Science

WAVERIDER, PART 1 – A SPACECRAFT  IN WAITING

by Duncan Lunan

The Waverider concept was devised in March 1957 by Prof. Terence Nonweiler of Queen’s College, Belfast, during work on a re-entry vehicle, intended for a manned spacecraft in the British space programme based on the Blue Streak missile.  The project was cancelled by the Macmillan government, but work on Waverider continued at the Royal Aircraft Establishment, Farnborough – mainly examining Waverider’s potential as a Mach 6 airliner.    

In 1962 Nonweiler became Professor of Aerodynamics and Fluid Mechanics at Glasgow University, and in March he spoke on ‘The Future in Space’ to the Scottish Branch of the British Interplanetary Society.  He became a member of the branch, and remained one the following year when it became ASTRA, the Association in Scotland for Technology and  Research in Astronautics, which was Scotland’s national spaceflight society for the next 50 years.  In 1977 it adopted Waverider as its flagship, which appeared in many versions of the ASTRA logo thereafter.

Fig. 1. Prof. Terence Nonweiler with origami ‘teaching aid’, DL at rear (Ian Girdwood, 1988).

In 1987 Nonweiler demonstrated with the original piece of paper  (“a well-worn teaching aid”, Fig. 1)  how he had invented Waverider by origami, while trying to simplify the shockwave calculations for the flat underside of what was called ‘the Pyramid Wing’.  The late Dr. Bill Hilton of Armstrong-Whitworth had suggested hollowing the underside to achieve that effect, and Nonweiler evolved a wing shape for hypersonic flight which had the profile of an inverted ‘V’, called the ‘caret wing’, because from the rear it looks like a circumflex mark or printer’s caret  (Fig. 2).   At airspeeds above Mach 2.4, it would generate a plane shockwave below it, attached to the leading edges;  the energy normally dissipated in a sonic boom is harnessed to generate lift, hence the ‘Waverider’ name.  The shape of the cavity and the planform of the vehicle are directly related:  a delta planform dictates a caret wing, a Concorde-type planform requires a cavity shaped like a Gothic arch, which the Royal Aircraft Establishment evolved for their Mach 6 airliner design  (Fig. 3).  For best performance the wing-loading should be low, making the Waverider a very efficient glider.    

His classic paper ‘Delta Wings of Shapes Amenable to Exact Shock-Wave Theory’ was published by the Journal of the Royal Aeronautical Society in January 1963, and earned him that society’s Gold Medal, but it was two to three years later before the concept briefly came into the public eye.   Newspaper articles featured the Mach 6 airliner work and the prospect of reaching Australia in 90 minutes, leading to an extremely contrived appearance on a Scottish Television programme, in which news figures of the day were supposedly discovered in a Glasgow restaurant:  Prof. and Mrs. Nonweiler just happened to have brought a Waverider model with them to dinner.  Afterwards I asked Terence about the obvious geometrical problems of launching it and landing it as an airliner, but was disappointed to learn that Waverider was still a theoretical concept, which didn’t yet even include control surfaces.

In 1967 Nonweiler took part in an ASTRA discussion project which led to my book Man and the Stars  (Souvenir Press, 1974).  Terence strongly advocated winged space vehicles for delivery to planetary surfaces, and for landing in unknown terrain, he insisted on ‘time to enquire’ over the landing site – best attained with a low-wing-loading glider such as the Waverider.  He dismissed the argument that more sophisticated systems than wings would become available:  where you have a planet with an atmosphere, he maintained, a wing, making use of that atmosphere’s properties, is more elegant than anything which wastes energy staying aloft by other means.

We followed the Interstellar Project with one on the exploration and development of the Solar System, eventually published as my New Worlds for Old  (David & Charles, 1979) and Man and the Planets  (Ashgrove Press, 1983).  By then the Space Shuttle design had been finalised, and Nonweiler was highly critical of it  –  sad to say, he was right on all points.  But Terence had an alternative to suggest.  He outlined the Waverider principle in more detail than we’d heard it before, and it captured everyone’s imaginations.   Even on the night, novel ideas for Waverider applications flew around;  by our seminar at the project midpoint in June 1974, a good deal of headway had already been made and preliminary artwork by Ed Buckley and Gavin Roberts was on display.

