5-Year Flights? Enter DARPA's Vulture

Vulture concept
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Three teams have now received Phase 1 contracts to begin developing develop a radical new aircraft, under a US Defense Advanced Research Projects Agency (DARPA) program known as "Vulture."

DARPA's goals for Vulture are not trivial: 5 years on station with a 450kg/ 1,000lb payload, 5kW of onboard power, and sufficient loiter speed to stay on station for 99% of the time against winds encountered at 60,000-90,000 feet. The system could act as a satellite substitute for communications relay or reconnaissance, as long as the payload fit within the weight limit. Vulture would be more vulnerable to anti-aircraft missiles than a satellite, and could be targeted by fighter jets as well given the right launch profile; on the other hand, that closeness would improve sensor resolution and communications capability.

The engineering challenges ahead are formidable, as one would expect for a DARPA project. The power system in particular must be extremely reliable, and the aircraft's materials will require advances of their own. Odysseus will be exposed to far more warming and cooling than satellites, and more ultraviolet radiation which will affect the aircraft's materials. The design is also likely to require very large wings, both to help keep it aloft and to accommodate the number of solar cells required. Conditions at altitude can challenge the durability of those wings, especially with hydrogen storage tanks attached. Aerovironment's Helios (1998-2003) demonstrated this the hard way in its 2003 crash.

So, who is competing, and what are the proposed designs?

The Process, The Designers & The Designs

AV's Helios
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If Vulture reached its goals, it would become a very potent lower-cost competitor to the USA's $20+ billion TSAT satellite program. DARPA projects aren't like normal military system development projects, however, and have different goals. Several breakthroughs will be required for complete success, but even 1-2 breakthroughs in areas like materials durability at 60,000-90,000 feet will deliver advantages that can be carried over to other programs - such as the High Altitude Airship.

During Vulture's Phase 1 conceptual system definition (12 months, 2008-2009), the firms will define their aircraft, run formal reliability and mission success analysis, and blueprint full-scale and subscale demonstrators. Phase 1 concludes with a System Requirements Review

The Phase 2 risk reduction development and testing phase (2009 - mid-2012) go-ahead would build and testing a subscale demonstrators capable of flying for 3 months, and would end with an uninterrupted 3-month system flight demonstration.

Phase 3 fabrication would involve a full-scale aircraft demonstrator capable of staying up for 12 months, a flight test for 12 uninterrupted months, and a program that reaches a Technology Readiness Level standard of TRL 6 overall. This would let Vulture enter System Design & Development as a program of record, if the military wished to field a design.

H.G. Wells' revenge:
AFS' Mars Flyer
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DARPA contract winner Aurora Flight Science is involved in building Northrop Grumman's high-altitude Global Hawk UAV, has worked on a "Mars Flyer"/ARES vehicle for NASA, and is also collaborating with Boeing and with General Dynamics on the hydrogen fuel cell powered, high altitude Orion HALL.

Aurora's winning design is called "Odysseus," using solar energy to power the aircraft during daylight, and stored solar energy to power the aircraft at night. In selecting Aurora's Odysseus, DARPA appears to have chosen a single ultra-reliable system rather than a "modular shuttling" approach, and a solar thermal approach that also uses fuel cells and has a "refuel on station" option.

Aurora's teammates on the program include BAE Systems (payloads, sensors, and concept of operations and employment); C.S. Draper Laboratories (extremely high reliability electronics and control systems), and Sierra Nevada Corporation (specialist in autonomous refueling systems).

DARPA contract winner Boeing also has a varied team drawn from inside and outside the company. Boeing Integrated Defense Systems (IDS) Advanced Systems, IDS Space and Intelligence Systems, Boeing Spectrolab and Boeing Phantom Works are all involved. Their major partner is the British firm QinetiQ, whose solar-powered, carbon-fiber Zephyr high-altitude, long-endurance unmanned aerial system is currently flying under a joint Beitish-American program. Other partners include Versa Power Systems and C.S. Draper Laboratories.

Zephyr is an ultra-lightweight carbon-fibre aircraft with a wingspan of up to 18 meters/ 59 feet, but weighing just 30 kg/ 66 pounds. By day it flies on solar power generated by amorphous silicon arrays on the wings that are no thicker than sheets of paper. By night it is powered by rechargeable lithium-sulphur batteries that are recharged during the day using solar power. Many of its design approaches and technologies will be leveraged for Vulture.

The third competitor is Lockheed Martin. Details regarding their proposal and team are not available yet.

Other award competitors were not mentioned, but Aerovironment builds the hydrogen powered Global Observer with its 1 week flight times, and has considerable experience with very advanced high-altitude solar UAVs like the Pathfinder Plus and the record-setting Helios.

The Awards

Zephyr Flight
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April 21/08: Lockheed Martin is the 3rd firm to receive funding under the Vulture program. DARPA release [PDF]

April 21/08: Boeing announces a $3.8 million contract for Phase 1 of DARPA's Vulture program. See above for details.

April 14/08: Aurora Flight Sciences announces an unspecified contract under DARPA's Vulture program. See above for details.

Sept 10/07: QinetiQ's Zephyr High Altitude Long Endurance (HALE) Unmanned Aerial Vehicle (UAV) breaks the official world record time for the longest duration unmanned flight, soaring for 54 hours to a maximum altitude of 58,355 feet over White Sands Missile Range in New Mexico. The current official FAI world record for unmanned flight was set by Northrop Grumman's RQ-4A Global Hawk on March 22/01 at 30 hours 24 minutes - and since no FAI officials were present at White Sands, that record may stand.

New technologies tested on this Zephyr flifght included solar arrays supplied by United Solar Ovonic, a full flight-set of Sion Power batteries, and a novel solar-charger and bespoke autopilot developed by QinetiQ. QinetiQ release.

Additional Readings

• DARPA TTO - Vulture. See also the May 16/07 FedBizOpps solicitation #SN07-38.

• QinetiQ - High altitude long endurance UAV - Zephyr

• Aurora Flight Sciences (April 14/08) - DARPA Selects Aurora for Vulture Program

• Flight International (March 3/08) - DARPA pushes limits of unmanned aircraft capability to extremes

• US Dept. of Energy (Sept 8/04) - NASA Releases Report on Crash of Helios Solar Plane