3. FLIGHT EXPERIMENT IMPLEMENTATION

Conducting a life sciences experiment onboard a spacecraft can be a formidable task (Fig. 3-1). Designing experiments, assembling the necessary resources, building the appropriate hardware, conducting innumerable tests and coordinating experiments with missions are time-consuming, complex activities. The entire effort may take from 2 to 10 years, depending on the nature of the experiment and the mission (Fig. 3-2). The need for ground-based control studies to verify the scientific validity of inflight data further complicates the process.

Figure 3-1: The space life science researcher's story from the U.S. Biosatellite era. Adapted from the American Institute of Biological Sciences, Experiment Survey Program, Biosciences, U.C. Berkeley,1968. (Click to enlarge)

     The major activities involved in carrying out an experiment in space are described for two cases. The STS program represents a situation where experiments can be performed in manned spacecraft. In such cases the experiment design, types of animals, hardware used, and preflight and postflight operations must be compatible with crew safety requirements. The Cosmos Program is an example of a situation where experiments can be conducted in an unmanned vehicle. In this case, experiments are not constrained by crew safety standards, but they must rely on automated hardware because inflight crew manipulations are not possible.

Experiments on the Space Transportation System

Preparation of a payload for flight on the STS occurs at three levels: experiment, payload, and mission (Fig. 3-3). Objectives, design, and hardware requirements must first be developed for individual experiments. All of the experiments must then be integrated into a single payload which satisfies the requirements of each experiment. Finally, this payload must be incorporated into a designated mission. This means that the payload must accommodate the constraints set on the mission by other payloads, by the design of the spacecraft, and by crew safety and operation requirements.

Figure 3-2: Life cycle of a typical life science flight experiment from the U.S. Biosatellite era. Adapted from American Institute of Biological Sciences, Experiment Survey Program, Biosciences, U.C. Berkeley, 1968.

     NASA conducts at least three reviews at each preparatory level. These are the Preliminary Requirements Review (PRR), the Preliminary Design Review (PDR), and the Critical Design Review (CDR). Through these reviews NASA maximizes the potential for implementing a successful life sciences experiment in space. The three reviews within a level progressively refine the experiment, payload, or mission. The results of the reviews from one level are fed into the next level of development.

Experiment Development

     Selection

     NASA receives both solicited and unsolicited proposals for flight experiments from researchers in various life sciences disciplines. NASA, or an external agency selected by NASA, evaluates the scientific merit of each proposal through a peer review process. ARC, JSC, or KSC determines the feasibility of conducting each proposed experiment in space. They address engineering and experiment development costs, management requirements, and availability of NASA resources. NASA Headquarters then selects a subset of feasible experiments. This is the candidate pool from which experiments are finally chosen for definition.

     Three major factors are considered when assigningexperiments to a particular mission. First, scientific yield from different research areas has to be maximized. Second, there must be minimal interference between experiments. Finally, maximum use must be made of common facilities, sensor systems and data processing equipment.

     Definition

     Detailed definition of experiment requirements begins after a contract or grant is negotiated between an investigator and NASA. Several issues must be addressed to fully define an experiment (Table 3-1).

     The science objectives of the experiment must be clearly formulated and the feasibility of conducting the experiment in space carefully evaluated. The resources required for developing the experiment must be available. Ground-based operations necessary for conducting the flight experiment, and supporting studies to assess experiment feasibility, must also be defined.

Figure 3-3: Preparation of a payload for a Space Shuttle mission. PRR: initial design formulated. PDR: design reviewed and hardware requirements incorporated. CDR: design finalized and building of flight hardware approved.

     Requirements are updated as the experiment undergoes continuous refinement. Supporting studies are conducted to provide baseline data for each experiment. Such studies are initiated early because they affect the experiment's overall design. If the initial design does not receive NASA concurrence, new approaches are considered.

Hardware

     Hardware must be specially built or modified to suit the space environment. Flight hardware is designed to meet stringent requirements pertaining to safety, mass, mechanical operation, structural features, electrical power usage, computer interfaces, and thermal properties. Safety standards must be verified and meticulously recorded. In addition, all flight hardware must be tested to verify that it can withstand the mechanical and acoustic vibrations encountered during launch, the acceleration forces (up to 3.2 g) during ascent into orbit, and the microgravity conditions in orbit.

