Delta 180 Vector Sum Experiment

A series of SDIO experiments conducted on 5 September 1986 known as the Delta 180 test confirmed the ability of space-based infrared sensors and KEW to perform simulated boostphase intercepts. During this experiment, SDIO completed what was the first equivalent of a boost phase intercept of a target. The Delta 180 mission objectives included observations of a spacecraft against a variety of ranges, tracking a launch vehicle within its plume, and the interception of an accelerating target by an active radar seeker. Additionally, this experiment involved a number of sophisticated sensor experiments, including the collection of data from space on a booster vehicle launched from the White Sands Missile Test Range in New Mexico.

DELTA 180 involved the placement of a DELTA second stage and a Payload Adapter System (PAS) in two 120-nautical-mile-high time-synchronous orbits with slightly different inclinations. This mission, which was fully compliant with the requirements of the 1972 Anti-Ballistic Missile (ABM) Treaty, utilized the restartable upper stage of the Delta 3920 launch vehicle as a target. A direct hit at a closing velocity of 2.9 km/s was achieved from a standoff range of 220 km by an interceptor consisting of a Hughes Phoenix AIM-54C+ air-to-air radar seeker and a specially designed propulsion and control module derived from the Delta 3914 upper Stage. Onboard the second stage target vehicle was an instrumentation suite which provided both pre-encounter and endgame data in the infrared, visible, and ultraviolet portions of the spectrum. as well as guidance data from the engineering flight test of a 1.06 mm laser radar.

Air Force Lieut. General James Abrahamson, SDI's director, argued that the $150 million demonstration proved it is feasible for a smart rock to locate a missile shrouded in its own exhaust plume and track other objects in space. The demonstration, however, was somewhat rigged: the rocket orbits were preprogrammed, and a reflector on the target rocket magnified its image 1,000 times.

The Delta 180 program was spawned by a rare combination of circumstances; a national strategic need; the new, forward looking SDIO; available funding; adaptable hardware; and most importantly, an innovative group of people in government, industry, and academia who became the Delta 180 team. In 1984, the newly established SDIO began working with Johns Hopkins University Applied Physics Laboratory (APL). Their teamwork, with many other subcontractors, began with the successful Delta 180 experiment in 1986, the first in a series of Delta programs that set new standards for accomplishing orbital missions executed rapidly and cost-effectively.

An essential element in strategic defense planning and feasibility assessment is the so-called boost phase intercept, Le., the destruction of enemy ICBMs during the vulnerable powered flight phase, prior to the release of reentry vehicles and decoys. An efficient boost phase defense is essential in order to reduce to manageable proportions the problems of midcourse and terminal defense: it is also extremely challenging due to the limited engagement time available and the requirement for guided intercept of an accelerating target.

With these factors in mind, an early assessment of the feasibility of powered space intercept was deemed to be of the highest importance by the Strategic Defense Initiative Organization. To explore these issues, a program (code named Vector Sum) having as a major goal the space intercept of a thrusting target during powered flight was initiated in May 1985, following completion of a study phase begun in February. This program culminated less than 16 months later in the launch on 5 September 1986 of the NASA McDonnell-Dougias Delta 180 vehicle in the first mission conceived and carried out by SDIO.

The Delta 180 mission provides a good example of focusing on the true objective and meeting it through "out-of-the-box thinking." Soon after President Reagan challenged the military to develop a missile defense, the newly established Strategic Defense Initiative Organization (SDIO) wanted a quick and convincing demonstration of space intercept of a thrusting target. Various aerospace organizations proposed mission concepts, but they were all too long (3-5 years) and too expensive ($300-500M). One reason for the high costs was that all of these concepts envisioned separate launch vehicles for the target and the interceptor.

APL system engineer Michael Griffin and program manager John Dassoulas considered the essence of the problem and came up with the novel idea of carrying both target and interceptor on a single, low-cost Delta launch. Furthermore, both spacecraft could be assembled from subsystems scrounged from various existing missile and launcher systems.

The Vector Sum program originated in January 1985 with a series of informal discussions between staff members of the Johns Hopkins University Applied Physics Laboratory (APL) and the SDIO Kinetic Energy Weapons office concerning possible means of performing a near term experiment in boost-phase intercept. The desired experiment was to be compliant with the 1972 ABM treaty, was to be performed within approximately a year, and was to accomplish safely a space intercept of a target vehicle in powered flight.

Unambiguous statement of these requirements and the fact that they remained unchanged throughout the program contributed in large measure to the ultimate success of the mission. The mission requirements stated above forced several early concept design decisions. To meet the desired schedule, technical approaches requiring substantial development were ruled out. The schedule for the proposed flight experiment seemed difficult but possible for a design restricted to the use of existing hardware components and subsystems, with due allowance for necessary modifications. Use of an approach requiring development of unproven techniques seemed an unacceptable schedule risk.

