Technical Description Development of Payload Fairings for Launch Vehicle It is expected that launches of satellites will continue to increase in the future across the world including emerging and developing countries due to the benefits of images and positional information acquired by satellites. The fairing is a component that protects satellites on the top of the launch vehicle. This component plays an important role in the satellite launch business because the temperature and acoustic vibration environment around the satellite is critical along with the launch cost and the orbit injection accuracy. Kawasaki has successfully produced a large fairing ©JAXA for the H-II Launch Vehicle for the first time in Japan. Since then, we have made technical improvements on an ongoing basis to continue supplying high- performance fairings at a low cost. plan to put them on the market in about 2020. Introduction Since developing the payload fairing for the H-II Launch National security, disaster prevention and private Vehicle in 1984, Kawasaki has continued to improve its services that use images and positional information technology through the H-IIA/H-IIB Launch Vehicles and acquired by satellites have become common, and the the Epsilon Launch Vehicle1), and now supplies payload space industry market is expanding. On the other hand, fairings for all of Japan's major launch vehicles. At present, the entry of American entrepreneurs into the satellite Kawasaki is in charge of developing the payload fairing for launch business is exerting downward pressure on prices. the H3 Launch Vehicle, and is engaged in developing of This is leading to the need to supply high-performance high-performance payload fairings at low cost with the aim launch vehicles at lower prices. of launching the first vehicle in fiscal 2020. 1 Background 2 Payload fairing There are two types of satellites. One is government As Fig. 1 shows, a payload fairing keeps the internal satellites as represented by reconnaissance and weather temperature/humidity and cleanliness (in the space where satellites; the other is commercial satellites as a satellite is mounted) constant until the launch vehicle represented by communications and broadcasting lifts off, and reduces aerodynamic drag during the flight. satellites. In the satellite launch business, aerospace At the same time it helps to protect the satellite from companies from Japan, the US, Europe and Russia have aerodynamic heating and acoustic vibration. Once the continued to compete against one other for 20 to 30 launch vehicle reaches an altitude of about 100 km, where commercial satellites a year. In 2010, however, as Space the atmosphere is sufficiently rarefied, the payload fairing Exploration Technologies Corp. (SpaceX) made inroads into splits into two pieces by actuating its separation system, this business with its low-priced Falcon 9 launch vehicle, rotates on a hinge and separates from the launch vehicle. prices plunged. Moreover, the progress of launch vehicle Figure 2 shows the structure of payload fairing. It has technology from emerging countries such as China and two half-shell bodies that are joined together by the India is remarkable, and competition is expected to further separation system (vertical separation system) in the axial intensify in the future. Consequently, Japan, the US and direction, and they are joined to the body of the launch Europe are now promoting development of next- vehicle by the separation system (horizontal separation generation, cost-competitive large launch vehicles, and system) in the circumference direction. The payload fairing 29 p29-34_技術04E_180906.indd 29 2018/09/17 12:00:05 1/2 stage separation Satellite separation Payload fairing separation (altitude about 100 km) during ight In ight Landing in the sea Before lift-off to lift-off Fig. 1 Launch sequence Insulator Vertical separation system (payload fairing split into two pieces) Acoustic blanket (internal) Access door for satellite work Horizontal separation system Payload fairing opening hinge tting (separation from the body of launch vehicle) Fig. 2 Configuration of payload fairing has an access door used by satellite crew for maintenance 3 Technology to support payload and a radio transparent window for communication fairings between satellites and their launch facilities. Moreover, the payload fairing has an air-conditioning door draw in (1) Separation systems clean air into the inside at the launch facility, insulators to Separation systems are the most technically difficult prevent the body structure and interior from heating up components of payload fairings to design and make. As due to aerodynamic heating, and an acoustic blanket as separation systems are strength members that connect sound-absorbing