Hy-what? Finding it hard to keep all those hypersonics programmes straight?
After all, the US Air Force Research Laboratory's Boeing X-51A waverider, powered by Pratt & Whitney Rocketdyne's SJX61 scramjet, is the just latest in a long line. Here is a quick guide to the various recent and current research efforts aimed at air-breathing vehicles capable of speeds exceeding Mach 5.
[NOTE - I updated this on 10/15/07 and will try to keep it up to date.]
First some terminology:
A scramjet is a ramjet in which air flowing through the combustion chamber is supersonic. It can be hydrogen-fuelled, for space launch vehicles, or hydrocarbon-fuelled, for aircraft and missiles. A waverider is a vehicle that improves its lift-to-drag ratio using compression lift generated by its shockwaves. Here is a great diagram describing a scramjet-powered waverider.
First-generation scramjets have two-dimensional, or rectangular flowpaths and inlets with flat ramps that compress the airflow. Inward-turning scramjets have three-dimensional, or axisymmetric flowpaths and curved inlets that compress the airflow on all sides. They promise to be more efficient.
Hyper-X – a NASA programme that achieved the first successful flights of a scramjet-powered aircraft. Three unmanned, expendable X-43As were flown, two successfully, reaching Mach 6.83 in March 2004 and Mach 9.68 in November 2004. The X-43A was an air-launched, rocket-boosted free-flier powered by a hydrogen-fuelled scramjet. An X-43B with rocket/scramjet combined-cycle engine, a hydrocarbon-fuelled X-43C, and a hydrogen-fuelled X-43D capable of Mach 15 were all cancelled.
HyShot – a University of Queensland, Australia programme that claims the first scramjet flight to achieve supersonic combustion, in July 2002. Launched by sounding rocket on a ballistic trajectory from Woomera, the scramjet payload remained attached to the second stage. Of the five flights so far, two have achieved supersonic combustion with results of the latest, the HyCAUSE flight in June 2007, still being analysed. Australia plans more HyShot flights as part of the HIFiRE programme.
HyCAUSE – Hypersonic Collaborative Australia/US Experiment – a joint programme between Australia’s Defence Science and Technology Organisation and the US Defense Advanced Research Projects Agency to conduct the first flight test of an inward-turning scramjet. The US-supplied scramjet reached Mach 10 during the June 2007 HyShot V sounding-rocket flight from Woomera.
HIFiRE – Hypersonic International Flight Research Experimentation – a joint programme between Australia’s DSTO and the US Air Force Research Laboratory, which will involve up to 10 sounding-rocket flight tests between 2008 and 2011 from Woomera. The programme is to culminate in tests of two different free-flying waverider vehicles powered by inward-turning scramjets – one Australian and one US.
HyFly – DARPA and Office of Naval Research programme to flight test a Boeing-designed high-speed strike missile demonstrator capable of Mach 6 and 400nm range. The air-launched, hydrocarbon-fuelled HyFly has an Aerojet dual-combustor ramjet (DCR). This pre-burns liquid fuel in a subsonic ramjet to generate a fuel-rich gas that is then burned in a scramjet. The entire DCR is made of ceramic matrix composite. Two ramjet-powered flight tests are planned.
HyTECH - Hypersonic Technology - the programme started by AFRL in 1995, after cancellation of the X-30, to maintain a capability in hypersonic propulsion. Under HyTECH, Pratt & Whitney was awarded the HySET (Hypersonic Scramjet Engine Technology) contract to demonstrate a hydrocarbon-fuelled scramjet, originally for the X-43C and then the X-51A.
Hy-BoLT – Hypersonic Boundary Layer Transition – A NASA programme to gather high-speed flight data on boundary-layer transition flow physics. To be launched in summer 2008 from NASA Wallops in Virginia on ATK's ALV X-1 rocket, the chisel-shaped Hy-BoLT payload will be smooth on one side and rough on the other.
Hy-V - led by the University of Virgia and Virginia Tech, Hy-V is a project to flight test a scramjet at Mach 5 using a sounding rocket launched from NASA Wallops. There are plans for a V-Prize challenge - modelled on the X-Pize suborbital competition - for the first hypersonic vehicle capable of launching from Virginia and landing in Europe in less than an hour.
Falcon - Originally Force Application and Launch from CONUS (continental US), now just Falcon, this is a DARPA programme to demonstrate technology for a hypersonic cruise vehicle (HCV) capable of delivering a 12,000lb payload a distance of 9,000nm from the USA in 2h. Prime contractor Lockheed Martin Skunk Works is to build two unmanned, expendable HTV-2 hypersonic technology vehicles for flight tests in 2009. The unpowered HTV-2 will be boosted to Mach 20 by an Orbital Sciences Minotaur launch vehicle to demonstrate high lift/drag aerodynamics and high-temperature materials for sustained hypersonic cruise. Plans then call for a follow-on HTV-3X demonstrator, which brings us to...
Blackswift - under DARPA's Falcon programme, the Skunk Works is working on conceptual design of the HTV-3X: a reusable, unmanned hypersonic technology demonstrator with turbojet-scramjet combined-cycle engines. DARPA is seeking funding beginning in 2009 to build and fly the HTV-3X, which would be renamed the Blackswift. The demonstrator would take off conventionally and accelerate under turbojet power to around Mach 3, where the ram/scramjets take over, boosting the vehicle to a Mach 6 cruise before returning to a conventional landing. Like this...