- Published: Thursday, 24 December 2015 07:31
With the recent success of SpaceX and Blue Origin, several people have asked us whether winged boosters has a future. The answer is of course a resounding yes...
Firstly, the SpaceX and Blue Origin landings were amazing technological feats, and we wish to congratulate them wholeheartedly.These companies are visionary leaders that are responsible for the most significant progress in the launch industry in 30 years. As such we do not wish to criticise them in any way. We would however like to point out that further advancements can be made, and that the race to cost effective launch vehicle reusability is far from over.
As the head of France’s Space Agency (CNES) explained, returning a rocket to the launch site is not quite the same as reusing it:
A crucial advantage of the ALV winged boosters is that our rocket engines are only operated for about 2 minutes during the ascent, whereas the rocket-return vehicles have to burn some of their rocket engines for several minutes to reduce their velocity and for the landing. This significantly shortens their life.
The powerful first stage rocket engines are the most expensive part of the entire launch vehicle, and thus the part that is most worth saving and reusing. Compare, for example, the Airbus Adeline proposal which only returns the first stage rocket engines to earth and nothing else. At the same time a typical rocket engine only has a useful life of only a few minutes before it requires a full rebuild or is scrapped. Therefore we believe it makes a lot of sense to use the rocket engines for as short a period as possible (i.e. only during the ascent), saving their precious lives for the next launch.
The ALV also requires no landing platform in the middle of the ocean, since we return to a runway on dry land near the launch site. We note that rocket powered vehicles can also return to the launch site, but this requires the rocket engines to be burned even longer for turning around and flying back. This further decreases their life significantly. And of course a large amount of additional propellant is required, which is dead weight during the ascent (just like our aero engine and wing are). Rocket powered return and landing also requires engines that are both restartable in flight and can be throttled, which significantly increases engine complexity.
One of the further big advantages of the ALV booster concept is that it is essentially a very large UAV when returning. The entire return flight can be therefore be tested by taking off, flying and landing like a conventional aircraft from a runway. This massively reduces development complexity, since we don't have to launch a vehicle (which is very expensive) every time we wish to test an aspect of the return flight or landing. And we are leveraging 100 years of aviation experience, which we believe is the key to future aircraft-like operations.
For the ALV project, we are sticking to our “as simple as possible” philosophy. We are inspired by the simplicity of vehicles like the Russian Soyuz, which has flown more times than almost all other launch vehicles combined. More complex vehicles like the Space Shuttle has come and gone, accompanied by massive costs. While the reliable, simple and low-cost Soyuz lower stages are still almost identical to the vehicle that launched Sputnik and Yuri Gagarin in the 1950’s and early 60's.
Our focus on simplicity (especially on development simplicity) has enabled us to create a clear low-cost roadmap from the ALV-0 test vehicle (which first flew in December 2015), to the ALV-2 small satellite (5-50kg payload) launch vehicle.