     Flight hardware includes equipment for housing the experiment subjects and monitoring their health and general well-being. Individual experiments sometimes require that special hardware be designed and fabricated (experiment unique equipment (EUE)), in addition to general purpose multi-user flight hardware. Hardware prototypes are fabricated during the experiment development phase. They must be compatible with the design and safety requirements of the STS and be able to withstand the stress of launch and re-entry. At the same time, appropriate system interfaces are designed and procedures for instrument verification developed. Prototype hardware designs are reviewed twice before flight hardware is fabricated. Existing ground hardware is also evaluated for potential transition to flight application at this time.

     A formal review is conducted once the experiment and hardware design is completed and formally defined. After acceptance at this review, the experiment is ready to be incorporated into a payload.

Payload Development

Payload development is the process by which individual experiments are combined into a cohesive package. It is analogous to and frequently proceeds in parallel with the experiment development process. The results from individual experiment and hardware reviews provide input to the formal payload review processes.

Science Objectives

  • Hypothesis
  • Experiment Goal
  • Research Subjects

Hardware/Data Requirements

  • Housing for Research Subjects
    • provision of food and water
    • suitable environment
    • waste collection
  • Measurements
    • physiological
    • environmental

Mission Constraints

  • Size of Payload
  • Weight of Payload
  • Power Requirements of Payload
  • Thermal Issues

Safety Considerations

  • Biological Isolation
  • Flammability/Offgassing of Hardware

Equipment/Science Verification Procedures

  • Data Acquisition Capability of Hardware
  • Biocompatibility of Hardware
  • Feasibility and Value of Science
  • Supporting Studies

Operations

  • Crew Training
  • Preflight, In-flight, and Postflight Procedures
  • Ground Support Equipment
  • Logistics

Table 3.1: Issues addressed during development of a flight experiment.

     Flight hardware is developed during this phase. Besides the items that are actually flown on the Shuttle, this hardware includes flight and ground data systems and special ground support equipment, such as checkout equipment for interface verification and functional tests. All flight hardware is subjected to verification testing and formal reviews.

     A payload must undergo testing at the subsystem and system levels. Two main tests are conducted at the system level. The first is a Biocompatibility Test, so called because it is used to assess the compatibility of the hardware with the biological environment (including research subjects). The second is the Experiment Verification Test (EVT), which uses a simulated mission timeline and simulated flight conditions to verify the effective interaction of experimental procedures, hardware, and personnel.

     In addition, the readiness of the payload for integration into a mission must be evaluated before it is shipped to KSC. Once it is demonstrated that the mandatory verification procedures have been performed, the payload is ready for physical integration into the Spacelab or the Shuttle middeck at the launch site.

Training of flight and ground support personnel is an important part of any space flight mission and is often conducted in specialized facilities. These may be equipped with flight hardware mockups, mathematical models, or payload simulators such as the Spacelab simulators provided for crew training at JSC and Marshall Space Flight Center (MSFC).

Payload Integration

Payload reviews generate results which provide input to the reviews held at the mission level. All requirements from various payloads must be combined to ensure mission success. During this period, hardware is fitted into the spacecraft, mission support personnel are acquired, and the crew is trained. The compatibility of the payload with the STS and with other payload elements, and overall system safety must be confirmed. Much of this activity takes place at KSC. ARC's involvement, and that of the investigators, is essential throughout this phase.

Investigator's Role

The investigator plays an important role during the entire payload development phase. Investigator Working Groups are established during the experiment definition phase to coordinate the requirements of different experiments. Investigator input is critical when evaluating the capability of the hardware to meet experiment requirements, and during biocompatibility testing. The investigator must help train crew members to familiarize them with experiment requirements and in-flight procedures. The investigator also assists in evaluating payload design in relation to the defined experiment requirements and in reviewing payload integration and checkout.

     Science support facilities at ARC, KSC, MSFC, and JSC give investigators access to in-flight data while the mission is in progress. These facilities also enable investigators to communicate with crew members during the mission.

Flight Phase

The flight phase begins at launch. Once the spacecraft reaches orbit, crew members follow a minute by minute schedule to accomplish the mission and experiment objectives. During these operations, the crew can consult with investigators via two-way voice communications, air-to-ground telemetry (data transmission), and television.

     In-flight data is displayed simultaneously onboard and in the Science Operations Area at the MSFC. This data can also be transmitted to Test Monitoring Areas at ARC, JSC, KSC, and remote laboratories.

