Back in December 2009, with great fanfare, space tourism company Virgin Galactic unveiled the vehicles their fare-paying passengers will ride in as they ascend into space. Built by the Spaceship Company (a coventure of Virgin and that supremely adventurous aircraft manufacturer Scaled Composites), the pair are engineering marvels. The huge yet elegant White Knight Two jet aircraft has a 43 m (141 ft) wingspan. Its payload is the SpaceShipTwo spaceplane, a considerably larger offspring of the SpaceShipOne which won the Ansari X-Prize in 2004. Since then progress has been much slower than Virgin Galactic anticipated (the enterprise was announced in 2004; flights to space were to begin in 2007).
If all goes well, in the near future (next year at the very earliest) a White Knight Two will carry a SpaceShipTwo spaceplane to an altitude of 15 km (9.3 miles) and release it. The SpaceShipTwo will fire its rocket and blaze upwards, reaching a peak altitude of between 50 miles to 110 km (68 miles) before gliding home. The six passengers will have the time of their lives, enjoying a few minutes of micro-gravity and stunning views of the Earth. The age of routine spaceflight will finally have arrived. Hopefully.
(UPDATE: in 2014 Virgin Galactic quietly admitted the SpaceShip Two craft will probably only be able to carry passengers to 50 mile altitudes, missing the internationally accepted boundary of space. However in the 1960s, the US armed services awarded Astronaut Badges to pilots who flew about 50 miles and based on this Virgin Galactic intends to define space as starting 50 miles up.)
Just to clear up a common misconception, SpaceShipTwo will not fly into orbit, nor can it dock with the ISS or any future orbital hotel. Limited to a maximum speed of 4000 km/h (2500 mph), it simply cannot reach the velocity of 28 000 km/h (17 400 mph) needed for a Low Earth Orbit (as one wit has pointed out Virgin Galactic passengers will not reach LEO, never mind LIBRA, VIRGO or any other constellation). An orbital vehicle could be designed to fit under White Knight Two, but to meet the weight considerations it would be of necessity a tiny, one-person pod, not unlike an early space capsule. Rather than holidays in space, Virgin Galactic is selling the ultimate in exciting but brief stunt flights in a rocket plane.
My main reason for being sceptical about the claims of Virgin Galactic (and its rather insubstantial competitors) is the possible safety of rocket planes (or lack thereof). Burt Rutan, founder of Scaled Composites, has said that Virgin’s vehicle “is designed to be at least as safe as the early airliners in the 1920s”. To anyone aware of the history of aviation, this statement is not particularly reassuring.
There once was a vogue for rocket-powered aircraft. Their speed, rate of climb and ability to attain great altitudes was superior to even jet aircraft. The major aircraft-building nations between 1940 and 1975 spent a lot of money researching rocket planes, including flying a series of experimental prototypes. Nazi Germany even put one into mass production. More than 400 bat-like Me 163 Komets were built to defend the Third Reich from Allied bombers (although only a few dozen were used operationally). Yet SpaceShipTwo is the first production rocket plane in decades. Why? Part of the answer is that developments in jet engine technology side-lined the rocket as an aviation powerplant. However there was another important reason: rocket planes crashed very often. A liquid-fuelled rocket engine is a very complex piece of engineering with many components capable of potential (and often catastrophic) failure. This was tragically demonstrated in July 2009 when three engineers were killed when a prototype of SpaceShipTwo’s rocket motor exploded as it was being fuelled. A rocket plane is full of very explosive propellants and flies at high speeds where any structural failure will bring disaster so quickly no pilot could react. The Me 163 referred to above is said to have killed more German pilots in accidents than Allied aircrew in combat.
Here are some numbers. They cover only rocket planes belonging to the UK and USA as those of other nations are not well-documented. In a thirty year period starting in 1947, just 16 rocket planes of seven basic types (Bell X-1 and X-2, Douglas Skyrocket, NAA X-15, Northrop HL-10, SARO SR53 and Martin X-24) made 846 flights (compared to thousands of jet aircraft making hundreds of thousands of flights in the same period). Ten of these aircraft were lost in crashes, five of them fatal. Two of these crashes can be attributed to pilot error and can be ignored. The rest were the result of technical problems with the rocket plane itself. These figures indicate an accident rate of about 1 in 105! This risk may be acceptable for volunteer test pilots, but are fare paying passengers prepared to face it? The Space Shuttle in comparison suffered two fatal crashes in 135 flights. (NB after publishing this, I looked at these figures and discovered that I had not actually counted the flights of the Skyrocket and SR53 in the total, I have now fixed that error, making the accident rate much better. Mea culpa! Further note, I have not counted aircraft fitted with RATO gear to assist their take-off either as they are not at all comparable to aircraft which rely on liquid-fuelled rocket motors for propulsion.)
Perhaps this does not mean there are grounds for concern. Travel by conventional aircraft was once very dangerous, but nowadays by several yardsticks it is among the safest modes of transport. If a similar improvement to rocket-propelled aircraft has occurred – and I have no doubts that this is achievable – the safety of space tourists will be assured. However it is unclear if such improvement has happened. Sad to say, but the safety of modern Boeings and Airbuses is based in part on the lessons learned through thousands of air accidents. Some of the historical rocket plane accidents could have been avoided thanks to lessons learned, but they were very specific to the designs of the vehicles involved. We do not have enough experience of rocket-powered craft operating at the edge of space. SpaceShipOne was (controversially) retired after only three flights above 100km. Passenger aircraft must make thousands of test flights before they are certified. I am not sure that the Spaceship Company can afford to do this with SpaceShipTwo.
I am sorry to say this but sooner or later a space tourism craft will be lost and almost certainly passengers will be killed. What happens next? Our society is very safety conscious and the vehicle’s owner will find themselves in court (remember only the very wealthy will be able to afford space tourism tickets – their relatives may be able to afford the sharpest lawyers). Rather as fear of being sued for malpractice has allegedly forced some doctors out of medicine, we may find space tourism companies shutting shop to avoid litigation.
I very much hope that I am wrong but I suspect space tourism in the Virgin Galactic mode is a false dawn. I fear the first crash of a space tourism vehicle will do as much harm to commercial spaceflight as the Hindenburg crash did for travel by airship.
(UPDATE: On 31 October 2014 I was distressed to hear that a Virgin Galactic SpaceShipTwo under test had been lost. One crew member perished while the second survived. The thoughts of all of us at Armagh Planetarium are with the families of both crew members and we hope the survivor makes a speedy and complete recovery from his injuries.)
(Article by Colin Johnston, Science Education Director)