A comprehensive resource on the past, present, and future of space technology

Researchers in optics, materials processing, and telecommunications require a reference that can provide a quick study of a number of basic topics in space science. The two-volume Encyclopedia of Space Science and Technology represents an ambitious collection of the underlying physical principles of rockets, satellites, and space stations; what is known by astronomers about the sun, planets, galaxy, and universe; and the effect of the space environment on human and other biological systems. The Encyclopedia covers a variety of fundamental topics, including:
* A state-of-the-art summary of the engineering involved in launching a rocket or satellite
* The control systems involved on the ground, in orbit, or in deep space
* Manufacturing in space from planetary and other resources

Physicists, astronomers, engineers, and materials and computer scientists, as well as professionals in the aircraft, telecommunication, satellite, optical, and computer industries and the government agencies, will find the Encyclopedia to be an indispensable resource.

HANS MARK, PhD, is presently associated with the Aerospace Engineering & Mechanics Division of Woolrich Labs at the University of Texas at Austin. He has previously served as the deputy director of NASA and as chancellor of the University of Texas System.

Encyclopedia of Space Science and Technology, 2 Volume Set

John Wiley & Sons

Copyright © 2003 Hans Mark
All right reserved.
ISBN: 978-0-471-32408-9

Chapter One

A

AIR AND SHIP-BASED SPACE LAUNCH VEHICLES

Introduction

In 1957, the Soviet Union placed the first man-made object in orbit around the earth. Since then, numerous launch vehicles have been developed to improve the performance, reliability, and cost of placing objects in orbit. By one estimate, roughly 75 active space launch vehicles either have established flight records or are planning an inaugural launch within the year. This does not include the numerous launch vehicles from around the world that are no longer operational such as the Jupiter, Redstone, Juno, Saturn, Scout, Thor, Vanguard, and Conestoga family of rockets from the United States or the N-1 from the former Soviet Union, to name just a few. Despite the many differences among all of these launch vehicles from both past and present, one common element can be found in all but four of them: they are ground-launched. Of the four exceptions, two are air-launched (NOTSNIK and Pegasus), one is ship-launched (Sea Launch), and one is submarine-launched (Shtil). It is important to keep in mind that numerous air-launched and ship-launched suborbital launch systems are in use by militaries, commercial entities, and educational institutions. However, the four mentioned are the only mobile launch systems that can place objects into a sustainable Earth orbit.

Mobile Space-Launched Vehicles

Project Pilot (NOTSNIK). NOTSNIK is the oldest and, until recently, the least well known of the four mobile space-launched systems. Following the launch of Sputnik by the Soviet Union, President Eisenhower’s administration elicited proposals to launch a satellite into orbit. The Naval Ordinance Test Station (NOTS) located at China Lake in California proposed launching a rocket from a jet fighter. The idea is the same as that of the current Pegasus vehicle: reduce the amount of energy needed to place a payload into orbit by launching it above the denser portion of the atmosphere. In this fashion, the engineers at NOTS designed a vehicle from existing rocket motors that could place a 2-pound satellite in a 1500-mile-high orbit. The engineers recognized the energy savings from such a launch concept and also the utility of such a flexible platform. Launching from a jet fighter could, theoretically, place a satellite into any orbit from anywhere in the world at any time.

The U.S. Navy accepted the proposal from NOTS in 1958, by some accounts as a safety net in the event that the ongoing Vanguard project was unsuccessful. The program was officially called Project Pilot, but the engineers at NOTS preferred the name NOTSNIK in direct reference to the Soviet satellite that was currently orbiting above them and the rest of the world. A Douglas Aircraft F4D-1 Skyray was the carrier aircraft for the rocket and consequently was considered the first stage. The second and third stages were modified antisubmarine missiles. The final stage was taken from a Vanguard rocket. The entire launch vehicle measured a mere 14 feet in length and had four fins at the aft end that provided a span of 5 feet.

The NOTSNIK was launched six times from an altitude of about 41,000 ft. Four of those launches ended in known failures. However, the results of two have never been verified. Some in the program insist that they achieved their goal of placing the small payload of diagnostic instruments in orbit. At least one ground station in New Zealand picked up a signal in the right place at the right time. However, confirmation that the signal was from the NOTSNIK payload was never established. Even the possibility of a success was veiled in secrecy for more than 40 years for, by all accounts, two critical reasons. The first was that in the days following the early embarrassments of Vanguard, the Eisenhower administration did not want to claim success unless it was absolutely certain. The second reason was that a mobile air-launched system that could reach orbit had extremely appealing military applications. However, the tactical advantages of such a system were far outweighed by the strategic consequences, as stated in the Antiballistic Missile (ABM) Treaty between the United States and the former Soviet Union that was concluded in 1972:

Further, to decrease the pressures of technological change and its unsettling impact on the strategic balance, both sides agree to prohibit development, testing, or deployment of sea-based, air-based, or space-based ABM systems and their components, along with mobile land-based ABM systems. Should future technology bring forth new ABM systems ‘based on other physical principles’ than those employed in current systems, it was agreed that limiting such systems would be discussed, in accordance with the Treaty’s provisions for consultation and amendment.

