NEWS
On December 13, 2011, Paul G. Allen, the billionaire co-founder of Microsoft, disclosed at a press conference in Seattle that he was entering the rocket business with a concept seldom used till now: a plane that can take off the conventional way and then at 30,000 ft, launch a rocket to orbit, carrying with it satellites, supplies and eventually, even people. “One has a certain number of dreams in one’s life to fulfill,” said Allen, an avid philanthropist who has also financed efforts like a radio telescope listening for alien transmissions. “… and this is a dream that I am very excited about,” he enthused.

VIEWS
Much before the US space shuttle ‘Atlantis’ touch down at the Kennedy Space Center on July 21, 2011, which officially culminated the National Aeronautics and Space Administration (NASA) space shuttle programme, a substantial number of private players started developing alternative means—often with ‘out of the box’ thinking’—to keep the US in the forefront of global efforts for space exploration. Billionaire Allen’s endeavour to realise his extraordinary dream is yet another step in that direction; but with a difference.

Paul G. Allen’s newly founded company StratoLaunch Systems will build an airplane that will be larger and heavier than the ‘Spruce Goose’, Howard Hughes’s record-setting flying boat that flew, just once, in 1947. With a wingspan that will stretch 385 ft—bigger than a football field—it will dwarf Airbus A380, a doubledecker giant, which is the biggest commercial passenger in operational service today. It will incredibly weigh over 540 tonnes including the fully-fuelled launch vehicle. The aircraft will be powered by six 46,000—66,500 lb thrust-range jet engines that are planned to be sourced from Boeing 747-400 series engines. Other components, including the flight deck and landing gear, will also come from the 400-series, giving it a range of 2,200 km (1,200 nm) on air launch missions. A Falcon 9-derivative two-stage liquid-fuelled air-launched winged vehicle will be developed by SpaceX. The launch vehicle will have a mass of approximately 220 tonnes and will have the goal of inserting a 6,100 kg (13,000 lb) payload into low earth orbit. So, what is the big deal?

Actually, the phenomena known as ‘air launch to orbit’ is nothing new and has been successfully deployed earlier, such as by the ‘Pegasus’ air launch system with as many as 40 launches till date (35 successful). But the difference lies in the size and therefore the ability to put into low earth orbit (LEO) big-sized payloads to meet the present-day operational requirements while maintaining all the advantages of air launch over launches from costly and static ground stations.

The main advantage of the air launch provider is the inherent flexibility. Air launch to orbit offers the potential for aircraft-like operations such as launch on demand and is also less subject to launch-constraining weather. This allows the mother aircraft to fly in adverse weather conditions as well as fly to better launch points. The other advantages include reduced scheduling constraints, minimum launch site requirements and reduced range and safety concerns, but more importantly, the highly desirable equatorial launch capability, which increases performance and is a requirement for some mission orbits.

Another big advantage of air launching is the considerable reduction in the amount of propellant. This is because the carrier aircraft is able to lift the rocket to altitude much more efficiently with the use of turbojet engines. With more than 70 per cent of the atmospheric mass and 50 per cent of the atmospheric pressure lying below 30,000 ft amsl (above mean sea level), the mother aircraft would have already won half the battle of overcoming gravitational forces, enabling a much easier, safer and cost-effective space launch. Launching at altitude also presents significant performance benefits to the rocket. The high horizontal speed provided by the aircraft gives the rocket a large initial velocity with as much as 15 per cent reduction in the amount of effort required to reach the desired orbit over a vertical launch case. For a comparison, the space shuttle stack with a launch mass of 2,030 tonnes could put 24 tonnes of payload in LEO while the Space-X Falcon Air with a launch mass of just 220 tonnes will get there with a phenomenal 6.1 tonne-payload, increasing its effectiveness by an order of magnitude.