NASA’s Space Shuttles have become a familar sight in their thirty years of service, but there have been other shuttle designs which never left the ground.Some were ingenious alternative concepts to the vehicle which is shortly to be retired, some were potential replacements and there was even a couple of foreign competitors.Let us examine some of the space shuttles that never were.
Back in the mid-1960s planners at NASA saw a rosy future of ever-expanding manned space exploration. Obviously, soon Earth orbit would fill up with space stations staffed by scores of astronauts, meanwhile giant interplanetary space vehicles would be assembled in orbit before setting off to conquer Mars and beyond. Sober space technocrats envisaged that there would soon be a need to launch hundreds of tonnes of cargo and dozens of people into space every month. This could easily be done with expendable rockets but would be horribly expensive considering how much precision-made hardware would be discarded with every launch (how would airlines function if jet airliners were thrown away after a single flight?) To answer this need the concept of a space shuttle was born. A shuttle would be a reusable spacecraft designed to blast off, deliver a payload into orbit and quickly return to Earth. After landing, the craft would be serviced, refueled and reloaded for another mission in a few days at most. A shuttle would operate as smoothly and reliably as a commercial airliner.
Lockheed Starclipper (1968)
Anticipating a possible lucrative contract to build dozens of shuttles, the giants of US aerospace began to sketch out designs. A typical concept from this era was the elegant Lockheed Starclipper. Compared to today’s 122ft long Shuttle Orbiter, this would have been a big vehicle (186 ft long), launched vertically with a V-shaped expendable propellant tank wrapped around it.During the ascent this empty tank would have been discarded like the External Tank of today’s Shuttle. A cargo bay could accommodate payloads up to 60 ft in length and 22 ft wide. After enduring the heat of re-entry, a Starclipper would deploy a set of jet engines and a pair of fold-out wings (not shown in the picture) and fly (rather than glide) to a runway landing. (Source:Frontiers of Space by Philip Bono and Kenneth W. Gatland, Blandford, 1969, Aerospace Projects Review Vol3 No.2)
In 1968, NASA officially declared a goal of developing a space shuttle (or Space Transportation System) and Lockheed submitted a design based on the Starclipper to the first stage, Phase A, of this project. Most of the designs put forward were two stage spaceplanes, pairs of aeroplane-like vehicles which would be launched vertically. One of the duo acted as a booster, carrying its partner to high speed and high altitude then they would separate. The booster would return to land on a runway while the other spaceplane travelled on to orbit.
Not all Shuttle contenders were multi-stage spaceplanes.The Single-stage Earth Orbital Reusable Vehicle (SERV) looked like a grossly enlarged Apollo Command Module which would take-off and land vertically. At launch it would rise majestically pushed by the thrust of a single huge aerospike engine, after its mission it would re-enter the atmosphere and make a stately, albeit noisy, final descent supported by 40 small jet engines. This behemoth was designed by the engineers of the Chrysler Corporation which may seem surprising, but Chrysler was once a big player in the space industry, being the builder of both the Redstone booster which lobbed Alan Shepard and Gus Grissom into space and the first stage of the Saturn 1.
Unlike other possible Shuttles, the SERV would usually be launched without a crew but when necessary a small spaceplane called a MURP (Manned Upper-stage Reusable Payload, a proposed McDonnell Douglas product) could be mounted on the tip of the giant booster to carry a crew then return to Earth separately. In theory, a SERV could place about 51 tonnes of payload in LEO (although this would be considerably reduced when the MURP was installed). This unconventional vehicle was studied intensely by Chrysler, but NASA showed little interest and work on it ended in 1971. (SOURCE: Aerospace Projects Review May-June 2003)
Phase B Shuttles (1970)
Phase B of the Space Shuttle development process was an investigation of a variety of two-stage vehicles. Hundred of configurations were studied on paper, computer simulations and as models in wind-tunnels. The pair illustrated above is typical, an Orbiter designed by North American Aviation (manufacturers of the Apollo CSM) mounted on a 12-engined booster designed by General Dynamics. Both are bulky craft full of liquid hydrogen and oxygen propellants with jet engines to fly them back to base. This is exactly what NASA wanted (and when I was a kid, this was what the Shuttle was going to look like).
As the booster was meant to fly home again, there would be no spent rocket stages falling to Earth. Launching the Shuttle over the ocean was not essential and land-locked launch sites could be used as an alternative to the Kennedy Space Center (McConnell AFB in Kansas, about as far from the ocean as you could imagine, was one suggestion).
