Europe’s bid to slash the cost of access to space has received a boost in the form of a reusable rocket engine intended to cost just €1 million ($1.1 million) – compared with the €10 million cost of the disposable Vulcain2 that powers the Ariane 5 heavy lifter.

At the Paris air show in June, the European Space Agency signed a contract with Ariane prime contractor ArianeGroup to develop a demonstrator called Prometheus. The reusable liquid oxygen-methane engine concept will undergo ground testing in 2020 and is ultimately intended to power European launchers from 2030.

Meanwhile, ArianeGroup chief executive Alain Charmeau says, “all the stops” remain pulled out in the development of Ariane 6, set to fly from 2020. Launches are to cost €70 million, less than half the bill for Ariane 5 and on a par with the cost of a ride on SpaceX’s smaller Falcon 9. Ariane 6 features a modular design and developments of proven Ariane 5 technology, including an iteration of Vulcain2. Its solid fuel boosters – two or four, depending on payload mass – will double as the first stage of the in-development Vega C light launcher.

All of this European activity is in great part a response to competitive pressure from SpaceX, whose prices have shaken up the launch market. Falcon 9 is not technically radical. But, with several hundred million dollars of investment and launch contracts from a NASA eager to outsource, SpaceX has, unburdened by legacy technology or infrastructure, created a streamlined business able to undersell rivals such as Ariane 5 and the Atlas V and Delta IV launchers from US leader United Launch Alliance. Those established launchers are hugely reliable but costly; all use dispersed industrial infrastructures and technology dating to the 1980s. ULA is a Lockheed Martin-Boeing joint venture born of Cold War-era organisational priorities; Ariane rockets come together via a cumbersome network of suppliers devised not for cost efficiency but by a European political reality that has historically dictated that contracts be spread equitably across all EU member states which contribute to a programme budget.

Falcon 9

Europe’s response to SpaceX is not only the technically more efficient Ariane 6 and its smaller sister, Vega C, which is a bigger development of the current Vega and set to fly from 2019. Leaders in Brussels have made a clear statement of intent to retain an indigenous European capability to access space, and as such have stepped away from the notion of juste retour budget-spreading in favour of the consolidation of the Ariane programme. ArianeGroup is a joint venture between Ariane prime contractor Airbus and propulsion specialist Safran – the business was formally Airbus Safran Launchers until 1 July – and has recently taken control of launch operator Arianespace, which runs Europe’s space port in Kourou, French Guiana.

Hence, Europe’s launch offering now sits under one roof, from concept and design through to sales and operations. Vega, also operated by Arianespace, is provided by prime contractor ELV, owned by Avio and the Italian Space Agency. That arrangement had recently to pass scrutiny by the European competition authorities, which decided that Arianespace’s essentially in-house relationship to the Ariane 5 and 6, and also the Soyuz medium-weight lifter, would not disadvantage ELV or prospective customers of the much lighter Vega.

The European Commission and European Space Agency are essentially buying services from ArianeGroup – which, while contracted to develop launchers whose performance is dictated by the EC and ESA, must compete for their business. Critically, ArianeGroup relies on commercial business such as the orbiting of telecommunications satellites and must be cost-competitive to survive. The number of launches bought annually by European institutions – be they the EC or ESA, weather service EUMETSAT or national governments – is small compared with the large number of flights to space demanded by US counterparts whose business most typically goes, for national security or political reasons, to ULA, SpaceX or Orbital ATK.

But while industrial structure, manufacturing and design are clearly driving down launch costs, much attention is being paid to another, much more visible, approach to economy: reusability. Here again, SpaceX is making headlines, having successfully recovered main stages and engines to the ground via powered, soft landings; so far this year it has also successfully flown recovered and refurbished boosters. And, significantly, it has re-used one of its Dragon space station resupply cargo capsules.