Fig. 4. Gothic Arch Waverider in the atmosphere of Jupiter, by Ed Buckley, 1975, for ‘Man and the Planets’

We proposed a new class of planetary missions dubbed ‘gliding entry’, to distinguish them from the direct entry missions conducted or planned at that time.  Waverider could be used for prolonged exploration of the upper layers of Earth’s atmosphere, so far sampled only by vertical sounding rockets;  but it could map the ionosphere of Jupiter  (Fig. 4), which is multi-layered and deep, whereas the Galileo entry probe went through it in seconds.  Because the most intense plasma would be concentrated below Waverider during atmosphere entry, it should be possible to maintain contact from overhead, or from Earth in a planetary mission, through the entry phase.  For extended missions in the atmospheres of Venus, Jupiter and Titan, balloons are at the mercy of the winds, limiting the study to one airstream, unless reaching another by rising or falling;  their usefulness for surface studies is limited.  When deployed over Venus in 1986, their lifetimes were short;  Waveriders could cut across airstreams for more comprehensive sampling, and at low speed, would remain aloft almost indefinitely in denser atmosphere layers.  (More on this next week.)

Fig. 5. Caret wing Waverider with deck cargo probes approaching Titan, cover by Gavin Roberts, 1981, for ‘Man & the Planets’

On Mars, Venus and Titan, Waveriders could deliver payloads accurately to preselected targets.  Since they travel at a high angle of attack during entry, we believed that landers could be carried as ‘deck cargo’  (Fig. 5), without having to fit into thermally protective aeroshells – although Gordon Ross of ASTRA, and JPL and the University of Maryland, later discovered independently that even at high Mach numbers there has to be smooth flow over the upper surface to realise Waverider’s theoretical performance.  As Nonweiler said, “one would stop short of having an open cockpit.”  Waveriders could perform extended gliding missions over Mars, flying down Valles Marineris and other chasms, for example, or spiralling down Olympus Mons for close-ups of the mysterious cliffs at its base  (Fig. 6).  Stalling speed in the Martian atmosphere would be about 400 kph, comparable to the touchdown speed of the Space Shuttle on Earth – not good for landing conventional payloads, but a caret Waverider makes a very effective penetrator.

Fig. 6. Caret wing Waverider approaching Mars, Tharsis Ridge and Valles Mariners on right, by Gavin Roberts for ‘New Worlds for Old’

There’s concern in the developing world that the poorer countries won’t benefit from exploiting the Solar System’s resources, and the gap between rich and poor nations will widen.  The United Nations Moon Treaty hasn’t been signed by Britain or the USA,  but the 1967 Treaty on the Peaceful Uses of Outer Space specifies that extraterrestrial resources are the common heritage of mankind.  When the resources of the Moon and the planets are developed, it will have to be on an international basis, with safeguards for developing nations’ rights.  Waverider’s low wing-loading gives a landing ‘footprint’, descending from space, which literally envelops the Earth, and touchdown speed less than 160 kph;  a delivery vehicle which can land anywhere on Earth, on ordinary runways, will have great political importance.   Other ideas from the Man and the Planets discussions suggested that Waveriders’ future  rôle could be comparable to Containers in the late 20th century.

I presented these ideas at the L5 Society (Western Europe) Conference in 1977, and an abridged version appeared in the Journal of the British Interplanetary Society, January 1982.  That month, Gordon Ross and John Bonsor proposed an ASTRA Waverider Aerodynamic Study Programme for low-speed work, as Nonweiler had said for years that some British group should do.  Recapitulating the RAE research, the first ‘M’ configuration proved highly unstable in pitch, on its one test flight, and ended its days as a rocket-powered boat  (Fig. 7).   Counting the basic caret wing as Mark I and the M-wing as Mark II, the Mark V was a caret wing with a vertical stabiliser like the RAE airliner’s, but optimised for Mach 3  (Fig. 8).