To justify the need for the Shuttle project, NASA claimed that in the next couple of decades, so many payloads needed to be launched into space, that up to 75 shuttle flights per year would be made.It was expected to be ready by 1977 (no comment). By then reality had intervened. A belt-tightening US Congress was unwilling to fund the project. To carry on with the Shuttle project, NASA needed the support of the US Air Force who wanted a similar craft to launch spy satellites.To bring the USAF on board the project, the Orbiter had to be redesigned.
Two crucial elements demanded by the Pentagon were an expanded cargo bay sized for their largest KH series satellites (this meant the whole vehicle had to grow in size) and delta (triangular) wings. The delta wing was judged vital for the Air Force as it would allow a Shuttle to be launched, deploy a satellite in the course of a single orbit and immediately re-enter the atmosphere to land somewhere in the US. A combination of aerodynamics and orbital mechanics made this feat impossible with the small straight wings favored by NASA. Of course, despite the Shuttle being designed around this mission profile, no Shuttle was never called on to fly it. This whole redesign to military requirements was expensive and ultimately wasted but without it the Shuttle would never have flown.
Phase B Prime designs (1970)
The image above is basically a re-iteration of the Rockwell-GD design to meet the NASA/USAF requirements. At this time things became worse still for NASA, further budget cuts meant there would be no space station to shuttle to. There probably would be a station eventually (1980 perhaps) but for some years the Shuttle Orbiter would have to act as a space station in its own right, staying in space for up a fortnight.The Orbiter would need to be more complex as a result. Then it was realised that designing and building these complicated two-stage craft was impossible with the available funding. A re-think did away with the piloted winged booster, replacing it with two reusable solid fuel boosters. The Orbiter was slimmed down by removing the vast majority of its fuel tankage, moving the propellant to a large throwaway tank.
The Shuttle by now was meant to make fortnightly missions to deliver cargoes of up to 30 tonnes into orbit (in reality, this payload weight was never achieved and this flight schedule was never needed). The jet engines were deleted, instead the Shuttle would make an unpowered gliding descent. This was Phase C of the development, and marks when the Space Shuttle as we know it today was born and North American Aviation (which changed its name to Rockwell International about this time) was chosen to build it.
(In retrospect the decision to make the Shuttle only semi-reusable by eliminating the winged booster was probably wise. Building the Orbiter was a stressful enough process and it is hard for me to see how simultaneously creating another vehicle larger than today’s enormous A380 but capable of reaching 7000 mph (11250 km/h) could have gone smoothly. Scott Lowther at the Up-ship blog agrees (and he really is a rocket scientist!). Separating the two craft at high speed for the first time could have ended in disaster, see the sorry history of the M21/D21 combination for how badly things could have gone wrong. )
The Shuttle design we know today was falling into place, but one engineer had a really, really different idea!
The Rockwell “Breadbox” (1972)
By a long way the most bizarre vehicle in this collection, the Rockwell C-1057 design congealed into existence during the Phase B studies as the result of a request that the Shuttle Orbiter be made as short as possible without sacrificing any payload space. Rockwell engineer Harry Scott’s stunningly imaginative (and I would venture to suggest rather tongue-in-cheek) solution was to turn the cargo bay sideways! The short, squat and very broad vehicle which resulted was nicknamed the “Breadbox” yet allegedly it was aerodynamically sound.How it was to be combined with the ET and SRBs is unknown to me.It is unsurprising that nothing became of this oddball concept.(SOURCE:http://www.secretprojects.co.uk/forum/index.php/topic,1928.0.html )
Shuttle C (1989)
The Shuttle can carry up to 24 tonnes to LEO, yet it is a rather inefficient launch vehicle.It is powerful but every mission ‘wastes’ possible payload weight in the form of the craft’s wings, tailfin, thermal protection system, landing gear and crew compartment.If we ever needed a really big space station in orbit or to launch a mission to Mars, the Shuttle doesn’t cut the mustard.Various ideas to maximise the Shuttle’s payload by deleting everything not essential have been considered.Shuttle-C (C for Cargo) is the best known of these.This proposal would replace everything ahead of the Orbiter’s engines with a disposable cargo container attached above a standard ET and SRB package.This could have placed up to 77 tonnes into orbit with every launch (without a crew) but in the absence of a pressing need it has never been built. (SOURCE:Shuttle-C at Globalsecurity.org)
USAF Air Launched Sortie Vehicle (early 1980s)
In the early 1980s, when the Cold War was at its chilliest, the USAF researched a mini-shuttle referred to as the Air Launched Sortie Vehicle (ALSV). This was to be a small reusable spaceplane which could be launched at short notice from virtually any location in the world, avoiding weeks of preparation on a launch pad.Its missions would include deploying and recovering small satellites (and I would imagine reconnaissance and possibly combat missions too). The ALSV would have been about the size of an F-15 fighter aircraft but would not have carried any crew. Mounted on a Shuttle-style external tank, the ASLV was to have been carried aloft to an altitude of 15-16 km by a very souped-up Boeing 747 (complete with a tail-mounted Space Shuttle Main Engine). The 747 would have made a steep climb, releasing the ALSV at the top. The mini-space drone would fire its own rocket motors to ascend to orbit.
