DARPA: You didn't think we could make a Mach 6 spaceplane, so let us have this MACH TEN job

Cheap rockets? Bah! Give us a hyper-hydrocarbo-scramjet

Build a business case: developing custom apps

In this post-Space Shuttle world, it often seems that the dream of a spacecraft which could reach orbit without expensively throwing most of itself away is receding rather than drawing closer.

Last time DARPA went for a spaceplane - the X-30 SSTO concept of 1984

Sure, there's the tiny X-37B "space warplane", carrying out secret missions for the US Air Force, but this takes off atop a conventional throwaway rocket stack much bigger than itself. Yes, there's the British "Skylon" plan for a completely reusable runway-takeoff spacecraft, but its backers admit that it will cost at least £10bn to develop and the scheme has been around in one form or another since the 1980s – it seems unlikely to turn up soon.

There's also internet zillionaire Elon Musk and his rather different plan, under which fairly conventional rocket stages would come down to land vertically on a pad after hurling their payloads into the sky: but while the "Grasshopper" project has demonstrated that rockets can set down vertically without problems, it has not shown that the launch stack can spare enough fuel for this to happen and still do its job cost-effectively. Certainly, at the moment Musk's rockets mostly destroy themselves on actual use, just like any others.

So it might seem to many observers that the dream of re-usable, affordable access to space for the human race remains as far off as ever.

Detail on the X-37B's wings. Credit: USAF

Something like this - but we want the rocket ON TOP of the plane

As ever, however, the Pentagon's applecart-bothering boffinry bureau DARPA would like to change things. The wild-hare war brainiacs already have a cunning scheme for a Mach-20 hypersonic rocket glider, though this wouldn't be especially re-usable - it's expected to launch atop a throwaway stack.

This week, however, DARPA lobbed out an announcement that they also aim to build a machine they refer to as "Experimental Spaceplane One" (XS-1). This rather reverses the usual pattern in which spaceplanes are fired into space by a big rocket, as seen with the space shuttle, X-37B etc. Instead, the XS-1 spaceplane will act as the first stage, hurling a rocket upper stage into the upper atmosphere at no less than Mach 10. The rocket will then carry on to deliver a payload into orbit while the "aircraft like" XS-1 returns to Earth and flies again.

The XS-1 programme is also expected to deliver:

Reusable, long-life, high thrust-to-weight, and affordable propulsion systems

Which would appear to indicate a return to the scramjet arena for DARPA. Ordinary ramjets top out at between Mach 3 and 4 due to the need to slow down the rush of air through the combustion chamber below the speed of sound, so for full-on hypersonics one needs a supersonic-combustion job (eg a scramjet).

Hydrogen-fuelled scramjets have hit the XS-1 target speed of Mach 10 in tests, but hydrogen fuel is out of fashion among the trendy kids these days due to the great expense and difficulty of using it – though NASA still intend to use in their upcoming SLS mega-rocket, and the Skylon chaps think it's OK. Elon Musk favours kerosene in his new rockets, and DARPA and other US military labs have been struggling for years to get scramjets to run on more conventional hydrocarbon fuels. The XS-1 is intended to demonstrate "operations dramatically reducing infrastructure and manpower requirements while enabling flight from a wide range of locations", so it's plain that this is still the aspiration.

The various hydrocarbo-scramjet trials to date have had a spotty test record, to put it mildly, but the US Air Force's final X-51 Waverider test shot is said to have achieved sustained Mach 5 flight on relatively normal JP-7 juice. Perhaps this can be built on to achieve Mach 10 in the XS-1.

Boost IT visibility and business value

More from The Register

next story
Just TWO climate committee MPs contradict IPCC: The two with SCIENCE degrees
'Greenhouse effect is real, but as for the rest of it ...'
Asteroid's DINO KILLING SPREE just bad luck – boffins
Sauricide WASN'T inevitable, reckon scientists
Brit amateur payload set to complete full circle around PLANET EARTH
Ultralight solar radio tracker in glorious 25,000km almost-space odyssey
Boffins spot weirder quantum capers as neutrons take the high road, spin takes the low
Cheshire cat effect see neutrons and their properties walk different paths
NASA Mars rover FINALLY equals 1973 Soviet benchmark
Yet to surpass ancient Greek one, however
Famous 'Dish' radio telescope to be emptied in budget crisis: CSIRO
Radio astronomy suffering to protect Square Kilometre Array
prev story


Implementing global e-invoicing with guaranteed legal certainty
Explaining the role local tax compliance plays in successful supply chain management and e-business and how leading global brands are addressing this.
Boost IT visibility and business value
How building a great service catalog relieves pressure points and demonstrates the value of IT service management.
Why and how to choose the right cloud vendor
The benefits of cloud-based storage in your processes. Eliminate onsite, disk-based backup and archiving in favor of cloud-based data protection.
The Essential Guide to IT Transformation
ServiceNow discusses three IT transformations that can help CIO's automate IT services to transform IT and the enterprise.
Maximize storage efficiency across the enterprise
The HP StoreOnce backup solution offers highly flexible, centrally managed, and highly efficient data protection for any enterprise.