FI: Hyper Activity

Flight International has a fairly accurate picture of the hypersonic research currently in work, including HyFly. There are some interesting programs out there, and hopefully the research will succeed. We could use some success in our research efforts.

Hyper Activity
After test hits and flops, budget ups and downs, is US hypersonic propulsion development heading for oblivion or will a rallying call reinvigorate research?

Flight International 08/01/05

When NASA's diminutiveX-43A hypersonic demonstrator streaked across the skies over the Pacific at just under Mach 10 on 16 November 2004 it was hailed as a massive success for the agency and its Hyper-X partners.

Yet, as with so many other areas of US aeronautics research, the funding for the next stage of the effort - the larger X-43C - had already been withdrawn, and as the last demonstrator plunged to a watery grave in the ocean it seemed NASA's entire hypersonic programme might soon follow it into oblivion.

The Hyper-X effort was aimed at demonstrating airframe-integrated "air-breathing" engine technologies that have the potential to dramatically increase payload capacity for reusable space launchers and hypersonic aircraft. Hyper-X was originally intended to include two additional X-43 variants beyond the -43A, of which there were three individual test vehicles.
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The 27 March 2004 flight, when the vehicle reached Mach 6.94 at 95,000ft (29,000m), and the Mach 9.68 flight the following November were therefore crucial achievements for the US hypersonic community. Thanks to these successes, the US Congress belatedly added $25 million to the NASA 2005 budget to continue low-level development work on the X-43C research vehicle.
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So what does the roadmap contain and, other than RATTLRS, what are the main programmes under the NAI umbrella?

US NAVY/DARPA HYFLY A joint effort involving DARPA, the US Navy, Boeing and Aerojet, the HyFly programme is on the verge of a series of flight tests that are to run from early 2006 to around mid-2007. Also aimed at demonstrating key enabling technologies for a high-speed tactical strike weapon capable of sustained efficient cruise at M6, the concept is based around a rocket-boosted ramjet-scramjet. Also known as a dual combustion ramjet, the ramjet element of the engine provides a "pilot", or
combustion source, for the scamjet combustor.

This is believed to be a lower-risk solution as it has a lower Mach number (M3.3) at which the engine can be started than a pure scramjet. Ground tests have shown operability over the M3.5-6.5 speed range. Eight flight tests are scheduled, two to be half-scale, short-duration flying engines at altitudes simulating full-scale engine operating conditions.

The other six will be full-scale engines used to test high-temperature treatments in the airframe (titanium) and engine (ceramics). For potential space access, the HyFly concept would be adapted to couple the scramjet with a turbine engine in a combined-cycle system. Tests conducted in 2003 in the Arnold Engineering Development Center's
aerodynamic propulsion test unit marked the first time a fully integrated hypersonic cruise missile engine using conventional liquid-hydrocarbon fuel was tested at critical flight takeover conditions.

Invention of the HyFly dual-combustion ramjet engine is credited to the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland.

USAF/DARPA SED The scramjet engine demonstration (SED) programme involves Pratt & Whitney and Boeing, and is a descendent of several previous efforts including the Affordable Rapid Response Missile Demonstration and the liquid hydrocarbon-fuelled scramjet engine developed under the USAF's HyTech programme. "The success of these two led us to press on the SED," says P&W Space Propulsion hypersonic
and combined- cycle programmes manager Joaquin Castro. "It's not a missile, but a propulsion demonstrator intended to validate the operation and performance of a scramjet engine in an operating environment as close as possible to reality. We're looking for data on acceleration and cruise performance, as well as evaluating its potential application for a strike weapon, global reach and even access to space."

Ground tests of SED are due to begin by mid-2006, with flight tests running from 2008 into 2009. "We will fly for minutes, not seconds," says Castro. "When you come to put a real system into tests you have to run it over hours. Running something for milliseconds or seconds doesn't cut it. We're going to have to go out and flight test - there's simply no substitute."

Flight tests are set to culminate in a series of sorties in which a vehicle, powered by the actively fuel-cooled SED research engine, will be boosted from around M4.5 to speeds in excess of M6.5.