ArianeGroup’s Prometheus engine is being billed as reusable. But as Charmeau notes, rocket motors running on cryogenic fuel are inherently restartable and in principle reusable, and in any case motors supplied for Ariane 5 rockets go through a couple of test burns on the ground before flight. The same cannot be said of solid rockets – once started they consume their fuel to exhaustion, and the nozzles are burnt, pitted and stressed beyond refurbishment. With Prometheus, reusability of course presupposes recovery after flight, and right now, Charmeau says, the development priority is very much on the engine.

Having said that, much work has been done in Europe on recovery concepts, and ESA has made clear that launcher development is an ongoing process; iterations of Ariane 6 could, later in the 2020s, include reusability. European thinking on reusability is focused on recovering the engine, which makes up the bulk of the cost of a launcher. In 2015, Airbus Defence & Space showed its Adeline (ADvanced Expendable Launcher with INnovative engine Economy) concept. This featured a detachable, winged engine housing that would, with turboprop power, fly back to a runway landing – to Cayenne’s Félix Eboué international airport, for example, just a few kilometres from Kourou.

ULA’s competitive response has been to initiate development of its own modular concept, called Vulcan, to succeed Atlas V and Delta IV in the 2020s. Like ArianeGroup, ULA’s reusability concept looks at engine recovery – but in flight, by parachute and helicopter.

From SpaceX, meanwhile, some insight into the refurbishment process came from vice president for commercial sales Jonathan Hofeller, speaking at a space insurance conference in London in June. He told the World Space Risk Forum that where it took SpaceX nearly a year to refurbish the first booster for re-use, a second was readied in a couple months. Each part, he says, is refurbished, and the plan is that if a recovered booster as a whole cannot be made as good as a new one it will be retired. SpaceX, he says, talks about “flight-proven” boosters and sees "reliability as closely coupled with reusability".

Meanwhile, one example of the suborbital New Shepherd rocket and crew capsule being developed by Blue Origin, the company founded by Amazon boss Jeff Bezos, has flown to the edge of space four times. It has yet to carry a human passenger, but the plan is to ferry paying passengers to just beyond the official 100km altitude barrier delineating Earth from space.

The aptly named Ariane Cornell, head of North American sales for New Shepherd’s very big brother, New Glenn, told the London space risk forum that Blue Origin’s suborbital programme was partly about building experience to go fully orbital. New Glenn – a very heavy lifter, being designed to put 13t to geostationary orbit or a massive 45t to low-Earth orbit – is being developed to fly in 2020. Like Falcon 9, it will land on a barge at sea, and its highly throttleable BE4 engines (being developed in conjunction with ULA) will let it touch down softly, and vertically, like Falcon 9. But where Falcon 9 uses rocket power to make a tail-first descent from space, New Glenn is being equipped with steering fins to “literally fly back”.

Experience will tell, but it should be noted that the history of reusable spacecraft is not encouraging. NASA’s Space Shuttles were intended to fly over and over, almost like an airliner, but in practice post-flight refurbishment was slow and costly. Iconic as it may have been, the Shuttle programme was a failure when measured against its objectives of slashing costs and providing the USA with airline-style access to space. Over 30 years, with as many as four orbiters in service at any time, there were just 135 Shuttle missions – on average one every 12 weeks, or less than four flights per orbiter per year. According to NASA, the cost of a typical flight was $450 million. Disposable launchers would have been cheaper, and design aspects of this very complex vehicle featured in the total loss of two orbiters, killing 14 crew.

Ariane 6

Future iterations of ESA's Ariane 6 may incorporate engine recovery and reuse technology

Airbus Defence & Space

The stress associated with launch should not be underestimated. Simple physics says it takes about 70 times as much energy to go orbital as suborbital. Cornell observed – on the topic of New Origin building experience for the orbital rocket project – that a New Shepherd suborbital launch costs just 2% of what it will cost to put a New Glenn into orbit.

