Hypersonic Rocket-Plane Program Inches Along, Stalls
The path toward a hypersonic space plane has been a slow one, filled with twists and turns one would expect given the technological leap involved. Speeds of Mach 8+ place tremendous heat and resistance stresses on a craft. Building a vehicle that is both light enough to achieve the speeds desired at reasonable cost, and robust enough to survive those speeds, is no easy task.
Despite the considerable engineering challenges ahead, the potential of a truly hypersonic aircraft for reconnaissance, global strike/ transport, and low-cost access to near-space and space is a compelling goal on both engineering and military grounds. The question, as always, will be balancing the need for funding to prove out new designs and concepts, with risk management that ensures limited exposure if it becomes clear that the challenge is still too great. In October 2008, the US Congress decided that FALCON/Blackswift had reached those limits. That decision led to the program’s cancellation, though some activities will continue.
The FALCON Hypersonic Vehicle: Technical Challenges
The famous SR-71 Blackbird, which cruised at “only” Mach 3, made heavy use of titanium and had to use slip fits instead of rivets in many places, so that the plane wouldn’t tear itself apart when 800-900 degree surface temperatures made it expand. On the ground, and when being refueled shortly after takeoff, the plane would reportedly leak like a sieve until speed and heat had given the airframe its requisite fit.
While the state of the art has advanced since then, so have the desired speeds – and the accompanying challenges.
Making more advanced powered hypersonic aircraft work was always going to take some fancy technologies – and ongoing American interest in military initiatives like “Prompt Global Strike” may yet lead to renewed funding. Engines that can boost a plane to hypersonic speeds are very different, however, as metals tend to melt at the temperatures created by air friction at Mach 9. On Oct 8/06, journalist David Axe offered some insights, back when HTV-3 was still a live goal:
Engineers are improving on this so-called “combined cycle” to propel the Falcon, using a more powerful “scramjet” in place of the ramjet. “We need propulsion that transitions seamlessly from Mach 0 to Mach 9 or 10,” says Lockheed Martin’s Bob Baumgartner.
“For low speed, we’re looking at turbine engines that can perform at speeds from Mach 0 to Mach 4, then a scramjet … that takes over anywhere between Mach 2 and Mach 4 and goes up to higher Mach numbers — depending on the fuel, up to Mach 10,” says Steven Walker, a Darpa researcher. “For sure, we know how turbines work, but we don’t have turbines that work at Mach 4.”
“The scramjets are still at a low-technology readiness level,” he adds. “Combining both flow-paths and looking at how you transition from one to the other and the transition back … that’s all new, break-through technology.”
“Thermal protection … is the next major enabling technology,” Baumgartner says, referring to ways of coping with the high temperatures that Mach-10 flight generates. “We’re looking at durable metallic thermal protection panels to withstand heat and keep it away from structure. We’re also looking at ceramic panels.”
These technologies have uses in a variety of systems, including hypersonic missiles. That’s why research in these areas hasn’t stopped, even if HTV-3 is no longer on the planing board. “DARPA’s Hypersonic Vulcan Engine Meld” covers a program aimed at researching those kinds of advanced combined engine technologies.
The FALCON Hypersonic Vehicle: Industrial Teams
Lockheed Martin has reportedly completed conceptual design of an HTV-3X demonstrator. The are also performing subscale tests of the combined-cycle propulsion system, and have ground-tested inlets and nozzles that are shared by the high-mach turbine and the ramjet.
At this point, Lockheed Martin appears to have secured a team for the main bid that also includes Boeing and ATK.
Rolls-Royce and Williams International are developing candidates for the 13-inch diameter high-Mach jet turbine.
A round-combustor dual-mode ramjet under development by Pratt & Whitney Rocketdyne will be used as the ramjet, once the turbine has accelerated the vehicle to a high enough speed.
The FALCON Hypersonic Vehicle: Program History & Changes
The HTV (Hypersonic Technology Vehicle) became a joint program involving DARPA and the U.S. Air Force Research Laboratory. It is just one part of the broader DARPA/USAF FALCON program for lower-cost access to space. HTV-1 is part of DARPA’s larger FALCON (Force Application and Launch from Continental US) program that includes the HTV and military spaceplane efforts, and also the Small Launch Vehicle (SLV) program for cheap, responsive rocket launches. AirLaunch LLC’s innovative QuickReach C-17 based launch technology is part of the SLV program, as is SpaceX’s Falcon rockets, which have gone on to more success.