Fig. 9. Mk VI Waverider with stabiliser fins, 1985

In 1983, Rocket Propulsion Systems offered to launch a model at over Mach 4, at 30 km. altitude, on a flight of their planned ‘Tiger’ rocket.  The offer came to nothing, but ASTRA conducted smaller-scale tests in 1985 and 1988.  The first, witnessed by Dr. James Randolph of the Jet Propulsion Laboratory, Pasadena, released a small Waverider into spiral descent from approximately 1000 feet, and although the glider wasn’t recovered, we claim the first rocket launch of a Waverider into stable free flight.  We also claim the first free flight, hand-launched earlier that year  (Fig. 9), but the USAF disputes this:  they claim to have achieved an attached shockwave with the turned-down wingtips of the XB-70B prototype hypersonic bomber, but even if they did, it wasn’t a true Waverider because it had a conventional aerofoil wing.  No such claims have been made for Britain’s Blue Steel cruise missile, though it flew even earlier at over Mach 3 and had similar wingtips.

When I was keynote speaker at the ‘View from Earth 1984’ in California, I mentioned Waverider’s possibilities, and was invited to speak at JPL.  Dr. Randolph was interested in Waverider as a carrier for the Starprobe project  (Fig.10), to send an instrumented vehicle to within four solar radii  (3 million km.)  of the surface of the Sun  (Fig.11). 

It could be accomplished by Jupiter slingshot, but radiation hazards and very long flight time made that unpromising.  Aerogravity manoeuvres in the atmospheres of the inner planets could give the probe a trajectory with solar encounters every two to three months, but required a carrier with a very high lift-to-drag ratio at high Mach numbers – for which Waverider was the best candidate.  Six very exciting years followed, in which we were offered a tether-launch of a Waverider from the Space Shuttle, which never came off.  What was described as ‘the physics mission of the century’ was closely linked to our amateur group in Ayrshire, proceeding on a budget of washers – unable to afford wind-tunnel tests, we mounted a rig on top of a Ford Cortina  (Fig. 12);  press coverage led to wind-tunnel tests of a basic caret wing, at Mach 2.4 in a wind-tunnel of the Royal Military College of Science, Shrivenham, by courtesy of British Aerospace.  In 1989 we flew a radio-controlled model, another first for ASTRA  (Fig. 13).  In October 1990 the University of Maryland held the First International Hypersonic Waverider Symposium, co-sponsored by NASA  (Fig. 14).  Gordon gave a presentation on our work and ideas, unveiling his new Mark 10 shape, with equivalent capacity to the Space Shuttle but with much superior glide performance  (Fig. 15).  In one respect we were unique:  no-one else reported on flying real Waveriders.  When Gordon showed his first six Waverider models lying on the grass, a voice from the audience said, “My God, hardware!”  Almost everything else in the intensive three days of the conference was computer graphics.

Terence Nonweiler was a pacifist, and once said to me that “If having no military application means that Waverider never flies, I would consider that a small price to pay”.  Nevertheless, an ominous sign at the NASA event was the presence of the military, represented by McDonnell Douglas and the USAF Ballistic Missile Organization.  Building on theoretical work at the University of Maryland, they were advocating a new type of attached-shockwave vehicle, with a convex instead of concave underside, and a much higher lift-to-drag ratio for miliary applications.  The concept was adopted for the National Aerospace Plane, a proposed successor to the Space Shuttle, and flown successfully as the X-43 Hyper-X vehicle in 2004, followed by the X-41 HTV in 2013.  Meanwhile, the concept was broadened with NASA Ames Research Centre studies of a vehicle called SOAREX, which achieved an attached shockwave with a flat underside – that was test-flown successfully in 2003 – and all these lines of developed converged in the Boeing X-51 Hi-Fire, which succeeded on its fourth test launch from a B-52 in May 2013  (Fig. 16).  The Waverider’s versatility had now been narrowed down to simply directing an attached shockwave into the intake of a hypersonic scramjet engine, and having learned how to do that, Lockheed Martin announced that they would not be incorporating a Waverider component into the proposed successor, an uncrewed hypersonic cruise missile designated SR-72.