Today’s reusable launcher designs benefit, of course, from the Space Shuttle experience as well as four decades of subsequent technology development. And none of them involves vehicles as complex as the Space Shuttle. SpaceX boss Elon Musk insists that reusability will slash costs and revolutionise space flight. Cornell says reusability will cut costs and hence increase demand. And, she stressed, Blue Origin’s goal – admittedly not in the near term – is to help “millions of people to live and work in space”. Musk echoes that sentiment, SpaceX’s mission statement being “to revolutionise space technology, with the ultimate goal of enabling people to live on other planets”.

But whether reusability becomes a significant factor in launch cost control remains to be seen; what is possible is not the same as what is cost-effective, and there are significant mitigating factors, even if reliability is ultimately able to match that of virgin hardware. When presenting Adeline, engineers at Airbus Defence & Space reckoned Falcon 9-style full-booster reusability could cut payload capability by a third to a half, depending on the mission, to accommodate the fuel needed to fly back from the edge of space and to lift the requisite landing gear and thermal protection needed to survive re-entry, not to mention the mass associated with structural robustness to withstand multiple flights. Fuel is cheap, though – less than $200,000 for a $60 million Falcon 9 launch, says Musk – so flying a bigger rocket than needed may be no false economy; if maximum launcher performance is needed for a particular mission, then the vehicle might not be recovered.

The same Airbus engineers reckon the Adeline idea, by focusing on a much smaller but high-value component – the engine – could cut operating costs by about 30%. Another aspect of the reusability they considered is to park a restartable, liquid-fuel rocket stage in low-Earth orbit. A main launch would deliver to this waiting “space tug” a payload and the fuel needed to carry it higher – to a 36,000km (22,000 mile) geosynchronous orbit in the case of a telecoms satellite – hence reusing a stage without having to bring it back to Earth.

By leaving much of the rocket in orbit, the space tug idea would reduce the size – and cost – of launchers. Satellites would no longer need to carry their own fuel to reach final orbit, possibly reducing their cost and increasing their capability, and tugs could be used to upgrade, repair, resupply or reposition existing satellites. At the end of their useful lives, the tugs could also be used to carry a payload to deep space or be burned up safely in the atmosphere.

Having said that, even 50 years since in-orbit docking was first realised in preparation for the Apollo Moon missions – not without hair-raising drama and no less than Neil Armstrong at the controls of Gemini 8 – such manoeuvres remain challenging and dangerous. The December 2015 Soyuz flight to the International Space Station left Russian flight controllers reportedly “worried” when an automatic docking system failure forced cosmonaut pilot Yuri Malenchenko to close the last meters manually, safely delivering himself, British astronaut Tim Peake and American Tim Kopra. A quick Google search for “docking mishap” turns up a litany of near-misses and lost spacecraft.

But SpaceX’s thinking on reusability reflects a key objective beyond mere cost-cutting, which is to accelerate the speed of operations. As Hofeller puts it, a “near-term” goal is to launch, refuel and re-launch within 24h. That focus on launch cadence is also evident in another SpaceX project, which is to introduce fully automated self-destruction in the event of a launch anomaly. That system, he says, is largely about reducing the number of people associated with a launch, and hence demand on the pad infrastructure.

There are many factors affecting cost, and the benefit of reusability may prove only marginal. In the case of Prometheus, going from €10 million to €1 million for the engine would take €9 million off of the €70 million cost of an Ariane 6 launch, notwithstanding any other cost savings realised in the construction of whatever iteration of Ariane ESA is flying by 2030.

If that €1 million engine can be flown five times, the per-flight hardware costs drops to €200,000 plus refurbishment costs. So, as long as motor refurbishment costs less than 80% of a new unit there is money to be saved in reuse. However, what isn’t clear is the total cost penalty of reusability. That is, fuel and refurbishment costs aside, how much more expensive is the construction of a component built to withstand re-entry and the strain of multiple use than one built more lightly, and with less complexity, for use-and-discard?

If the launch industry can achieve the capital cost-reduction expectations of a concept like Prometheus and the launch cadence acceleration potential of innovations like automated self-destruct, then cost of launch may be set for a dramatic overhaul in the next decade or so. Reusability may prove to be a sideshow to the real revolution.