     Operations that take place on the ground during the flight phase are as important as those that occur onboard the spacecraft. The Mission Control Center at JSC is responsible for monitoring and providing contingency support for orbiter payloads, two-way communications with the crew and onboard systems, and transmitting flight data to a central site. It also communicates with the Payload Operations Control Center (POCC) for coordinating flight operations between orbiter and Spacelab payloads. The POCC houses data monitoring facilities and commands payload elements in the Spacelab while maintaining communications with the Mission Control Center and the crew.

Pre/Postflight Operations

Preflight studies are frequently conducted several months before the mission to collect baseline data for flight experiments. Many investigators also require preflight collection of biosamples or data. During this period, investigators use laboratory facilities at various NASA centers to prepare experimental subjects for flight and to take preflight baseline measurements.

     Special facilities are situated at launch and landing sites for harvesting and processing biospecimens, and for preflight data collection. For instance, the Life Sciences Support Facility at KSC is used for preparing and analyzing nonhuman biospecimens. Available resources include common laboratory supplies and analytical instruments, and animal maintenance facilities.

     Experimental subjects are usually loaded into the Spacelab about 30 hours before launch and may be removed from the spacecraft as early as 3 hours after landing. Middeck payloads can be loaded about 18 hours before launch. Data collection commences at a facility situated at the landing site. Special arrangements are made if the orbiter is forced to land at a secondary or contingency site.

Experiments on Cosmos Biosatellites

U.S. scientists have conducted many experiments within the Soviet Cosmos biosatellite program. Experiments on the Cosmos biosatellite differ from those carried out on the Space Shuttle mainly because of one important factor. Since the biosatellite is unmanned, all in-flight experimental operations must be automated, as must all spacecraft subsystems and life support systems for experimental subjects. The biological subjects cannot be directly observed, although video viewing is possible. Repair or manual regulation of the life support system or the experiment hardware is not possible in flight, as are even the simplest of experimental operations. An unmanned satellite, therefore, has special demands for quality and reliability, especially in the equipment that provides automatic control and remote monitoring during the course of the flight experiments. This need for automation places some constraints on the types of experiments that can be performed on the biosatellite. Additionally, extensive shock and vibration testing needs to be carried out because of the impact of landing.

     There are, nevertheless, distinct advantages to using unmanned vehicles for experimentation in space. The overall cost per mission is considerably less than for a manned mission. A wider range of materials can be used in hardware fabrication because crew safety is not a consideration. For the same reason, experiment design is more flexible. Missions can be terminated early if necessary or extended to maximize science return without concern for the requirements of the crew.

Experiment Development

     Selection

     Flight programs are developed by the U.S.S.R./Russia. The forum for presenting these program scenarios is frequently at meetings of the Joint Working Group for Space Biology and Medicine. At these yearly meetings, joint projects are discussed. Experiment proposals are invited from the U.S. and other participating countries. Once proposals are accepted and approved by Russian specialists, plans are exchanged on the best means of implementing the studies.

     Definition

     Experiments submitted by U.S. investigators are conducted jointly with Russian counterparts. Tissue samples and data are frequently shared between the two countries. In some cases, Russian and U.S. investigators perform complementary analyses of flight data, thus enhancing the science of both countries.

     A key document, the Experiment Management Plan, is prepared for each experiment. This plan is a comprehensive summary of the experiment objectives, data, equipment, and operational requirements. It also outlines the agreements made between Russian and U.S. scientists with respect to data sharing and provision of equipment. The document is regularly updated, providing a means for recording the experiment's evolution to a state of readiness for flight.

     Hardware

     On the first three Cosmos missions with U.S. participation, most U.S. experiment hardware was in self-contained packages during the flight. Life support for the experimental subjects was provided mainly by the Soviet spacecraft environmentalcontrol system. These packages were delivered to the U.S.S.R.after flight qualification testing was performed in the U.S. The packages were installed in the spacecraft, flown in Earth orbit, and then returned to the U.S. Rodent and primate housing systems have always been provided by the U.S.S.R. In recent years, hardware development for the Cosmos experiments has become more of a joint effort. From the time of the first primate mission, Cosmos 1514, the U.S. began to supply hardware that required integration with Soviet equipment. On these later missions, U.S.-built hardware was often used to obtain physiological data. Such collaboration demanded joint verification testing and greater cooperation between the two partners.