DARPA/USAF FALCON The DARPA/ Lockheed Martin Falcon programme (Force Application and Launch from Continental United States), announced in 2003, is aimed at developing a range of enabling technologies to support the development and test of a range of fast-reaction, global-reach, hypersonic vehicles. High-speed propulsion and integration of the propulsion system forms only two parts of the entire effort, which is scheduled to test and produce a range of small launch vehicles as well
as a series of hypersonic test vehicles (HTV).

The goal is to demonstrate technology for a 2025-timeframe hypersonic cruise vehicle (HCV) capable of striking targets up to 17,000km (9,000nm) from the USA in under 2h. Lockheed is designing the HCV, with Aerojet working on the engine, which features an "inward-turning" flowpath. This means the inlet focuses the flow towards the centre of the engine, which has a circular cross-section. The flowpath is
therefore three-dimensional, instead of the rectangular two-dimensional cross-section of all previous hypersonic designs. The round engine has reduced internal surface area with better pressure recovery and less frictional heating. Ground tests of the flowpath are being undertaken at Calspan-University of Buffalo Research Center.

Lockheed's dual-scramjet, waverider HCV is an unmanned, reusable vehicle designed to take off from a runway and cruise at M10 and 130,000ft, carrying a 5,400kg (12,000lb) weapons payload. Three unpowered, rocket-launched HTVs are planned: HTV-1, to fly around 2007, is an expendable vehicle with an 800s flight time at M10 and two expendable HTV-2s with 45min flight time are set to be followed in 2009 by three
flights of two recoverable, reusable HTV-3s.

USAF HYTECH Forming the fundamental platform for all air force hypersonic efforts, the Hypersonic Technology (HyTech) programme has been consistently focused on the development of endothermic hydrocarbon fuel-cooled ground demonstrator scramjets with P&W.

Tests of the Ground Demonstration Engine (GDE-I) in 2003 helped develop technologies that supported NASA's Hyper-X programme and are incorporated into the follow-on SED effort. HyTech continues in support of SED, as well as tests of a variable-geometry GDE-II that could power a revived X-43C. Tests of the P&W-developed GDE-II are to take place in a NASA Langley windtunnel in 2006. "This engine will be a workhorse,
and should be able to run a number of times because we've put enough coatings on it to make it reusable. We're confined to about 1min of run time because of the limitations of the test facility," says Castro.

USAF/DARPA HISTED The USAF/DARPA high-speed turbine engine demonstration (HiSTED) is aimed at development of technologies for an M4-plus expendable turbine engine for tactical weapons and for a reusable TBCC engine. The combined-cycle application would be used for accelerating a flight vehicle to M4 plus, and would be integrated with a M4-7 hydrocarbon scramjet engine for hypersonic cruise vehicles as well as
for access to space. Phase 2 ground tests are planned around late 2007 and late 2009, with Phase II focusing on development of the TBCC version. HiSTED, with SED, forms one of two funded propulsion concepts being pursued with the Falcon programme.

DARPA HYCAUSE The US-Australian Hypersonic Collaborative Australia/United States Experiment (HyCAUSE) is a joint effort by university-based scramjet propulsion specialists in the two countries and is a follow-on to the University of Queensland's HyShot scramjet flight in July 2002, which achieved supersonic combustion in flight for the first time. Flight tests at M10 of an "inward-turning" scramjet on a sounding rocket are planned for November from Woomera in South
Australia. Lessons learned from the HyCAUSE tests are expected to feed into the Falcon conceptual vehicle design.

US ARMY HYPERSONIC ENGINE TECHNOLOGY DEMONSTRATION PROGRAMME The US Army is studying scramjet engine concepts for a M10-12 hydrogen-fuelled vehicle. Advanced features under evaluation include enhanced mixing of the fuel and air streams, cooling of the engine flowpath, drag reduction in the engine itself and boundary layer control in the engine flowpath. Component selection is due in 2007. A flowpath configuration will be decided in 2008 and the development of a flight weight engine in 2009.

Inward-turning inlet configurations, multiple flowpaths and multi-cycle ramjet/scramjet configurations are also being studied by Alliant Techsystems' GASL unit, the hypersonic propulsion specialist that built the successful engine used by the X-43A. Through funds awarded to this company, NASA has effectively kept the X-43C effort alive and both groups are now working with Boeing on potentially reviving the effort in the near term.

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