At first glance, this does not sound an especially difficult technical challenge but research suggested that building and operating it would be complex and expensive and the project faded away.Probably today’s X-37 performs similar missions to the ALSV. (SOURCE: http://www.secretprojects.co.uk/forum/index.php/topic,2913.0/highlight,space+sortie.html )
Hermes was a proposed spaceplane studied by firstly the French government and later the European Space Agency (ESA) between 1975 and 1993.This craft was initially planned as a multi-purpose reusable ‘space truck’ capable of deploying satellites and carrying up to six ESA astronauts into orbit.It would have been essentially a miniature (19m long) version of the US Space Shuttle complete with a payload bay for deploying satellites.However detailed engineering studies showed this original concept to be beyond the contemporary state of the art, especially when the 1986 Challenger disaster brutally showed the necessity for adding a heavy emergency escape system for the crew. Inevitably the design was scaled back but it was still approved for construction by ESA in 1987. A cynic said that this less-capable Hermes could only be of use to launch two Frenchmen and a Belgian plus their packed lunch into space (this is a bit unfair as it was actually designed for a 3 tonne payload plus three person crew). After years of research, the now-unviable project was allowed to fade away before any Hermes craft were built.
Despite this less than inspiring history, Hermes has had a huge influence on European space activities right up to the present:the mighty Ariane 5 rocket, central to ESA’s access to space, was originally designed to launch the Hermes into space.After Hermes was cancelled, Ariane 5 development continued. Being designed to carry a 21 tonne spaceplane explains why this rocket is rather large for a mere commercial satellite launcher.This has worked out well for all concerned, as the Ariane 5 has since been cleverly adapted to deploy multiple satellites in a single launch.In theory, Ariane 5 should be among the most reliable of launch vehicles as it was designed to be ‘man-rated’, that is built to a higher standard of safety to protect its passengers.
This vehicle perhaps should not be on this list as it was actually built as a result of a huge and expensive development process and made a (single) space flight.Throughout the 1970s and 80s, the USSR was rumoured to be developing a shuttle of its own and this was expected to resemble the Starclipper in appearance.However when the Buran (“Snowstorm”) orbiter was revealed publicly in 1988 it was seen to be very, very, very similar to its American rival. Although the Buran orbiter strongly resembled its NASA counterpart there were many differences.Most significant of these was Buran’s lack of main engines as it was designed to be lifted into orbit by the gigantic Energia booster rocket.
Why was it built? In the 1970s, Soviet experts studied the proposed US Shuttle program and concluded that it made no sense at all; there simply was no need to build so sophisticated a vehicle just to place a handful of communication and weather satellites into space every year.The Soviets decided that the US Shuttle had a sinister hidden purpose, possibly as a nuclear bomber.The only way to uncover what exactly a shuttle was for was to build one themselves!
The prototype Buran shuttle was launched on 15 November 1988.There were no intrepid cosmonauts strapped in the cockpit.A life support system was not installed for this test flight and the mission was made completely automatically.The Buran orbited the Earth twice and returned to land on a specially constructed runway at Baikonur Cosmodrome.But after this triumph, things went awry, the planned follow on missions with a crew, including cargo runs to the Mir space station, kept being postponed.The vehicle and its sister ships under construction never left Earth again.A declining Soviet economy slowly killed the project which officially ended in 1993, so the first shuttle to visit the Mir space station was Discovery in 1995. Eight full-size test vehicles and five production Buran craft were built and several of these are now on show at sites in Russia and Germany.