Fig. 16. Boeing X-51 on rocket booster for air-launch by B-52

Terence Nonweiler would probably have been glad of that, while continuing to deplore the broadening of the ‘Waverider’ name to include vehicles further and further from his original concept.  Along the way, the possible space applications have effectively been obscured:  when I offered an article on them to a US journal, the reply said that it was ‘nothing but a hypersonic missile concept which has been discarded’.  It reminded me of the 2012 dismissal of the Sighthill stone circle as “nothing but an unfinished piece of 1970s public art”.  The landscaping of the pathways round its new incarnation is at last approaching completion  (Fig. 17).  Similarly, back in 1992, Gordon Ross began work on a new generation of Waverider concepts which could yet lead to its rebirth.

Fig. 17. Sighthill stone circle from the air, late November 2022

At the 1995 Edinburgh International Science Festival, Gordon unveiled two new ‘Shapeshifter’ flex-wing designs, for a space shuttle cargo vehicle and an interplanetary probe carrier.  The latter was tested in the Architecture Department wind-tunnel at Glasgow School of Art, where he worked in the industrial design unit.  He went on to a whole new family of flexible airfoils, some tested in subsonic and supersonic tunnels at Imperial College, London, and investigated manufacturing a sample of the woven carbon-fibre fabric he designed for the Shapeshifter, for thermal testing at the Art School, which has the plasma torch equipment needed.  The estimated cost, £10,000, was far beyond us.

Fig. 18 ASTRA flex-wing Waverider Space Station lifeboat, Gordon Ross, 1996

At the Astronomical Society of Edinburgh in January 1996, Gordon and I proposed a flex-wing Waverider as a one-person escape craft for the International Space Station  (Fig. 18).  It would bring an individual back, for personal or medical reasons, without evacuating half the ISS crew by Soyuz, or all of them by Shuttle or a lifeboat like the cancelled X-38  (Fig. 19). 

Fig. 19. Space lifeboat launch from a Space Station multiple adaptor, by Andy Paterson, 1997

A wrap-around life-support garment would maintain cardiac stimulus, intravenous drip or other medical needs during return to Earth  (Fig. 20);  highly manoeuvrable, with a large cross-range footprint  (Fig. 21), landing vertically by steerable parachute, the craft would deliver a casualty straight to the best hospital to deal with the problem  (Fig. 22).  A simplified version would have let the crew of the stricken Columbia return individually to Earth;  the life-support system would have major spinoff applications.  But to date it hasn’t attracted funding, despite presentations to NASA and to Astrium UK. 

Fig. 22. ASTRA lifeboat landing, by Andy Paterson, 1997

Afterword

The history of Waverider including the evolution of the military versions is discussed in much more detail by Duncan Lunan in ‘Waverider Spacecraft, a History’, (Ian Sales, ed., Rocket Science, Mutation Press, May 2012), and in ‘Waverider, A New Chronology’, American Institute of Aeronautics & Astronautics, 20th Hypersonics Conference, Strathclyde University, 7th July 2015.  Gordon Ross’s flex-wing Waverider designs including the Space Lifeboat were published in ASTRA’s journal Asgard, as ‘Hypersonic Flexwings as Ultralight Waverider Vehicles, a Conceptual Study’, and ‘Mayday in Orbit’, May 1997, also in ‘Promoting UK Involvement in the ISS:  a Space Station Lifeboat?’, Space Policy, December 2001.  Off-planet applications will be discussed next week.

(To be continued.)  

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