Skylon ‘spaceplane economics stack up’

Skylon D1 Skylon is the result of 30 years' development and probably about 100m euros (£80m) of investment so far

It appears a feasible proposition, economically. That is the conclusion of a study that considered a European launch service based on a Skylon re-usable spaceplane.

The report, commissioned by the European Space Agency (Esa), was led by Reaction Engines Limited (REL) of Oxfordshire with help from a range of other contractors such as London Economics, QinetiQ and Thales Alenia Space (TAS).

It looked closely at how an operator of the UK-conceived vehicle might meet the demands of its market.

Those requirements would be primarily to loft big telecoms satellites high above the equator of the Earth, but also to put smaller, Earth-observing spacecraft in Sun-synchronous orbits (a type of orbit around the poles). These are the sorts of jobs the Ariane 5 rocket does today, and which Ariane 6, currently under discussion among European governments, may do from the early 2020s onwards.

Skylon is not in that discussion space at the moment - but it may get there at some point in the future if further technical studies prove positive and the financing can be found to push the concept forward.

The Skylon-based European Launch Service Operator (S-ELSO) study examined some of the hardware the vehicle would need to place satellites in orbit, and aspects of the economic model that would allow the operator to turn a profit. It even looked at how the vehicle could work out of Kourou in French Guiana - Europe's spaceport.

In all the areas the study considered, it found positive outcomes. The report was intended to provide Esa with the information it needs to help evaluate what would be a completely different way for Europe to go about its launcher business.

Skylon D1 To get telecoms satellites in position, Skylon would deploy a re-usable upper-stage propulsion unit

For starters, Skylon is nothing like the conventional rockets that Europe uses today. Skylon would operate like an aeroplane, taking off from, and returning to, a standard runway.

Ariane Traditional rockets dump exhausted boosters and propellant tanks as they ascend

Its technological trick would be its novel propulsion system - power units that work like jet engines at low altitudes and slow speeds, but then transition to full rocket mode at high altitudes and velocities in excess of five times the speed of sound.

This approach, if it can be made to work, would reduce that fraction of the vehicle's mass that must be carried as propellant, enabling the vehicle to take a practical payload to orbit in a single leap.

Although expensive to develop - think of a new Airbus design - it ought to be a good long-term investment because - again, like an Airbus - a Skylon is designed to be used over and over again. Today's rockets can be used just the once.

Indeed, the aviation model is a good one, because the idea as currently envisaged is that there would be a vehicle manufacturer (like an Airbus or a Boeing) that would sell Skylons to many operators (space equivalents of BA, Air France, Lufthansa, etc).

Skylon D1 Even though it carries a smaller fraction of propellant, its bulk is still dominated by tankage

The S-ELSO study examined whether a Skylon vehicle could handle the types of payloads governments and commercial interests are likely to want to launch over the next 20 years and more. These include the huge TV-relay, telephony and broadband satellites, the biggest of which could be eight tonnes in mass.

Skylon itself is designed only to go a few hundred km above the Earth, so it would need an additional "upper-stage" module to push the satellite into its final, 36,000km-high orbit.

For the S-ELSO study, TAS was asked to assess this piece of hardware - what it might look like and how it would perform.

It found that the module should have no difficulty putting up all the different types of telecoms satellites, including the new "electric" platforms that use solar power to do some of their own orbit raising and position-keeping.

What it did find, though, was that for the very biggest satellites (eight tonnes), the upper-stage was unlikely to be recovered. It had been an aspiration for Skylon always to try to capture the stage after it had done its job and bring it back to Earth so it too could be re-used.

In a very limited number of cases (for satellites weighing 6.4 tonnes and above), TAS says, this would not be possible. That is about one in 10 cases. In that instance, the upper-stage would be commanded just to destroy itself via re-entry into the atmosphere.

And getting satellites into Sun-synchronous orbits, where a lot of Earth-observing satellites go to picture the planet, is likely to take a different approach to traditional rockets, the study found.

Because Skylon only goes a few hundred km above the Earth, these spacecraft would have to do more of the work themselves to get into their final positions some 800km up - particularly the large ones at four tonnes or more. But with Skylon able to lift seven tonnes to the drop-off point, these satellites could be equipped with much bigger fuel tanks to complete the orbit-raising task.

The study didn't specifically assess the capability, but a Skylon should be able to loft an 11-tonne payload to the space station. It should also be able to put a probe weighing up to two tonnes on an escape path from Earth's gravity to visit other planets.

George Osborne UK Chancellor George Osborne (second left) sees the Sabre engines as a breakthrough technology

Whether Skylon ever becomes a reality depends in large part on the successful development of its Sabre engines, now in the final phase of design and demonstration with REL. To date, Esa's independent audits have found "no showstoppers".

If the hurdle is crossed - and the UK government is providing £60m to help complete the phase - then a Skylon-like vehicle ought to be producible and flying in the 2020s.