In their Jan 27/06 article “High-speed air vehicles designed for rapid global reach,” the USAF promised that:
“…in September 2007, the Falcon HTV-1 is set to complete its inaugural voyage over the Pacific Ocean. Attaining Mach 19, the vehicle will briefly exit the Earth’s atmosphere and re-enter flying between 19 and 28 miles above the planet’s surface. Demonstrating hypersonic glide technology and setting the stage for HTV-2 represent the primary focus of the lower risk, lower performance initial flight.
…For the second demonstration, scheduled for 2008 or 2009, the Falcon HTV-2 will feature a different structural design, enhanced controllability and higher risk performance factors during its high-speed journey. Like its predecessor, the system will reach Mach 22 and then finish its one-hour plus mission over the Pacific Ocean… As of January 2006, HTV-1 is beginning construction.”
According to a May 30/06 Flight International report, however, technical difficulties forced a change in schedule. DARPA and prime contractor Lockheed Martin decided not to build and fly the two planned HTV-1 craft, after subcontractor C-CAT experienced delamination problems with the curved leading edges of the carbon-based aeroshell. Instead, they have shifted efforts to a different HTV-2 design whose multi-piece aeroshell has thinner leading edges, and will be easier to build because it’s less of a technical stretch. Meanwhile, thermal protection research will continue.
As the Flight International article notes, these developments had effects on the program’s schedule:
“The change will delay a first flight from 2007 for the HTV-1, to late 2008 for the first of two ground-launched, expendable HTV-2s. These will be followed by a reusable HTV-3 closer in design to the objective hypersonic cruise vehicle (HCV). The Mach 10 HTV-3 will be unpowered, but Walker says DARPA has received funding to develop and ground test a propulsion system for the HCV.
Walker says Lockheed has selected a high-Mach turbine engine and supersonic-combustion ramjet (scramjet) for a combined-cycle powerplant enabling the HCV to take off from a runway and accelerate to a hypersonic cruise. Tests of the “inward-turning” inlet and scramjet are planned for later this year .”
HTV-3, at least, seemed to retain a great deal in common with the January 2006 USAF article’s description of a reusable Falcon vehicle:
“On the other hand, the third and final Falcon HTV, slated for 2009, will be a departure from the previous demonstrations. The reusable hypersonic glider will lift off from NASA’s Wallops Flight Facility at Wallops Island, Va., and then more than an hour later, be recovered in the Atlantic Ocean.
In addition, the HTV-3, flying at Mach 10, will be designed to achieve high aerodynamic efficiency and to validate external heat barrier panels that will be reusable.”
That proved a bridge too far, for now. In the end, HTV-3 was canceled, and FALCON flights were restricted to rocket-carried, unpowered test vehicles. There were to be 2 HTV-2 launches, in 2010 and 2011, costing about $308 million. Following the failure of the 1st such test in April 2010, the fate of the 2nd test was uncertain, but DARPA appears ready to go ahead.
FALCON Hypersonic Vehicle: Contracts & Key Events
Unless otherwise specified, all of these contracts are issued by the Defense Advanced Research Projects Agency (DARPA) to Lockheed Martin Aeronautics Co. in Palmdale, CA.
Nov 16/10: What happened to HTV-2? An independent Engineering Review Board (ERB) says the problem was more yaw than expected, which turned into a roll that was too fast for the autonomous flight control system to handle. The programmed response to that was “flight termination” via a forced roll and pitchover directly into the ocean, which is what happened 9 minutes into the 30 minute flight.
That’s the bad news. The good news is that DARPA got data from the flight covering aerothermal, aerodynamic, thermal protection, navigation, guidance and control; and now knows that the flight termination system works. DARPA TTO Director David Neyland thinks HTV needs tweaks rather than a full redesign, and wants to repeat the test in late 2011, after adjusting the vehicle’s center of gravity, decreasing its angle of attack (nose-up angle), and augmenting the flaps with the onboard reaction control system. Defense Update | Washington Times.
April 26/10: “Team Vandenberg launched the first Minotaur IV Lite launch vehicle at 4 p.m. April 22 from Space Launch Complex-8 here. The rocket launched the Defense Advanced Research Projects Agency’s Falcon Hypersonic Technology Vehicle 2. The 30th Space Wing commander, Col. David Buck, was the launch decision authority.”
