Aviation

DARPA has selected The Boeing Company to build its Experimental Spaceplane (XS-1)

DARPA has selected The Boeing Company to complete advanced design work for the Agency’s Experimental Spaceplane (XS-1) program, which aims to build and fly the first of an entirely new class of hypersonic aircraft that would bolster national security by providing short-notice, low-cost access to space. The program aims to achieve a capability well out of reach today—launches to low Earth orbit in days, as compared to the months or years of preparation currently needed to get a single satellite on orbit. Success will depend upon significant advances in both technical capabilities and ground operations, but would revolutionize the Nation’s ability to recover from a catastrophic loss of military or commercial satellites, upon which the Nation today is critically dependent.
“The XS-1 would be neither a traditional airplane nor a conventional launch vehicle but rather a combination of the two, with the goal of lowering launch costs by a factor of ten and replacing today’s frustratingly long wait time with launch on demand,” said Jess Sponable, DARPA program manager. “We’re very pleased with Boeing’s progress on the XS-1 through Phase 1 of the program and look forward to continuing our close collaboration in this newly funded progression to Phases 2 and 3—fabrication and flight.”

The XS-1 program envisions a fully reusable unmanned vehicle, roughly the size of a business jet, which would take off vertically like a rocket and fly to hypersonic speeds. The vehicle would be launched with no external boosters, powered solely by self-contained cryogenic propellants.

Upon reaching a high suborbital altitude, the booster would release an expendable upper stage able to deploy a 3,000-pound satellite to polar orbit. The reusable first stage would then bank and return to Earth, landing horizontally like an aircraft, and be prepared for the next flight, potentially within hours.
In its pursuit of aircraft-like operability, reliability, and cost-efficiency, DARPA and Boeing are planning to conduct a flight test demonstration of XS-1 technology, flying 10 times in 10 days, with an additional final flight carrying the upper-stage payload delivery system. If successful, the program could help enable a commercial service in the future that could operate with recurring costs of as little as $5 million or less per launch, including the cost of an expendable upper stage, assuming a recurring flight rate of at least ten flights per year—a small fraction of the cost of launch systems the U.S. military currently uses for similarly sized payloads. (Note that goal is for actual cost, not commercial price, which would be determined in part by market forces.)
To achieve these goals, XS-1 designers plan to take advantage of technologies and support systems that have enhanced the reliability and fast turnaround of military aircraft. For example, easily accessible subsystem components configured as line replaceable units would be used wherever practical to enable quick maintenance and repairs.

The XS-1 Phase 2/3 design also intends to increase efficiencies by integrating numerous state-of-the-art technologies, including some previously developed by DARPA, NASA, and the U.S. Air Force. For example, the XS-1 technology demonstrator’s propulsion system is an Aerojet Rocketdyne AR-22 engine, a version of the legacy Space Shuttle main engine (SSME).

XS-1 Phase 2 includes design, construction, and testing of the technology demonstration vehicle through 2019. It calls for initially firing the vehicle’s engine on the ground 10 times in 10 days to demonstrate propulsion readiness for flight tests.
Phase 3 objectives include 12 to 15 flight tests, currently scheduled for 2020. After multiple shakedown flights to reduce risk, the XS-1 would aim to fly 10 times over 10 consecutive days, at first without payloads and at speeds as fast as Mach 5. Subsequent flights are planned to fly as fast as Mach 10, and deliver a demonstration payload between 900 pounds and 3,000 pounds into low Earth orbit.
Another goal of the program is to encourage the broader commercial launch sector to adopt useful XS-1 approaches, processes, and technologies that facilitate launch on demand and rapid turnaround—important military and commercial needs for the 21st century. Toward that goal, DARPA intends to release selected data from its Phase 2/3 tests and will provide to all interested commercial entities the relevant specs for potential payloads.
“We’re delighted to see this truly futuristic capability coming closer to reality,” said Brad Tousley, director of DARPA’s Tactical Technology Office (TTO), which oversees XS-1. “Demonstration of aircraft-like, on-demand, and routine access to space is important for meeting critical Defense Department needs and could help open the door to a range of next-generation commercial opportunities.”

Aviation

Exploring the Different Types of Helicopter Rotor Systems and the Science Behind Them

Helicopters are unique aircraft that use rotating blades, called rotors, to generate lift and enable flight. The design of these rotor systems is crucial because it affects how helicopters perform, maneuver, and respond to different flying conditions.