Pre cooler Engine development is in its final phase of design and demonstration

Of course, a key driver is launch prices, and the need to reduce them in order for Europe to stay competitive. Europe's current benchmark target for its next-generation launcher is 70m euros per big telecom satellite.

How much would Skylon launch prices be? That's a "how long is a piece of string?" question. Re-usability and fast turnaround for the operator obviously have a significant downward pressure on prices, but there is also an issue of initial development cost and how that is recovered.

As the S-ELSO document states: "Assuming successful development of the Skylon vehicle, it was found that the S-ELSO business could be economic in exploitation and would be very competitive against a price target of 70m euros. It would also be competitive against the 41.5m-euro price target if there is some level of public support for the Skylon vehicle development programme, which would reduce the vehicle acquisition cost to S-ELSO." (The 41.5m-euro target would be the equivalent of an American Falcon 9 launch according to current SpaceX prices.)

What this means is that Skylon manufacturing and operations could be fully commercial, but some sort of lubrication in the form of a public-private partnership is probably going to be needed.

This touches on the issue of de-risking. The more governments put in at the beginning, the more likely they are to pull in private investors and reduce the overall scale of the financial burden that needs to be recovered - through the purchase price of the spaceplanes and ultimately in the prices they demand to launch satellites.

Skylon D1 The model is an aviation one in which an operator might purchase a number of vehicles from a manufacturer
Jonathan Amos Article written by Jonathan Amos Jonathan Amos Science correspondent

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  • rate this

    Comment number 13.

    I am not sceptical - I am fearful that after the best part of 30 years development somehow or other the whitehall manderins manage to cock it up like they did with Whittle and the jet engine - leaving others (USA, Russia, China) to reap the benefits. It's funny but £60M seems a lot but on the same day Apple announce they are buying a headphone brand for over a billion.
    Cor blimey!

  • rate this

    Comment number 12.

    re. 6.gareth
    Actually it's an invention of Alan Bond and pals,,.. who just happen to be British,. and not property f the British people at large.
    They're probably going to want to market it to as many people(at least decent clients) as possible as soon as possible.

  • rate this

    Comment number 11.

    This needs to be backed by our govenment and UK plc, it can't be allowed to go the way of the jet engin, if we can control this tech and keep it UK owned, we can corner not only the space launches market but also a fair chunk of the aviation market as well.

  • rate this

    Comment number 10.

    I'll happily invest in this concept. I think that this is the next step in launcher evolution, and I just hope that the UK can derive the benefit, rather than let foreign business make money from our intellectual property.

  • rate this

    Comment number 9.

    Flying a vehicle into to space without any stage seperation and returning to earth is the holy grail of space travel and will lead to other technologies. I think we must grab this chance to put the UK, where we belong, at the forfront of engineering.

    Carpe diem.

  • rate this

    Comment number 8.

    I'm not going to lie, I still have that slight scepticism that this project will run aground.
    It's not that the science doesn't add up (it does and they even proved the engines work), it's more that I worry that no-one will fund this as much as it is needed.

    I hope the government get their finger out of their hineys and give this project the proper funds it deserves.

  • rate this

    Comment number 7.

    Well the Dan Dare concept of space travel might have the last laugh after all! Yes this should be encouraged and funded. I hope ESA Ariane interests won't scupper it. But if Sabre works it'll be more than Skylon that will fly. This report seems to indicate a willingness to progress. The sooner the better!

  • rate this

    Comment number 6.

    They need to consider looking at some kind of limited stock offering. i'd certainly be interested. This is a brilliant British invention and it needs to stay that way and we shouldn't be sold down the river like we have so many times by incompetent bureaucrats in the UK govt.

  • rate this

    Comment number 5.

    Hopefully if Reaction Engines get Skylon of the ground they won't keep it as an exclusive product and they'll market it worldwide to numerous operators/spacelines,.. this will maximize their sales and allow them to reduce unit costs, and the competition between operators would keep launch costs down.

  • rate this

    Comment number 4.

    If one of the goals is reusability wouldn't it make more sense to deploy something as a dedicated "orbital tug" to stay on orbit instead of a "final stage" that has to be brought back with each trip? The article mentions some of the new propulsion types, a dedicated orbital "transit hub" where cargos could be deployed into selected orbits after being lifted would be something to think about now

  • rate this

    Comment number 3.

    Just to put things in perspective 60 million is the prize fund for this weeks current Euro Millions lottery. That's how cheap the next phase is.. Skylon and Sabre are classic disruptive technologies. which is where, if succesful, all the really big money eventually flows from.

    So come on George get OUR chequebook out and fund REL.

  • rate this

    Comment number 2.

    This is a fantastic project - a real disruptive technology and a show case for British ingenuity.

  • rate this

    Comment number 1.

    Of all the SSTO concepts Skylon with its SABRE engines looks by far to be the most promising.
    Currently we are relying on expensive throwaway launch hardware,,.. meaning either we need to develop far cheaper(possibly pressure fed) single use rockets that are still reliable, or develop expensive hardware that can be reused constantly.


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