Graham Warwick/WASHINGTON DC
Four US manufacturers have embarked on a programme to determine. by 2005, whether unmanned combat air vehicles (UCAVs) have the potential to complement, and ultimately compete against, manned strike aircraft. If successful, UCAVs could become operational as early as 2015, in time to help offset the expected drop in the US Air Force's combat fleet as today's fighters are retired in large numbers.
Whether UCAVs are even technically feasible, let alone operationally effective, has yet to be determined, however. That is the aim of the US Defence Advanced Research Projects Agency's (DARPA) UCAV advanced technology demonstration (ATD). Boeing, Lockheed Martin, Northrop Grumman and Raytheon Systems were each awarded 10-month contracts in late April for Phase 1 of the ATD, and one team is to be selected in early 1999 to build and flight test, in 2002, a UCAV demonstrator system, including two air vehicles.
In DARPA's vision, UCAVs would go in ahead of manned strike aircraft to knock out enemy air defences, then stay around to suppress any threats that pop up during the attack. Thereafter, loitering UCAVs would maintain "persistent vigilance" over the battlefield, to keep air defences suppressed and provide an immediate strike capability against high-value and time-critical targets.
This "force enabler" mission - suppression of enemy air defences (SEAD) and deep strike in support of manned aircraft - has been chosen for the ATD because it is identifiable and achievable, and because DARPA believes that a demonstration of this role will answer fundamental technical questions about the use of UCAVs for other missions, including as an eventual alternative to manned aircraft.
Certainly demonstrating the SEAD/strike mission involves addressing the key issues of UCAV operation, including:
how to operate manned and unmanned aircraft together as part of an integrated force; how to operate safely in civilian airspace, including recovery with unexpended ordnance; how to allocate functions between the mission control station and air vehicle; how to maintain the situational awareness required for authorisation of weapon release.By requiring contractors to develop a UCAV operational system concept (OSC), DARPA is forcing them to tackle the first and biggest question: how will these systems be used? Based on their OSC, each team will then define a UCAV operational system (UOS) capable of performing the post-2010 SEAD/strike mission. This first phase of the ATD will involve exhaustive trade studies in a bid to find the optimum balance of mission effectiveness and affordability.
Definition of the UOS is intended to allow contractors to identify those technologies that must be incorporated into the UCAV demonstrator system (UDS) for flight testing during Phase 2 of the ATD. "The UOS will not be defined to the design level of a traditional acquisition programme, but in sufficient detail to be used as the primary filter for selecting critical technologies for demonstration in Phase 2," says DARPA.
Adequate definition of the UOS is important because contractors are required, as part of Phase 1, to provide a UCAV transition plan outlining the work required following the demonstration to prepare for an engineering and manufacturing development (EMD) programme, beginning as early as 2005. This plan will include a risk reduction and operational evaluation phase leading into EMD.
DARPA is promoting the UCAV ATD as a model for future technology demonstrations. Few requirements have been placed on the contractors; essentially the government has outlined the "what" and left industry to decide the "how". The agency has made it clear that it is "...not interested in an ATD programme which follows an evolutionary path from manned aircraft to a UCAV weapon system."
Although some manufacturers have proposed modifying existing fighters to demonstrate aspects of UCAV operation, DARPA believes that removing the pilot "-opens up the design space, allows creative integration of technologies and tactics and enables a revolutionary advance in affordable airpower". Only an all-new design will be able to demonstrate the benefits foreseen for UCAVs, DARPA argues - and industry agrees.
Designing a UCAV system from the ground up greatly increases the task facing contractors and, although the demonstrator will not incorporate all the features of an operational system, the programme will culminate in an end-to-end demonstration of the SEAD/strike mission involving all three key elements: control station, communications network and air vehicle.
This high-risk approach is necessary, DARPA maintains, "...to determine whether it is technical feasibility and fiscally prudent to continue UCAV development for post-2010 missions". That determination is essential, the agency argues, if UCAVs are to compete effectively against manned aircraft and cruise missiles in decisions on the future force structure.
Studies addressing the mix of manned versus unmanned aircraft are under way already in the USA, UK and elsewhere, but industry believes UCAVs will not be considered seriously until programmes like DARPA's ATD have demonstrated that such vehicles can compete with other potential solutions on cost, capability, reliability and suitability.
AFFORDABILITY DRIVER
Inevitably, affordability is a driver behind the desire to demonstrate that UCAVs can be operationally effective. DARPA is projecting an air vehicle unit cost less than one-third that of a Joint Strike Fighter (JSF), with reductions in operating and support costs of up to 80% compared those of current fighter squadrons. Not only will a pilotless aircraft be smaller and cheaper, but it will be flown less and require less maintenance, the agency believes.
In an environment that is increasingly conscious of costs and averse to losses, commanders are having to choose between manned aircraft and cruise missiles when planning attacks, and UCAVs will offer another option, Lockheed Martin says. The company calculates that the fighter-delivered precision-guided munition is the cheapest option until the stand-off range required for survival increases to the point where the cruise missile becomes the least expensive approach.