Pegasus. Roughly 30 years later, while NOTSNIK remained an official government secret, the idea of launching payloads into space from an airborne platform was revisited in the form of the Pegasus launch vehicle. The driving forces behind NOTSNIK and Pegasus were essentially the same. An air-launched space vehicle provides several advantages compared with ground-based counterparts.

As an example, Pegasus is launched at an altitude of 39,000 ft, which is above a significant portion of the atmosphere. As mentioned, with NOTSNIK, this eliminates the need for extra performance that would otherwise be needed to overcome atmospheric forces. This also implies that the structural components of the vehicle can be lighter, which improves the efficiency of the rocket as a whole. The energy required from the launch vehicle is also reduced by the speed already achieved by the carrier aircraft. An air-launched system also allows applying more of the impulse of the first stage along the velocity vector. This is a more efficient use of the vehicle’s energy than that of ground-launched vehicles that must first apply the thrust almost perpendicular to the velocity vector already imparted by Earth’s rotation. These factors combine to produce a requirement for a velocity increment that is on the order of 10% less than a comparable ground-launched rocket.

The Pegasus vehicle is a winged, three-stage, solid rocket booster (Fig. 1). It is the first space-launched vehicle developed solely with commercial funding. Three versions have been developed and flown over the years: Standard, Hybrid, and XL. The XL is the only vehicle within the Pegasus family currently in production. The XL is roughly 10,000 lbm heavier than the Standard or Hybrid models and is roughly 6 ft longer. Because the XL extends farther aft beneath the L-1011 carrier aircraft, the port and starboard fins become an obstacle to the landing gear doors. To correct this problem, the port and starboard fins were modified to include an anhedral of 23. To maintain commonality between the various members of the Pegasus family of vehicles, the same anhedral was introduced into the Standard vehicle, which was then given the designation Pegasus Hybrid. Other than the anhedral of the fins, the Standard and Hybrid vehicles are exactly the same. The Standard, the first Pegasus vehicle built, was flown on six missions. The Hybrid vehicle has flown four times. The XL vehicle has flown 21 times. Of 31 Pegasus launches, only three missions failed to reach orbit.

The Pegasus XL was designed and developed to provide increased performance above and beyond that provided by the Standard and Hybrid vehicles. A typical Pegasus XL vehicle weighs roughly 51,000 lbm at launch, is 55.4 ft long and 50 inches in diameter, and the wingspan is 22 ft. At launch, the Pegasus XL is carried aloft by the company’s carrier aircraft, a modified L-1011, which originally saw commercial service with Air Canada. The vehicle is dropped from an altitude of 39,000 ft at Mach 0.8. Five seconds after release from the L-1011, the first stage ignites and the vehicle’s on-board flight computer continues the sequence of events that eventually lead to orbital insertion. The brief coast period between drop and stage one ignition is designed to provide a safe distance between the L-1011 and the launch vehicle.

The Pegasus Standard vehicle was originally dropped from a NASA-owned and operated B-52. The Pegasus vehicle was attached to one of the pylons underneath the starboard wing much in the same manner as the early supersonic and hypersonic test vehicles such as the X-15. For a variety of reasons, Orbital purchased and modified the L-1011 to facilitate all future launches.

Unlike the B-52 that supported initial Pegasus launches, the L-1011 carries the Pegasus vehicle underneath the fuselage rather than underneath the wing. Once Pegasus is ready to be mated to the carrier aircraft, it is towed from Orbital’s integration facility at VAFB to the plane on the Assembly and Integration Trailer (AIT). Regardless of where the launch is to take place, the Pegasus is always integrated and mated to the L-1011 at VAFB. From there, the launch system can travel to any location in the world for launch. There is enough ground clearance for the L-1011 to take off and land with Pegasus attached underneath. However, the added height of the AIT underneath Pegasus requires raising the L-1011 off the ground slightly by hydraulic jacks to mate Pegasus to the carrier aircraft (Fig. 2). While mated to the L-1011, the vertical rudder actually protrudes into the plane’s fuselage in a compartment specifically designed for this purpose. When mating the Pegasus to the L-1011, the rudder is usually detached from the Pegasus vehicle and placed inside the housing first. Then the Pegasus is rolled underneath the L-1011 and attached to the rudder and then to the plane. Removing the rudder first minimizes the height to which the L-1011 needs to be raised for the mating process. The entire mating process from rollout to mating takes about 6 hours. Pegasus is attached to the L-1011 using four hooks on the center box of the wing and a fifth hook on the forward portion of the vehicle. The inside of the airplane has been stripped of all unnecessary equipment and hardware. Up front in what would normally be the first class cabin are eight seats for personnel during ferry flights from VAFB to the launch site of interest and two computer stations from which personnel can monitor the health of the vehicle and the payload. The rest of the interior of the cabin has been completely gutted. Access to the rear portion of the aircraft cabin is obtained through a galley door.