There are several types of helicopter rotor systems, each with its own advantages and specific uses. Understanding these systems helps us appreciate the engineering behind helicopters and their diverse capabilities, from search and rescue missions to military operations and aerial photography.

In this Video, we will explore the main types of helicopter rotor systems and how they contribute to the helicopter’s functionality and performance.

1. Single Rotor System

The single rotor system is characterized by a single main rotor blade that is responsible for generating lift. To counteract the torque produced by this rotor, a tail rotor is used. This setup is essential for maintaining directional control and stability during flight.

Uses: This design is prevalent in most conventional helicopters, including iconic models such as the Bell 206 and the Robinson R22. The simplicity of the single rotor system not only reduces mechanical complexity but also enhances efficiency. As a result, it is favored for a variety of applications, including aerial tours, law enforcement, and emergency medical services, where reliability and straightforward operation are paramount.

2. Tandem Rotor System

The tandem rotor system features two parallel rotors of equal size that rotate in opposite directions. This counter-rotation helps to cancel out the torque that each rotor would otherwise produce, resulting in a balanced and stable flight profile.

Uses: This configuration is typically employed in heavy-lift helicopters, such as the CH-47 Chinook. The tandem design allows for an increased payload capacity and enhanced stability, making it particularly effective for transporting troops, equipment, and supplies in military operations, as well as for civilian applications like logging and construction, where heavy lifting is required.

3. Coaxial Rotor System

The coaxial rotor system consists of two rotors mounted one above the other on the same mast, rotating in opposite directions. This innovative design minimizes the need for a tail rotor, allowing for a more compact helicopter structure.

Uses: Coaxial rotor systems can be found in helicopters such as the Kamov Ka-50. This design offers several advantages, including enhanced lift capabilities, improved maneuverability, and better control in various flight conditions. These features make it particularly suitable for military applications, where agility and quick response times are crucial, as well as for specific civilian operations that require high performance in tight spaces.

4. Intermeshing Rotor System

The intermeshing rotor system consists of two rotors that rotate in opposite directions while intersecting each other, but without colliding. This unique configuration creates a highly efficient aerodynamic profile.

Uses: This system is utilized in helicopters like the Kaman K-MAX, designed specifically for heavy lifting and aerial work. The intermeshing rotors provide remarkable stability and lift capabilities, making it particularly effective for operations in confined spaces, such as urban environments or dense forests. It is ideal for missions that involve heavy external loads, including construction, firefighting, and disaster relief efforts.

5. Transverse rotor system

The transverse rotor system has two parallel rotors that spin in opposite directions, improving lift and stability. This design enhances the aircraft’s aerodynamic efficiency and maneuverability.

A notable example of this system is the V-22 Osprey, a tiltrotor aircraft that merges helicopter vertical lift with the speed of a fixed-wing plane. allowing the Osprey to operate in tough environments like urban areas and remote locations. It can carry heavy loads and personnel, making it suitable for troop transport, search and rescue, medical evacuation, and logistical support in military operations. Overall, the transverse rotor system enhances the V-22 Osprey’s effectiveness and operational flexibility.

6. Compound Rotor System

The compound rotor system combines traditional rotor systems with fixed wings and other aerodynamic features to enhance efficiency and speed. This hybrid approach allows for greater aerodynamic performance than standard rotorcraft.

Uses: Advanced helicopters like the Sikorsky X2 and Boeing’s DBF (Defiant) utilize the compound rotor system. These helicopters are designed for higher speeds and longer ranges, making them suitable for military operations, search-and-rescue missions, and law enforcement tasks where rapid response and extended operational capabilities are essential.

7. NOTAR system

NOTAR system replaces the traditional tail rotor with a ducted fan and directional airflow to counter the torque from the main rotor. It works by pushing air through the tail boom and out through side vents, creating thrust that stabilizes the helicopter. This design reduces noise, boosts safety, and cuts down on maintenance.

Uses: The NOTAR system is found in helicopters like the MD 520N and MD 902 Explorer. Without an exposed tail rotor, it lowers the risk of rotor strikes, making it safer for operations in tight spaces. Its quieter performance is ideal for missions where low noise is needed, such as urban air operations, police work, and medical evacuations.