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22-08-2007, 18:40
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מומחה לתעופה, תעופה צבאית, חלל ולווינות. חוקר בכיר במכון פישר
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חבר מתאריך: 02.07.05
הודעות: 11,691
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כטב"מ המשוגר באמצעות טיל בליסטי
בתגובה להודעה מספר 1 שנכתבה על ידי טל ענבר שמתחילה ב "הכטב"ם לאן? סוגיות בפיתוח והפעלת כלי טייס בלתי מאויישים"
זו התוכנית הנבחנת בימים אלה על ידי DARPA. (והסיבה להקפצת אשכול זה - שפוטנציאל הדיון על תכניו טרם מוצה).
ידיעה מעניינת ביותר מתוך Defense News
The U.S. Defense Advanced Research Projects Agency (DARPA) has launched an exploratory development program with the goal of placing a high-altitude, long-endurance UAV anywhere on the planet within one hour. Delivered by intercontinental ballistic missile (ICBM), the UAV will be required to remain on station until it is relieved or its mission finished.
DARPA’s Rapid Eye initiative could ultimately emerge as the intelligence, surveillance and reconnaissance (ISR) portion of a larger U.S. requirement for a Prompt Global Strike force able to function independently of overseas bases or nearby naval forces. The Air Force has proposed a stealthy, subsonic manned bomber that would enter service after 2018, but it and the Navy are also considering equipping land- and sea-based ICBMs with conventional warheads.
The Navy’s program is based on the Trident submarine-launched ballistic missile, while the Air Force is developing the Common Aero Vehicle (CAV) — a hypersonic glider that could carry conventional munitions atop modified Minuteman or Peacekeeper missiles. The CAV has also been proposed as a UAV carrier.
A parallel effort, Conventional Strike Missile, omits the glider and swaps the ICBMs’ nuclear warheads for sensor-fused submunitions or other precision-guided weapons.
But some fear that blurring the distinction between conventional and nuclear weapons is inherently dangerous, because the launch of an ICBM carrying a conventional warhead or a UAV might be mistaken for a nuclear attack.
“The Chinese only have a minimal nuclear deterrent and Russia’s is deteriorating rapidly, so both may be under pressure to launch a retaliatory strike before they know what we’re really up to,” said Loren Thompson, chief operating officer of the Lexington Group, Arlington, Va.
To reduce that risk, the Air Force plans to base the conventional missiles along the U.S. coasts in California and Florida, far from its Cold War-era missile silos.
It would be more difficult for the Navy to segregate its conventional Tridents from nuclear-armed versions on the same submarines. Inspections could alleviate concerns, but the risk would rise dramatically if the United States elected to fire its conventionally armed ICBMs quickly during a crisis.
In tactical terms, a short-notice launch also implies a requirement for instant reconnaissance of the target area immediately before the attack and a detailed poststrike damage assessment.
“Operationally, that’s a big plus,” Thompson said. “Packing a UAV into the top of a ballistic missile would provide you with a combination of promptness for time-sensitive targets, with precision in terms of the desired effects. This would cover you for a range of possibilities. We might see terrorists preparing to deliver a nuclear weapon on a mobile launcher and be under extreme time pressure to destroy it ... We’re talking about a category of targets where the consequences of delaying are so severe that we can’t do the job by the normal means.”
Using existing technologies, DARPA seeks to develop a system able to fire an ICBM into space, and upon re-entry into the Earth’s atmosphere, slow its payload compartment enough to deploy a midsized UAV. The UAV’s engine, sensors and communications gear would then be activated and the vehicle maintained on station for seven to 15 hours.
The requirements stipulate the use of an existing launch vehicle, or one that will be in the U.S. inventory by 2009. The UAV must be able to carry a 500-pound payload and meet a 5-kilowatt power requirement, and may require folding or inflatable wings to fit inside the rocket. Lighter-than-air vehicles or approaches that employ buoyant flight will not be considered.
Riding the Minotaur
For now, launch services provider Orbital Sciences appears closest to offering compatible solid-fuel boosters. Its Minotaur I rocket, which made its first flight in January 2000 and placed TacSat-2 in orbit late last year, combines Minuteman II first and second stages with two additional stages borrowed from the company’s Pegasus and Taurus commercial launch vehicles. Minotaur I has a mass-to-orbit of up to 580 kilograms.
The much larger Minotaur IV, which derives its power from decommissioned Peacekeeper missile stages, can boost more than 1,750 kilograms. Now under construction, the first Minotaur IV is slated to boost the Air Force’s first Space-Based Infrared System surveillance satellite into orbit late next year.
“Minotaur has really gained a lot of interest in the past year and a half, as more operationally responsive space missions are considered,” said Barry Beneski, an Orbital Sciences spokesman. “In terms of Rapid Eye, high-speed separation of the payload seems like the greatest challenge. ... We did a Mach 9 separation for the NASA X-43A Hyper-X program, so this is not a great hurdle for us.”
Rapid Eye would arrive on station faster than U.S.-based ISR platforms, and would be able to loiter over the target long enough for these assets to respond. As DARPA sees it, the missile-launched UAV would have sufficient range to be recovered at a friendly air base and be invulnerable to all but the most sophisticated countermeasures.
Equipped with a synthetic aperture radar, a ground moving target indicator, and high-bandwidth communications and electro-optical sensors, the UAV would provide satellite-quality ISR with regional coverage.
To make this happen, however, a number of technical challenges must be overcome: packaging a high-aspect-ratio aircraft (one with long, thin wings) into a missile shroud; crafting a re-entry decelerator with low stowed volume but enough mass to slow the re-entry vehicle high in the atmosphere; deploying a large, folded aircraft; and designing a UAV propulsion system efficient in low oxygen levels and at low speeds.
Recent developments are encouraging, however, and researchers at NASA’s Langley research center might already have the solution in an expendable UAV proposed to explore Mars. Developed between 2001 and 2006, the Aerial Regional-scale Environmental Survey of Mars vehicle is folded to fit within an entry aeroshell and performs a midair extraction and unfolding after a 10-month spaceflight.
Some other promising designs:
• NASA’s Ames research center’s Mars airplane prototype, balloon-launched from 103,000 feet, also explored the ability to fold body and wings for spacecraft deployment.
• Big Blue (Baseline Inflatable-wing Glider Balloon-Launched Unmanned Experiment), from a University of Kentucky/Oklahoma State University team, is the result of an effort to study the feasibility of inflatable wings in the Martian environment. Big Blue is the first UAV to demonstrate a rigid, inflatable wing at high altitudes.
• The U.S. Naval Research Laboratory has built a number of technology demonstration UAVs in recent years, some with attributes that could one day appear on the Rapid Eye aircraft.
DARPA anticipates a four-phase plan for Rapid Eye, with the first phase allowing multiple contract awards for system design and risk reduction. Phase II will narrow the field to one or two designs for subscale testing, with Phase III incorporating detailed design work. The last phase would require construction and flight-testing of a complete system.
Initial proposals are due by Oct. 14; contract awards are expected by year’s end. • |
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