     U.S. flight hardware is subjected to extensive testing to ascertain that it can withstand launch, space flight, and the impact of biosatellite landing. Although testing is thorough, documentation is kept to a minimum.

Payload Development and Integration

Russia develops and integrates the payload. U.S. representatives are in frequent contact with Russian specialists. Experimental techniques are verified in the U.S. using animal subjects similar to the Russian flight subjects. Training sessions and development of detailed procedures are necessary since Russian and U.S. investigators collaborate closely in many of the preflight and postflight activities. Such activities include sensor implantation, biosampling, tissue preservation, and other experiment operations.

     Complicated logistics and differences in language and metho dology sometimes hinder coordination of Russian and U.S. activities. A true cooperative spirit has been important in circumventing these difficulties.

Investigator's Role

U.S. investigators conducting experiments on the Cosmos biosatellite are not typically involved in mission logistics. Researchers base their experiments on the guidelines of the mission plan provided by the Russians. Investigators conduct preflight testing to ensure thesuitability of techniques and hardware, which is essential to experiment success. In some cases Russian personnel are trained to conduct experimental procedures in the investigator's absence. Investigators frequently travel to Russia before the flight. Although they do not take part in any launch or landing activities, they are able to perform preflight/postflight testing on the flight animals during a certain window of time before launch and after recovery. Biosamples from experiment subjects are processed by U.S. investigators either in Russia or at their own laboratories.

The Flight Phase

In the past, the launch of the biosatellite has been a closed event and participation by foreign representatives has rarely been invited.

     Flight duration is determined by the program of scientific studies. While in orbit, the onboard systems of the satellite operate in accordance with the flight program. Animals are allowed access to food and water according to a specific schedule. An automatic lighting system provides simulated day and night periods. Radio telemetry is used to control the flight subjects' environment and the spacecraft systems. Russian ground stations track the path of the biosatellite.

Pre/Postflight Operations

Preflight studies are conducted in the U.S. several months before the launch. U.S. investigators conduct some limited preflight and postflight operations, but in most cases Russian specialists handle flight animals.

     Unlike the Space Shuttle, the Cosmos biosatellite does not land at a specific site. An automatic landing system controls the descent of the biosatellite's landing module. As the module moves through the Earth's atmosphere, a parachute system becomes operational, which cushions the impact of landing. Radio direction finding equipment is used to locate the biosatellite.

     Once the biological subjects are recovered, immediate postflight operations are conducted in a temperature-controlled field laboratory erected at the landing site. Primates are examined upon recovery and then shipped to Moscow for testing.

     Processing of other biospecimens begins three or four hours after landing. Tissue samples requested by U.S. investigators are preserved or frozen according to instructions, and later shipped to the U.S. If required, postflight testing is performed after the subjects have been transported to Moscow.

Move to next section 4. Programs, Missions, and Payloads

Additional Reading

American Institute of Biological Sciences. Experiment Survey Program. Biosciences, U.C. Berkeley, 1968.

Ballard, R.W. and K.R. Walker. Flying U.S. Science on the U.S.S.R. Cosmos Biosatellites. American Society for Gravitational and Space Biology Bulletin, vol. 6, no. 1, October 1992, pp. 121-128.

Hypen, W. and J.C. Casas. Flying a Scientific Experiment Aboard the Space Shuttle - A Perspective from the Viewpoint of the Experimenter, unpublished report.

Ilyin, E.A. and G.P. Parfenov. Biologicheskiye Issledovaniya na Biosputnikakh 'Kosmos' (Biological Studies on the Cosmos Biosatellite). Nauka Publishing House, Moscow, in Russian, 1979.

Mains, R.C. and E.W. Gomersall. U.S. Monkey and Rat Experiments Flown on the Soviet Satellite Cosmos 1514. NASA TM-88223, May 1986.

NASA. Guide to the Life Sciences Flight Experiments Program. NASA Life Sciences Flight Programs Branch, Washington, D.C., unpublished report, July 1984.

NASA. STS Investigator's Guide. NASA Marshall Space Flight Center, unpublished report.

Souza, K.A., P. Davies, and K.R. Walker. Considerations for Life Science Experimentation on the Space Shuttle. American Society for Gravitational and Space Biology Bulletin, vol. 6, no. 1, October 1992, pp. 129-136.