Unfortunately, a DARPA statement said that:
“The launch vehicle executed first-of-its-kind energy management maneuvers, clamshell payload fairing release and HTV-2 deployment… Approximately 9 minutes into the mission, telemetry assets experienced a loss of signal from the HTV-2. An engineering team is reviewing available data to understand this event.”
Aviation Week adds that:
“Based on a mission timeline released by DARPA in December, the HTV-2 was between beginning reentry and starting its hypersonic glide when telemetry signals were lost.”
Feb 18/10: US FedBizOpps, opportunity #N00033-10-R-2008:
“This requirement is for the charter of one (1) US flag vessel. The period of performance, if all option periods are exercised, is estimated to be approximately 29 days. The firm period will commence on 03 April 2010, lasting for 21 days. In addition, there will be three (3) 3-day options periods. Vessel is required to provide a variety of terminal impact area support functions to an experimental Hypersonic Technology Vehicle (HTV-2) flight test that is part of the DARPA-USAF Falcon Program. The HTV-2 will be launched on a booster from Vandenberg AFB, CA to an impact near the Reagan Test Site (RTS), Kwajalein Atoll in the Marshall Islands. A launch date is planned to occur within an 8-day window lasting from April 20 through April 27, 2010. The vessel will be required to operate in close proximity to the RTS. The primary activities supported in the impact area will be (1) to transport, deploy and retrieve a set of nine impact scoring rafts, along with two Telemetry Buoys and (2) to obtain telemetry from the HTV-2 in its final seconds of flight all the way to impact from a vessel standoff distance of approximately 10 nm.”
This upcoming test is supposed to demonstrate HTV-2’s ability to withstand hypersonic heat buildup, and remain controllable. The launch rocket is expected to be a Minotaur IV Lite. FBO solicitation | WIRED Danger Room.
Oct 13/08: DARPA cancels the Blackswift reusable hypersonic testbed, after a skeptical Congress slashed the program’s FY 2009 budget from $120 – 10 million, cutting DARPA funding from $70 – 10 million and eliminating the Air Force’s requested $50 million entirely.
DARPA says it will continue with the Falcon program by flying unpowered hypersonic test vehicles in 2009, launched by Orbital Sciences Minotaur boosters in order to demonstrate their aerodynamic and structural technologies.
DARPA had hoped to award a contract for the demonstrator later in 2008, and was believed to be negotiating with a Lockheed Martin Skunk Works-led team that included Boeing. The Blackswift was expected to fly in 2012. Defense Technology International | Flight International.
July 25/08: Aviation Week’s Aerospace Daily & Defense Report reports that ATK and Boeing have joined Lockheed Martin’s “Blackswift” team for the FALCON HTV project, adding that Northrop Grumman has declined to bid.
If the reports are true, this would make it very difficult to field a credible competing team from American industry.
March 13/08: DARPA Director Dr. Tony Tether discusses FALCON during congressional testimony before the House Armed Services Subcommittee on Terrorism, Unconventional Threats and Capabilities [PDF]:
“When the U.S. Decides to act, we envision using new hypersonic vehicles to quickly reach any point on earth without the need to organize an air refueling tanker fleet to support a long-range mission. With this vision in mind, DARPA’s Falcon program has been working to vastly improve the U.S capability to promptly reach other points on the globe. A major goal of the program is to flight test key hypersonic cruise vehicle technologies in a realistic flight environment. Recently we conducted both low- and high-speed wind tunnel tests that validate the stability and control of the hypersonic technology vehicle across the flight regime. The program is also developing a vehicle test bed called Blackswift. By the end of 2012, our goal is for Blackswift to take off under its own turbojet power from a runway, accelerate to Mach 6 under combined turbojet/scramjet propulsion, and land on a runway.”
Dec 14/07: A $6 million increment of a $40.8 million modification to a previously awarded “other transaction for prototypes agreement,” as part of the Falcon HTV program’s Phase 3.
Phase 3 will include fabrication and assembly of 2 hypersonic technology vehicles to be flight-tested during 2009. Work will be performed in Palmdale, CA (9%), King of Prussia, PA (79%), and Fort Worth, TX (12%), and is expected to be completed in December 2009. Funds will expire at the end of the current fiscal year. This is a sole source award (HR0011-04-9-0010/P00032).
April 10/07: A $10.2 million modification to a previously awarded other transaction for prototypes agreement to exercise an option for the Falcon Combined Cycle Engine Technology portion of the Falcon Hypersonic Technology Vehicle effort.
