation of a partnership with the Russian Aviation and Space Agency (RKA), which reduced the demand for an independent manned spaceplane. As a result, no Hermes shuttles were ever built. During the 2010s, it was proposed to relaunch the Hermes vehicle to serve as a partially reusable air-launched spaceplane launch system, known as SOAR.

Finally, let’s mention Saenger or Sänger, a West German concept design for a two-stage-to-orbit spaceplane. It is named after Eugen Sänger, who had been a key figure in the development of the concept for aerospace company Junkers. Its first incarnation, designated as Saenger I, started developed during the 1960s. During the 1980s, the German government took increasing interest in the project for use as a reusable launch system, resulting in the project gaining official support and work commencing on an enlarged version of the vehicle, known as Saenger II. Work on the project was terminated during 1995 as consequence of the high projected costs of proceeding and perceived limited performance gains in comparison to existing expendable launch systems such as the Ariane 5 rocket.

The reuse of the lower stage has given rise to a wide variety of formulas: to deliver a large take-off thrust, solid propellant engines are used in several countries. The reuse of this type of engine was performed on the American Space Shuttle, it was considered on Ariane 5 and abandoned; in fact, the parachute recovery is done at sea, which imposes a rather heavy logistics system and finally the economic interest is not reached. The launch can be airborne, that is to say that the first stage is a piloted aircraft or automatic; this flexible enough formula certainly has a future for launching small satellites; there have also been many launchers projects using an aerobic powered first stage.

The recovery of a first stage equipped with liquid propellant can be economically attractive because the cost of these engines is high and their original design can provide for reuse; several technologies have been imagined: by parachute, by rotor, return of boosters using wings and aerobic engines, vertical powered return, by recovering only a few critical parts including the engines… The concepts on which research and development are based today are as follows: achievements and demonstrations in progress with SpaceX, which has managed several recoveries of the first stage of the Falcon 9, either on barge at sea or on land near the launch site (reuse of a first stage is planned in the coming months). Blue Origin has also achieved several vertical returns from its New Sheppard for space tourism.

Looking at the history of reusable launch systems, we can conclude by saying that until today, reusable launchers have encountered many difficulties, mainly related to operations and regulatory aspects, particularly for security. Reuse inexorably induces a loss of performance compared to consumable launchers, and if we examine the problem from the sole economic point of view, by using the cost of the kilogram put into orbit, the result for reuse is not at the rendezvous. Let’s try to detail these different problems. In the first place, it should be remembered that the solutions to be implemented depend on the mission profiles concerned. There is therefore no general optimal solution.