material to reduce acoustic vibration structures, they must be strong enough to endure the caused by engines and the atmosphere. aerodynamic loads generated at supersonic speeds. Yet To minimize the weight of the satellite, which has the strength needs to be low enough to separate payload many delicate electronic components aboard, it is fairings with minimal energy to reduce the shock to important to ease the environmental conditions around satellites during separation. This means payload fairings the satellite such as heat, acoustic vibration and shock. must be designed to bring such mutually contradictory This is the role payload fairings play. requirements into balance. As faulty payload fairing Kawasaki Technical Review No.179 30 October 2018 p29-34_技術04E_180906.indd 30 2018/09/17 12:00:06 Technical Description separation directly leads to mission failure, high reliability (2) Environmental mitigation is critical. ( i ) Insulators Kawasaki has decided to develop Japan's unique To prevent rises in temperature of body structures due separation system based on the frangible bolt (notched bolt) to the heat caused by the friction against the atmosphere, method. This method was used in a canopy emergency and maintain appropriate temperatures around satellites, separation system for fighter aircraft at the time when insulators are applied to the outer surfaces of payload development of the payload fairing for the H-II Launch fairings. Kawasaki developed a light-weight insulator for Vehicle was underway. Priority was given to higher reliability the payload fairing of the H-II Launch Vehicle by mixing and lower cost. This method employs explosive force to cut glass microballoons into silicone resin, and achieved both a bolt that features a V-shaped groove (notch) for easier weight reduction and heat insulation improvement at the cutting. Although development took a long time, as even same time. slight changes in parameters of materials, notch shapes (ii) Acoustic blanket and plate thickness of stainless steel oval tube cause bolt To reduce acoustic vibration caused by engines and uncut or oval tube ruptures that lead to faulty separation and friction against the atmosphere, acoustic blankets are satellite contamination, the great number of tests have applied to the inner surfaces of payload fairings. Glass resulted in highly reliable separation systems that are can wool and resin foam are used for this insulator, and the be applied new types of fairings even today (Fig. 3). insulating material is packed in filter-equipped covers to Notch bolt (frangible bolt) Housing Explosive Holder Stainless steel oval tube (oval shaped before separation) (b) Before separation Notch (V-shaped groove) Stainless steel oval tube (a) Notch bolt (returned to round-shape by combustion of explosive) Notch bolt is cut (c) After separation Fig. 3 Separation mechanism of payload fairing from Kawasaki 31 p29-34_技術04E_180906.indd 31 2018/09/17 12:00:11 prevent dust from escaping into the satellite and payload fairings (4/4D-LS, 5/4D) capable of carrying compartment. The aim is to prevent the covers from two satellites at the same time were developed. rupturing in decompressed environment as the launch To cope with the increased variations of fairings, many vehicle climbs. This means decompression, in addition to different molds are needed to shape the payload fairings, weight minimization, is also an important factor in and many assembly jigs and tools are required. However, designing launch-vehicle equipment. to reduce non-recurring costs as much as possible, we have achieved commonality of panels among respective (3) Structure and shape types of payload fairings, and jigs and tools include length- ( i ) Structure adjusting functions and other ideas. Conventional payload fairings have a lightweight and highly bending stiffness honeycomb sandwich structure 4 Approaches to new technology that can reduce deformation at the time of opening as much as possible and reduce aerodynamic drag, ensuring (1) Approaches to the Epsilon Launch Vehicle more space to carry satellites within a smaller diameter. The development of payload fairings for the Epsilon The sandwich structure joins thin plates to both sides Launch Vehicle started in 2010. For this project, Kawasaki of a lightweight core material. The advantage of this addressed new technology development by following the structure is that increasing the core thickness makes it designs of the H-II series such as H-IIA/H-IIB with the aim very difficult for the sandwich structure to deform while of reducing costs and improving convenience. minimizing any weight increase. A structure that uses a ( i ) Half-shell integrally submerging body structure honeycomb core for its core material is called a Payload