The Buran which actually flew in space was carefully stored for many years at the Baikonur Cosmodrome but in 2002 the vehicle was destroyed when its hangar collapsed killing seven workers. Creating Buran (and the also abandoned Energia booster) bankrupted the Russian space program with effects which have lasted to the present.
Shuttle II (1985-1988)
The Shuttle had not been ‘operational’ for long before NASA began looking at plans for a replacement vehicle.This would be based on lessons learned in developing the Shuttle, leading to a more efficient vehicle meant to enter service about the year 2000.Part way through this design study, Challenger was lost, and improving the chances of the crew surviving a disaster became a priority. Several designs were proposed, the best known two are the NASA Langely Research Center (LaRC) version and the Johnson Space Center design shown above. Shuttle II actually would have a space station to fly to (the then-planned Space Station Freedom) and servicing and supplying it was to be its primary duty. It could transport perhaps 10 tonnes of payload into orbit plus eleven astronauts, eight of whom would be passengers travelling to or from a tour of duty on the Space Station.
Constructed from light weight composite materials, a Shuttle II would be lighter but more powerful than its predecessor. The power at launch came from a single Space Transportation Main Engine (STME, an improved Space Shuttle Main Engine) and twin Space Transportation Boost Engines (STBEs). The STBEs would be mounted over the wings along with a pair of drop tanks. The empty tanks and STBEs would be jettisoned during the ascent and the STBEs would be recovered for reuse. This intriguing design was allowed to wither on the vine and the Shuttle had to soldier on beyond the year 2000. (SOURCE: JSC’s Shuttle II (1988) at Beyond Apollo.)
Lockheed Martin VentureStar (1996-2001)
By the mid-90s, it was clear the Shuttle fleet had less than twenty years of life left; it really was time to seriously think about replacing it.The planned successor was the Reusable Launch Vehicle (RLV), a cheap to run and safe craft which normally would not need a crew but could carry astronauts when necessary.This was still an ambitious goal and NASA decided to pay for a scaled-down vehicle to demonstrate the concept, this was called the X-33.The agency looked at designs from Rockwell and McDonnell Douglas but finally chose a design from Lockheed Martin based on a 128 ft long craft which Lockheed Martin called the VentureStar (which bore a resemblance to the Starclipper of thirty years before). Lockheed Martin’s X-33 was about half the length of the VentureStar.
Designed to carry a 20 tonne payload to LEO, Lockheed Martin’s VentureStar was to be a single-stage-to-orbit reusable spaceplane design.Like the Shuttle, it would take off vertically and glide to a landing.A VentureStar would not need to use solid rocket boosters, instead its design would incorporate an exotic linear aerospike engine.Rather than being covered in thousands of fiddly tiles, it was to be covered in an advanced metallic heat shield. As the name suggests, VentureStar was to be a commercial enterprise, and customers such as NASA would have leased the vehicle as needed. Lockheed Martin claimed their VentureStar could launch satellites into orbit at about 1/10 the cost of the Shuttle.
The X-33 was meant to fly 15 suborbital hops to almost 76 km altitude, reaching Mach 13 in the process, to prove that the VentureStar was feasible but in fact it achieved the exact opposite without ever leaving the ground. Construction of the X-33 was about 85% complete when the program was cancelled by NASA in 2001, after a long series of technical difficulties.The demonstrator was too heavy and a crucial component, a composite liquid hydrogen tank ,was plagued with problems. A full-size vehicle could only meet worse problems.Once again the Shuttle seemed impossible to replace.(James Cameron apparently liked the name VentureStar so much that he used it for the starship in the 2009 movie Avatar). (SOURCE: The X-Planes: X-1 to X-45, Jay Miller, MCP, 2001).
This year the Shuttle program will finally end. Despite the ingenuity of generations of engineers, there is no winged reusable spaceplane ready to replace it.I think that’s rather sad.The next development in US spaceflight will be the introduction some years from now of a yet to be chosen commercially-supplied space craft, One of the contenders, SpaceDev’s Dreamchaser is a small winged craft. I wonder if it will ever fly?
Space Shuttle:The History of the National Space Transportation System, Dennis R. Jenkins, Speciality Press, 2001.
NASA Space Shuttle Manual:An Insight Into the Design, Construction and Operation of the NASA Space Shuttle, David Baker, Haynes, 2011
Space Shuttle Launch System 1972-2004, Mark Lardas, Osprey, 2004
Article by Colin Johnston, Science Education Director)