Work will be performed in Palmdale, CA (20%); Philadelphia, PA (73%); and Fort Worth, TX (7%), and is expected to be complete in September 2008 (HR0011-04-9-0010, P00027).
Oct 25/06: A $33.2 million modification to a previously awarded other transaction for prototypes agreement, to continue development and demonstration of the Hypersonic Technology Vehicle portion of the Falcon program. Work will be performed in Palmdale (20%), Philadelphia, PA (73%), and Fort Worth, TX (7%), and is expected to be completed in September 2008. This agreement is incrementally funded, and this is a sole source award (HR0011-04-9-0010/P00022).
Aug 22/06: A $14.6 million modification exercises options for prototypes, as part of an agreement to continue development and demonstration of the hypersonic technology vehicle portion of the FALCON program. Work will be complete in September 2008. This Agreement is incrementally funded; no funds are being obligated at this time (HR0011-04-9-0010/P00021).
March 3/06: The University of Dayton Research Institute in Dayton, OH received a $9.9 million cost plus fixed fee contract to research heat protection for hypersonic vehicles. Solicitations began in December 2005, and negotiations were complete in February 2006. The Headquarters Air Force Research Laboratory, Wright-Patterson Air Force Base, issued the contract (FA8650-06-C-7615). As the DefenseLINK release notes:
“The Air Vehicles directorate has for several years conducted focused research on high temperature thermal protection systems that support high-speed air vehicles. The primary application of this technology is to un-powered hypersonic technology vehicles such as those being developed in the DARPA/AFSPC Falcon Program. However, this technology has many other applications to high-speed air, re-entry and space access vehicles. Ongoing research into these thermal protection systems is approximately half complete; this effort will carry the research through to completion over the next five years.”
June 27/05: An $8.9 million increment of a $19.9 million modification to a previously awarded other transaction for prototypes agreement. It exercises two options to continue development and demonstration of the hypersonic technology vehicle portion of the Falcon program. Work will be performed in Palmdale, CA and will be complete in September 2008. $2 million will expire at the end of FY 2005 (HR0011-04-9-0010).
March 16/05: A $10.6 million increment toward the DARPA/USAF FALCON program. The increment is part of a $55.2 million modification that exercises the option for Phase IIb of Task 2 (Hypersonic Technology Vehicle). Work will be performed in Palmdale, CA (41.5%) and King of Prussia, PA (58.5%) and will be completed in December 2005. $3 million of these funds will expire at the end of FY 2005 (HR0011-04-9-0010, P00006).
Aug 6/04: A $7.6 million increment of an $8.4 million other transaction for prototypes agreement. It covers Phase IIa of Task 2 (hypersonic technology vehicle) of the DARPA/Air Force Falcon program. Work will be performed in Palmdale, CA (41.5%) and King of Prussia, PA (58.5%) and will be complete in February 2005. $4.6 million of the funds will expire at the end of FY 2004. This was a limited competition among the 4 participants in Phase I of the Falcon HTV program (HR0011-04-9-0010).
Additional Readings & Sources
- DARPA – FALCON Program
- Globalsecurity.org – Military Spaceplane. See also the subsidiary page Hypersonic Technology Vehicle (HTV)
- Globalsecurity.org – X-51 Scramjet Engine Demonstrator – WaveRider (SED-WR)
- ONERA – Ramjet, Scramjet & PDE: An Introduction
- DID – DARPA’s Hypersonic Vulcan Engine Meld
- DID Spotlight – Australia, USA Collaborating on Hypersonic Research (updated). Details the $54 million HIFiRE program, which is making significant contributions to hypersonics research.
- CDI (Sept 26/06) – The future is coming – will we notice the difference? Good companion to the ONERA piece; actually a long look at the details and challenges of ramjet and scramjet technologies, and current research, all written in an accessible style if you can filter for political content.
- Defense Tech (Oct 18/06) – Falcon Fills Blackbird’s Shoes
- Flight International (Aug 29/06) – Hyper activity: Hypersonics research in the USA. Includes details re: HTV, and many related projects that are advancing hypersonic technologies.
- Flight International (May 30/06) – US hypersonic aircraft projects face change as Congress urges joint technology office
- USAF News (Jan 27/06) – High-speed air vehicles designed for rapid global reach
- Talking Proud – The Falcon is coming, hypersonic attack from the US