As SpaceX has been developing and testing its reusable rocket technology, the European Space Agency (ESA) has been watching and apparently thinking that reusable rocket technology is a good idea. For the past few years the ESA has been woking on their own version of a reusable launch system, but they're taking a very different approach. They claim that their design has some real advantages over the SpaceX design, and they may be right.
Following in the tradition of most american rocketry, SpaceX's Falcon 9-R rocket, their current partially reusable design, puts the payload on top of a two stage launch vehicle. The bottom, or booster stage is steerable and landbale in an upright position. This is a very complicated feat to pull off, with very little room for error, and landing an entire half of a rocket, which includes the fuel tank, costs the Falcon 9-R in terms of the weight it can carry and the altitude it can reach with those weights.
After watching the Space Shuttle and the Falcon 9-R, the ESA has decided to take a different approach, a very different approach they call Adeline - short for Advanced Expendable Launcher with Innovative engine Economy. The I and the E might be a little bit of a stretch, but...: In any case, the ESA has decided to take all of the really expensive stuff, the avionics, the rocket engine, and the propulsion bay and put them in a bottom stage that's not all that big. They've equipped it with wings and propellers and landing gear, and that's all that they re-use. It's certainly a different approach, and there are definite advantages: Adeline can land on a runway, and because it will be land under power, the ESA can choose the runway, potentially even well into the landing. They could even change the time of the landing if they needed to. And think about it: how valuable are fuel tanks? What's the real value in being able to re-use them?
The list of Adeline design advantages goes on: After the landable stage of Falcon 9-R separates from its second stage, it has to fall for some time through the atmosphere. That's not easy on a rocket motor, which is at the leading edge of the vehicle as it falls back to earth. The Adeline will go straight from booster to winged flight, subjecting it's rocket motor to none of the atmospheric punishment that the Falcon 9-R is forced to withstand. Adeline also has a much smaller penalty on its performance for being reusable than the Falcon 9-R., and because Adeline houses all of its expensive bits in a fairly small reusable lower stage, the ESA will be able to reuse 80 percent of Adeline's economic value - the engine, avionics and propulsion bay. So, is Adeline a better system? It's first launch is scheduled for 2025, so we may have to wait a while to find out.