Cruise missiles are the only option when crew loss or capture is unacceptable, but they lack the flexibility of manned aircraft and incur the risk of collateral damage. UCAVs, proponents argue, offer an alternative. They can meet the same requirements for weapons authorisation as manned aircraft without putting crews at risk, yet offer a cost per target that potentially is lower than that for either fighters or missiles.
Whether those cost savings can be achieved depends largely on the concept of operations and only in part on the air vehicle design. For its UCAV ATD, for example, DARPA has not set a unit flyaway price target, but is treating life-cycle cost as a technical requirement. This reflects the fact that most savings are expected to accrue from how the UCAV is operated.
It is being left to contractors, for example, to decide how many systems are needed - a large number of cheap vehicles or a smaller number of more expensive aircraft. This determines, among other things, the level of air vehicle survivability required. Deciding what rate of attrition is acceptable is a key element of the UCAV operational system design process.
Lockheed Martin has produced cost comparison which attempt to quantify what would be an acceptable attrition rate for UCAVs. To be cost-competitive with a $20 million fighter having an attrition rate of 40,000h/mishap, a $5 million UCAV could be designed for 2,000h/-mishap, but a $20 million vehicle would have to be designed for 8,000h/mishap. As a typical attrition rate for today's unmanned air vehicles is around 500h/mishap, the challenge facing UCAV designers is obvious.
Among issues to be addressed is the degree to while the UCAV itself will be vulnerable to attack. At least in the near term, Lockheed Martin says, UCAVs "-probably will be vulnerable to manned fighters within visual range. Beyond visual range there is not technical reason to believe that a UCAV could not hold its own against a manned fighter. In the longer term, it is conceivable that technology could even make it formidable within visual range".
The SEAD/strike UCAV will be a stealthy vehicle, one reason why DARPA restricted the ATD competition to four prime contractors, three of which have known stealth experience. While survivability analysis will be a critical aspect of the UCAV operational system design phase, demonstration of low-observable and self-defence technologies is not a primary objective of the programme, DARPA says.
Instead, the UCAV demonstrators are required to be compatible with the survivability features described in the UOS. Structural layout and surface characteristics must allow for the later addition of reduced-signature materials and treatments. As now planned, one of the two UCAV demonstrators will be modified, or a third vehicle built, to incorporate the low-observable and self-defence features for flight testing during the follow-on risk reduction and operational evaluation phase.
NOTIONAL CONCEPT
While design of the SEAD/strike UCAV system is being left to the contractors, DARPA has offered a notional concept for both the operational and demonstrator air vehicles. The UOS vehicle described is a two-axis-unstable aircraft with no vertical tail, thrust-vectoring and fly-by-light flight controls using electric actuators. These elements are expected to be demonstrated in the UDS vehicle, which is required to have the same aerodynamic/propulsion integration, payload/range characteristics, sensors and weapons as the UOS aircraft.
According to DARPA, a SEAD/strike UCAV is likely to have an empty weight of 3,600kg or less and a payload of 900kg or less - typically two 450kg Joint Direct Attack Munitions or eight 110kg Small Smart Bombs, both using global positioning/internal navigation precision guidance. This is equivalent to the design air-to-ground payload for the US Air Force variant of the Joint Strike Fighter, but DARPA is looking for "radically reduced" production and support costs relative to the JSF.
Notionally, DARPA sees the UCAV system being deployed and operational anywhere in the world within 24h. The vehicle would be operated from NATO-standard 2,400m (8,000ft) runways, alongside manned aircraft. The mission control station could be land-, sea- or air-based and allow simultaneous management of more than one vehicle.
To keep costs down, on-board avionics will be minimised and will be designed to be tested, replaced and upgraded even when the vehicle is dormant. DARPA expects the UCAV to be maintained in flight-ready storage for up to a year between operations. On-board avionics will provide autonomous functions such as collision avoidance, self-defence and attack manoeuvring, plus the ability to self-diagnose problems and determine autonomously whether to return to base or terminate the flight.
To provide the mission control station with the situational awareness required to permit lethal operations, but without making the air vehicle too expensive, DARPA says on-board and off-board sensor information will be combined to enable precise location and identification of targets. The aim is to provide the range and accuracy required to cue and release weapons in adverse weather, day or night.
Such a concept requires a robust communications link between the control station and the air vehicle, and DARPA envisages the use of wide-area and local-area, line-of-sight and over-the-horizon, networks. While a wide area network would connect the air vehicle with stand-off sensor platforms as well as the mission control station, a local area network would link the UCAV with accompanying manned strike aircraft. Such networks must be "bullet-proof", DARPA stresses.
The communications bandwidth required will be determined by the degree of real-time control to be exercised over the air vehicle. The concept is for the control station to manage the mission by modifying a preprogrammed plan stored on-board the UCAV, rather than by remotely piloting the aircraft. The degree of autonomy permitted to the vehicle is expected to vary throughout the mission, and lethal operations will require human authorisation, but DARPA expects the UCAV to be capable of autonomously engaging pop-up threats.
Source: Flight International
