(failure) Hypersonic Technology Vehicle atop Minotaur on Apr 22, 2010

[Eagle]

True, but I think I mis-phrased what I was trying to say:

I don't think the hypersonic UAV would be acceptably manoeuverable at low (i.e. dogfighting) speeds (probably <Mach 1) for it to be an effective dogfighter, and if it tried to turn with a conventional fighter jet at higher speeds (especially hypersonic), it would probably break up from the stress.

Well that all depends upon the design of the craft. The AIM-12 AMRAAM is more maneuverable than a fighter jet, however it doesn't have the fuel to get its speed back up after making a turn. So pilots can be clever and maneuver in ways that force the missile to expend all of its airspeed at which point it becomes a lawn dart in some farmer's field.

Also manned fighters are limited in the number of g's they can pull more by the tolerance of the pilot than the airframe.

 

[ar81]

They better build a Delta Glider IV...
The pilot should be one of us and I bet anyone would pilot for free.
Dan Steph could be hired to make the proper software.:thumbup:

 

[SiberianTiger]

DARPA's HTV-2 Didn't Phone Home

DARPA says it lost contact with its HTV-2 hypersonic test vehicle 9min after launch of the dart-like glider atop a Minotaur IV Lite booster from Vandenberg. The agency's brief press release says the Minotaur successfully delivered its payload to the desired separation conditions and deployed the HTV-2, so telemetry was lost after the unpowered vehicle was released at the edge of the atmosphere.

One possibility is that a sheath of plasma that would form around the vehicle as it reentered the atmosphere at Mach 20-plus could have interfered with telemetry. But in an interview with Aviation Week before the flight, DARPA program manager Paul Erbland said the risk of ionized gases attentuating signals from the vehicle was "relatively modest", particulary at the high altitude the HTV-2 was deployed.

The sharp-edged, highly swept HTV-2 is designed to demonstrate long endurance at high speed by achieving an "unprecedented" hypersonic lift-to-drag ratio, much higher than the Space Shuttle's, and having a carbon-carbon aeroshell that provides thermal protection with minimal ablation, unlike a reentry-vehicle heat shield that burns off to shed heat.

Uncovered by the incomparable flateric on secretprojects.co.uk, this graphic from a December presentation by DARPA Tactical Technology Office director David Nyland suggests contact with the HTV-2 (on the yellow Mission A line) was lost somewhere between beginning reentry and starting its hypersonic glide.

Bill Sweetman wrote:
I talked to a longtime member of the hypersonic community at a conference in February, and he was fretting that the HTV-2, with sharp leading edges, was a high-risk approach. It's also the baseline for Prompt Global Strike. I expect that Boeing's alternative will be a biconic shape, more like the legendary AMaRV.

DARPA Investigates Hypersonic Glider Loss

The first mission was to be a direct flight from Vandenberg to Kwajalein, with a series of S-turns to bleed off energy and collect aerodynamic data. The second flight, set for 2011, was planned to expand the envelope to higher velocity, up to Mach 25, and demonstrate cross-range maneuvering.

A key factor in aero-thermal design is the transition from laminar to turbulent flow over the vehicle, as boundary-layer turbulence increases drag and surface heating and drives heat-shield thickness. “In the past vehicle designers assumed the whole flight was turbulent, which caused us to overdesign the heat shield and carry excess weight,” he said.

Transition prediction for previous hypersonic designs was based on correlation with existing data derived from reentry-vehicle and space shuttle flights, “[but] we didn’t have a database for slender hypersonic lighting vehicles,” Erbland said. As a result, DARPA, the U.S. Air Force and Lockheed Martin developed and used physics-based transition design tools for the first time in hypersonic vehicle development.

“We demonstrated the physical mechanisms driving transition are fundamentally different for this shape than for reentry vehicles or the shuttle,” he said. The new tools predicted transition would occur earlier than expected using correlation-based analysis, so the HTV-2 was designed to carry additional energy into each maneuver to account for increased drag. “Transition behavior is sensitive to shape change. We have developed new analysis tools to fully couple that change to the heating and feed it back into the aerodynamics.”

Autonomous guidance, navigation and control was designed to enable the HTV-2 to manage its energy and fly a precise flight path to a “very accurate” terminal location, said Erbland. After release, the vehicle was planned to navigate via a series of waypoints, managing its trajectory “to arrive with sufficient energy to get to the next one, plus a little extra in case the drag is higher than predicted.”

 

[Star Voyager]

Finally! Something that represents one of my favorite spacecraft:

 

[SiberianTiger]

http://www.defense-aerospace.com/ar...concludes-review-of-falcon-htv_2-failure.html

DARPA Concludes Review of Falcon HTV-2 Flight Anomaly


(Source: DARPA; issued November 16, 2010)


Following an extensive six-month review, the independent Engineering Review Board (ERB) chartered to examine data collected during the Falcon Hypersonic Technology Vehicle’s (HTV-2) first flight has completed its review.

The ERB concluded that the anomaly resulted from flight control authority limitations to operate at the angle of attack the vehicle was programmed to fly for the speed and altitude of the flight.

Detailed analysis conducted by the ERB revealed that the most probable cause of the HTV-2 flight anomaly was higher-than-predicted yaw, which coupled into roll thus exceeding the available control capability at the time of the anomaly. The analysis concluded that knowledge of several key aerodynamic parameters in this flight regime was limited.

According to David Neyland, DARPA Tactical Technology Office director, “The conclusions of the ERB indicate that no major changes to the vehicle or software are required to mitigate the first flight anomaly. Engineers will adjust the vehicle’s center of gravity, decrease the angle of attack flown and use the onboard reaction control system to augment the vehicle flaps when HTV-2 flies next summer.”

The first flight demonstrated significant accomplishments in the area of hypersonic flight. During the most challenging segment of flight, extensive data was captured for critical areas of interest to the program, (aerothermal, aerodynamic, thermal protection, navigation, guidance and control in the hypersonic flight regime).

This knowledge enabled the ERB to confirm: “The HTV-2 flight anomaly is characterized as a slow divergence about the longitudinal axis (in roll) which continued until the roll rate reached a threshold where the autonomous flight system commanded flight termination.” The flight also demonstrated successfully the first ever use of an autonomous flight termination system.

Additionally, the flight represented the inaugural launch of the Minotaur IV booster. The booster demonstrated the ability to fly at extreme angles of attack up to 89 degrees to meet stringent release requirements for the HTV-2.

The ERB reviewed and concurred with DARPA’s corrective approach to support the launch of a second flight in late 2011.