Streamlined program management and reporting procedures resulted in significant schedule and cost compression; instead of the normal timeline of three to five years at a $300 to $500 million cost, the experiment took fourteen months and cost $150 million. For example, the program adopted an unwritten "badgeless" mentality that effectively removed all organizational impediments to accomplishing the mission. Also, top management exercised prudent, but non-intrusive oversight.

The Delta 180 experiment's primary focus centered on understanding the problems of tracking, guidance, and control for a space intercept of an accelerating target, and demonstrating this in a flight test. What became equally important was the urgent need for multi-spectral data on rocket plumes, post-boost vehicles, and the background against which they would be viewed. At that time, very little sensor data had been collected on intercontinental ballistic missile (ICBM) threats, and no thrusted intercept against a thrusting target had ever been attempted in space.

The Applied Physics Laboratory undertook the role of technical advisor for the overall experiment, and also had the responsibility for designing the sensing spacecraft that was part of the target vehicle. The theme throughout was to understand and develop sensors that SDIO could use in a deployed architecture from ascent through the midcourse phase of a booster trajectory. The team's efforts in supporting SDIO constituted a major element in the assessment of sensor technology. In particular, the development of ultra-violet sensor technology through space-borne observations of rocket plumes provided significant data for use in the development of deployed sensor architecture. The Delta 180 team served as the core that led this effort, provided key technical guidance, and ultimately enabled its success. Their efforts and the resulting success of the experiment proved some of the basic concepts of boost phase intercept.

One early decision was to restrict the experiment to the use of expendable launch vehicies. Payload integration lead times and support requirements argued strongly against a shuttle based test, even assuming that the necessary manifesting priority could be obtained. Accordingly, the recommendation was made to and accepted by SDIO to restrict the mission to expendables. This decision proved sadly appropriate a year later in the wake of the Challenger 51-L disaster.

The decision to launch on an expendable vehicle became, within days, a decision to fly on a Delta. Only limited choices existed. Scout payload capability, on the order of 250 kg to low orbit, was considered too restrictive for an experimental flight lest in which prudence dictated that mass might be used to ameliorate technical and schedule difficulties. Initial discussions with government and industry officials showed essentially full manifests for existing Titan- and Atlas-family vehicles. In contrast. the Delta program had at that point three essentially complete and unmanifested vehicles with a payload capacity in the 3000 kg range and which could be made available to SDIO.

A total of 381 fragments of 10 cm or greater were generated by this hypervelocity impact. Additionally, Capt Stephen K. Remillard, USAF, theorized thousands of fragments 1 cm or less will be produced in such collisions. Specifically, he states the following: "When a projectile collides with a satellite at orbital velocities, the outcome of the collision is determined largely by the relative masses of the projectile and target. If the projectile and target are roughly the same size (within a factor of 100) a catastrophic collision will result. This means that all of the target and all of the projectiles are converted to debris. Otherwise, some amount of debris will be generated as a function of the mass and velocity of the projectile. A more massive, or faster moving, projectile will generate more debris, all other factors being equal. The detailed calculations of a notional ASAT attack predict approximately 40,000-70,000 pieces of debris (less than 1 cm) could be generated depending on relative size, speed and orientation of attack, as well as spacecraft design features such as component positioning and materials." Source: Stephen K. Remillard, "Debris Production in Hypervelocity Impact ASAT Engagements," Thesis for Master of Science (Space Operations) at Air Force Institute of Technology (Wright-Patterson AFB, OH: 30 November 1990): 14.

Delta 180 received a presidential citation, two DoD distinguished public service medals, and awards from the American Institute of Aeronautics and Astronautics (AIAA), the American Defense Preparedness Association, and Aviation Week & Space Technology magazine. It was even popularized in Reader's Digest.

Six current and/or former staff members, of the Johns Hopkins University Applied Physics Laboratory (APL), in Laurel, Md., were presented the first-ever Technology Pioneer Award by the Missile Defense Agency on March 24, 2006. APL team members recognized for their efforts during 1984-1986 include: current Space Department employees, Larry Crawford, department head and former Delta 180 aircraft instrumentation manager; Courtney Ray, a former lead analyst for Delta 180; and Thomas Coughlin, then Delta 180 APL science module program manager; and former employees, John Dassoulas (retired), former APL Delta 180 program manager; Michael Griffin, current NASA administrator and former head of APL's Space Department, and then APL's Delta 180 systems engineer; and Thomas Roche (retired), then Delta 180 payload integration and testing lead.