SKYLON – the answer to UK space dreams?

It’s like this:

I would LOVE the UK to have a human spaceflight programme. I would LOVE the UK to lead the way in space exploration. I would LOVE for people around the world to look at our country and see that we are investing in science, technology and inspiring a new generation of engineers. So why am I not sold on SKYLON?

SKYLON could be the answer – a space plane that can go from runway to orbit and land back on a runway again. A fully reusable vehicle which promises cheaper launch costs and a more reliable launch system, and it’s being developed here in the UK.  The air-breathing SABRE engines that Reaction Engines are developing are the key to this, and according to Mark Hempsell, who’s worked for Reaction Engines for many years, the feeling inside the project is that it’s “achingly close to being realised”.

Skylon in a hangar - the future?

Image Credit: Reaction Engines

At a recent talk at the British Interplanetary Society, Hempsell, (who is leaving Reaction Engines to work for his own company, Hempsell Aeronautics) said we’re at an “absolutely unique point in astronautical history”. He went on to explain how SKYLON’s 4.8x13m payload bay could take 15 tonnes to Low Earth Orbit (300km) and because it’s reusable it will bring down the cost of reaching space. Cost being the fundamental thing holding back astronautics he explained.

He went through various factors, looking at the short- and long-term hopes for SKYLON. For example, in the short-term, he said that SKYLON will be fully commercial at lower-than-current launch costs (i.e. no tax-payer subsidy required to make up the launch cost). In the long term they are looking at around $10 million per launch.

Hempsell said that SKYLON will be more reliable than current launches, and since it has the option of aborting a mission and returning to Earth if there is a failure, he reckons there would be just a 1 in 20,000 chance of not getting your satellite successfully in orbit, or safely back to Earth in case of a problem. In the long-term they are looking at having reliability levels that match those of aircraft.

Availability is another key selling point. In the short-term, SKYLON could be available in a matter of months, and in the long-term they are hoping for it to be available in hours (if required – not as standard!).

So which market are they aiming for with SKYLON?

In the short-term Hempsell expects it to be a simple replacement for expendable satellite launchers, but the long-term ambitions are much grander. He says it’s a game changer, disruptive technology that could lead to a new age of space exploration – allowing people to realise those old dreams of people living in space.

The optimism continued as Hempsell explained that SKYLON can meet the requirements of the next generation European launcher. He reckons they can capture the market that ESA has. “This is a perfect match for what ESA thinks it will be doing until 2050” he says, adding that although ESA has no human spaceflight requirement at this stage, SKYLON will be sold to people who do, in the 2020s.


Image credit: Reaction Engines

He claims that SKYLON could fly to the ISS with 11.5 tonnes of payload (or 10.5 tonnes if you allow for an attachment interface – which is rather crucial if you think about it!).With a crew/cargo combination you’d be looking at being able to send up an exchange crew of three to four people, plus around two tonnes of cargo.

They are also looking at a “personnel and logistics module” that could sit in the payload bay and take around 7.8 tonnes, including a crew, consumables and around 24 passengers into space. They expect something like that to be available when they’re ready to launch.

Here’s a (somewhat outdated) video explaining the module:

SKYLON Personnel & Logistics Module from Reaction Engines Ltd on Vimeo.

So that’s the satellite launch and space tourism markets covered, what about its potential for furthering exploration? “Project Troy” was a study looking at whether SKYLON (the old version, rather than new D mark) could be useful for a Mars mission. The study “proved” that SKYLON can launch a manned mission to Mars. They looked at building spacecraft in LEO and boosting them to Mars with Hydrogen and Oxygen fuelled stages. It suggests a fleet of three craft, each with six astronauts. Fascinating. Must find out more.

Project Troy was carried out to ensure that SKYLON is future-proofed says Hempsell. Thinking ahead to possible future scenarios is a smart move, though whether I would agree it is possible to “prove” a vehicle that as yet doesn’t exist (and airframe design is not finalised) is capable of a Mars mission, I’m not sure. “SKYLON will not be a block to realising customers’ dreams” say Hempsell. It’s a bold claim.

He talked us through the concept design of the “Fluyt” stage, which was worked on by Simon Feast. This could deliver 15 tonnes to GEO, and around 12 tonnes to lunar orbit apparently.

They also looked at a post-ISS scenario, in which they envision 14 space stations situated from LEO to the lunar surface, with 104 people in space, including a space hotel.

With one operational SKYLON flying twice a week, he told us it would be possible to build a space station in LEO in just 6 weeks, and a GEO/Lunar station in 18 weeks. With two SKYLONs you could build the whole 14 station infrastructure in less than three and a half years!

It’s exciting stuff. Imagine that! – building a space station in just six weeks – with a UK space vehicle! That would certainly put us on the map as a serious space-faring nation.

So why am I not rejoicing? Why am I not leaping about and extolling the virtues of this vehicle? If it can do all of the above it really would be a game changer. What’s my problem? (Apart from the fact I think it looks like an evil whale harpoon.)

SKYLON - the future?

