Airbus Defence and Space

Nail-biting moments, by Horst Holsten

In 1979, Horst Holsten was project manager for the Ariane second stage at CNES, before becoming Head of Ariane at Airbus Defence and Space (then MBB-ERNO) in Bremen in 1986. Here is his first-hand account.

“Everything was going according to plan for the maiden flight of the Ariane on 15 December 1979 – the launch preparations, fuelling-up and the countdown, too …five, four, three, two, one, zero: ignition of the four first-stage engines. Yellowish brown gas came up out of the exhaust ducts, but the rocket didn’t budge an inch, it stayed firmly on the ground and the engines had to be shut down again. What had happened? An error message from a pressure sensor in one of the four engines prevented the support arm from disengaging. We were all so disappointed, worried that all our efforts might have been for nothing. What about all those calculations, analyses and tests? This setback wasn’t going to stop us, though! The rocket was de-fuelled, cleaned, given a thorough check and prepared for a new launch attempt. Eight days and nights later, it was 23 December and everything was ready again – yet our hopes were to be dashed once more. This time the automatic launch sequence was halted by the computer in the control room because a valve failed to produce a check-back signal. We managed to establish very quickly that the valve was working properly; it was just that the electrical check-back signal was faulty.

The first Ariane on the launch pad.
The first Ariane on the launch pad.

There was just one last launch attempt left, since we'd used up our supplies of helium and, of course, without helium, which is used to pressurise the fuel tanks, you can't launch. This really was our very last shot. On 24 December, Christmas Eve 1979, that moment had arrived. The remaining helium was in the stage tanks, the check-back signal from the valve was manually overridden at the critical moment during the launch sequence and … the rocket lifted off, heading off into the bright blue sky. There was only muted applause in the control bunker, as now the interminable wait – with emotions ranging between hope and trepidation – until the end of the flight began. For the team from Bremen the critical moment came after the first stage separated. Would ‘our’ second stage deliver the power it was meant to? It did. The engine ignited, the pressure built up in the tanks, everything went to plan, and the trajectory was just perfect. Towards the end of its flight, a moment of nail-biting tension – unexpected vibrations (Pogo valves, as it later turned out) – but everything went well through to the burnout.

The upper stage also flew perfectly and when the words “payload separation” were heard, a phenomenal cheer went up in the control bunker. It was such a relief after the weeks of tension and more than one of us had tears (of joy) in their eyes: the successful maiden flight of a completely new launch system – how often had something like that been achieved before?! As well as the second stage from Airbus Defence and Space Bremen, Airbus Defence and Space Ottobrunn (then MBB) was also involved in this programme, supplying the engine for the upper stage. It was the start of a success story that has continued to this day.

Soon Ariane 1 would no longer be able to meet the payload requirements and so it was upgraded with additional boosters. Then came the day on which Ariane 4 was launched for the first time with four of these boosters. The date was 5 June 1989. All four boosters ignited at the same time, worked like clockwork in flight and separated simultaneously from the first stage. It was the birth of the European space industry’s workhorse, as this version would subsequently be dubbed. And much of the credit must go to Werner Inden, sadly no longer with us, who as director of the Ariane programme was responsible for ensuring that the company’s technical and cost constraints were met.

Due to the proven reliability of these stages, it was not surprising that the development of the Ariane 5 EPS upper stage was entrusted to Germany. Airbus Defence and Space Bremen was, and still is, responsible for the upper stage and the Attitude Control System (SCA), while Airbus Defence and Space Ottobrunn supplied the Aestus engine. During the maiden flight – of which we all have some painful memories – the rocket exploded shortly after launch. Some nail-biting moments also accompanied the second launch on 30 October 1997. The SCA had to correct an unplanned roll movement, using up 90% of its fuel in the process. Would there still be enough fuel for the half-hour flight of the upper stage? Fortunately, there was: the upper stage flew so smoothly that it successfully completed its mission. Huge relief, pats on the back and once again the feeling of working as part of one big, dedicated team, which makes this kind of success possible. So this is how we laid the foundations for the centres of competence for upper stages in Bremen and propulsion systems in Ottobrunn. Today, both the ESC-A cryogenic upper stage as well as the upper stages for the next generation of rockets are being developed and integrated in Germany. Who would have thought that, back in December 1979?”

Launcher SystemArianeAriane 4Ariane 5