Unlike most other launch vehicles in the U.S. fleet, the Pegasus launch vehicle is integrated horizontally on the AIT (Fig. 3). Horizontal integration facilitates easy access to the vehicle and eliminates the need for high bays and large cranes. Components are received as needed either from groups within Orbital Sciences or from outside vendors. To ensure that all of the major flight hardware and software is thoroughly tested before flight, Pegasus, like many other vehicles, is subjected to a series of “fly to orbit” simulations at various stages of the integration process. Four flight tests are normally performed. The first tests the three stages individually. The second test is conducted after the three stages are electrically mated together. The third test is performed after the three stages are electrically and mechanically mated and the stack is electrically mated to the payload. The fourth and final flight test is performed once the payload has been mechanically mated to the rest of the vehicle and the half of the fairing that includes the pyro devices necessary for jettisoning the shroud is electrically mated. These tests are intended to verify that various systems function and also respond as expected to known disturbances. If the inertial measurement unit (IMU) onboard receives data to indicate that an unexpected attitude change has occurred, will the fins or thrust vector control systems respond accordingly? Are all the commands to the various subsystems appropriate, and do those subsystems respond appropriately? Once the Pegasus vehicle has been mated to the L-1011 carrier aircraft, one last test is performed, called the Combined Systems Test (CST). This test verifies that the launch vehicle and the carrier aircraft are communicating as expected. This is particularly important since the vehicle’s health can be monitored both from telemetry that is broadcast from the vehicle to the ground via antennas on Pegasus and also by the computer stations inside the L-1011 via hardwired electrical connections. More importantly, some data and commands are sent to the Pegasus vehicle before launch. The only method currently available for accomplishing this transfer of data is through the electrical connections between the Pegasus vehicle and the carrier aircraft.

To be fully mobile, the Pegasus launch system must also be fully self-contained. Except for those services provided by the range (such as radar coverage), the L-1011 can transport all of the equipment required to support a launch of Pegasus, including, of course, Pegasus itself (Fig. 4). Some launches take place off the coast of California where the Western Range (based at VAFB) is the lead range. In these instances, no ferry flight is required. The L-1011 simply takes off from VAFB and flies to the designated drop point roughly 100 nmi out to sea. The checklist that is processed in the control room on the day of launch requires about 4 to 5 hours to complete. The L-1011 usually takes off an hour before the scheduled launch time. If all systems are “go,” as determined by the mission team members in the control room, the launch conductor on the ground commands the pilot of the L-1011 to drop the Pegasus from the carrier aircraft.

Shtil. In a classic example of turning swords into plowshares, the Russian Navy developed a satellite delivery system for nonmilitary applications that uses a submarine-launched. The SS-N-23 (NATO’s designation) is a three-stage liquid-fueled vehicle that can deliver small satellites to low Earth orbit. Very little is known about this launch vehicle service including performance to various altitudes and inclinations. What is known is that two satellites belonging to the Technical University of Berlin were successfully launched in 1998 from a Russian submarine for the stunningly low price of $150,000. Some sources indicate that the typical commercial price for a Shtil launch is actually in the neighborhood of $500,000. There are two possible reasons for the low cost of a Shtil launch. The first is that more than 200 missiles have already been produced by the Russian military. There is also speculation that offering commercial launch services provides a way to maintain proficiency in launching missiles without using precious military funding. One disadvantage of this system is that the Shitl vehicle likely does not have enough performance to achieve circular orbits in the medium to high Low Earth Orbit (LEO) altitudes. This is a direct result of the Shtil’s heritage as a ballistic missile first and foremost.

Sea Launch. The most recent mobile launch system is the Sea Launch vehicle which is launched from a converted oil-drilling platform along the equator (Fig. 5). Sea Launch is both the name of the launch vehicle and the name of the international joint venture that provides the launch services. The partnership is comprised of Boeing, KB Yuzhnoye of Ukraine, which provides the two Zenit stages, and RSC Energia of Russia, which provides the Block DM-SL upper stage. The launch vehicle and payload integration takes place at the vehicle’s home port of Long Beach, California. Once integration is complete, the launch vehicle is loaded onto the converted oil-drilling platform and towed to a predetermined launch location at the equator, specifically 1541 West. Once on site, the Zenit 3SL is raised into its launch attitude (vertical) and launched. A second ship that houses mission personnel and the control room monitors the launch from nearby. The vehicle itself is a little less than 200 ft long and roughly 13 ft in diameter. The performance to Geosynchronous Transfer Orbit (GTO) is approximately 5250 kg. “In terms of spacecraft mass in final orbit, this would be equivalent to approximately 6000 kg of payload capability if launched from Cape Canaveral, because the spacecraft does not need to perform a plane change maneuver during the Geosynchronous Earth Orbit (GEO) circularization burn”.

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