Image credit: Reaction Engines

My problem is that it doesn’t actually exist.

SKYLON, the thing that we keep hearing about, is not the main focus for Reaction Engines. In fact, they are not even going to create the airframe for it, someone else will. The idea for producing SKYLON is to create a customer for the engines that Reaction Engines are making. Their air-breathing engines might well be game-changing, but we’re a long way away from all the things that Hempsell was so excited to talk about.

He himself admits that the devil is in the details. He mentions an issue with docking mechanisms – they don’t want to change the one that is designed for Skylon, but that would mean satellites would have to add a special SKYLON interface mechanism in order to work with the vehicle. This would add an extra 5-10kg to the satellite says Hempsell. It might not sound much, but I’m pretty sure it’s no simple  undertaking.

For crew/cargo delivery to the ISS to be fully effective, you would require a docking system with a hatch big enough to get equipment racks through. Apparently the current ISS hatches can’t do this and you have to go through berthing modules. (Correct me if this is wrong, I’m just reporting what he said).

His solution to all this is to develop a Universal Space Interface Standard (USIS) that could be used for all applications, by all users, all the time. It sounds like a perfectly logical idea, but when you note that the ISS partners spent years developing their own international docking system standard (IDSS) and then the US decided not to include it on Orion, and Russia isn’t going to use it either, you realise that it’s (unsurprisingly) a bit more complicated than just having a good idea.

The IDSS is apparently too heavy, too small, too expensive, so there is lots of potential for something light, cheap and useful to all. This is undoubtedly true, but if major space-faring nations, working together, with a vested interest in making something work (i.e. improving access to ISS and future co-operations) can’t do it, that has to be a bit of a warning flag, no?

As he’s speaking, I note that Hempsell uses “trick”, “little trick” and “nice little trick” a few too many times for me to take all he is saying without a pinch of salt.

The talk was entitled “The Future of SKYLON”, but by the end of it I’m left with more questions than answers. Hempsell has spun a seductive tale of the future of exploration, the Moon, Mars, SKYLON, but the basic questions still hang in the air.

We’ve heard so much about the incredible stuff SKYLON“could” do, but little about the details of getting it to a point where it exists, and this is reflected in the questions at the end.

“How long, realistically, will it be until the first launch or prototype?” asks an audience member. “If money were no object, around 2020” replies Hempsell, but he thinks 2022 is more likely since politics, money and partners will limit things (though not the technology).

What about funding? Well the funding so far is for Reaction Engines, not SKYLON. The money they have for SKYLON is not huge admits Hempsell, they need more. For the SABRE engine they have some kick-off funding from ESA (€8m), £60m from government and the rest is apparently private (but that’s commercially sensitive information so he can’t say more).

There are questions about how the vehicle will be certified for human flight (rules currently being defined by the CAA, in conjunction with international agencies says Hempsell) and my question, about reliability.

It strikes me that making reliability comparisons with companies like SpaceX, is not entirely fair. How can you compare the reliability of a vehicle that exists (and is constantly evolving and improving) with one that doesn’t?

I could tell you that my rocket is going to be 100% reliable. Beat that.

I can say that, and it’s meaningless, because my rocket doesn’t exist and so there is no way of testing the assertion.  How is this any different?

Hempsell assures me they’ve done lots of work to back up their assertions and says that the difference between them and SpaceX is that their vehicle will be fully reusable, thus increasing reliability. I can’t help thinking that since SpaceX are already building and flying rockets, and moving closer to a reusable system themselves, that this still a little unfair.

Remember, even if money were no object they don’t think that they will have a vehicle until 2020, that’s plenty of time for SpaceX to keep improving their systems and reliability. They are not exactly known for hanging around with things after all.

“What about the shuttle?” I ask, “that was meant to be reusable but budget cuts changed the design – couldn’t the same thing happen to SKYLON?”. Hempsell focuses his answer on the fact that the shuttle wasn’t really reusable and had many expendable parts. Those were the bits that failed, the bits that had were new for each flight, rather than having been tested in a flight scenario first. This wouldn’t be the case with Skylon which is going to be fully reusable he asserts.

I’m still doubtful; after all, the greatest of plans can be crushed by politics and budgets. What’s to say that similar compromises won’t have to be made to get SKYLON into existence?  “When you see expendable bits on SKYLON, that’s when you know there’s a problem” says Hempsell.


But I think that there already is a problem, and that’s the unrealistic assumptions being made about everything from the financing, to the ease of persuading existing space powers to adopt new interfaces. The throwaway comment he made about adding another runway to Heathrow shows little appreciation of practicalities.

By assuming, indeed relying, on the best case scenario in many complex situations, I think that they are setting themselves up for disappointment. Much as I’d love to believe that SKYLON is the future of UK space exploration, I think it would be unwise to pin my hopes on it until there is more concrete proof that finances are in place for it to be built, let alone live up to our hopes and dreams.

Perhaps I’m too much of a cynic, but I’m always open to changing my mind. Please add your comments to this post – I’d love to know what you think.

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