PREPARED STATEMENT OF MILTON KLEIN, MANAGER, SPACE NUCLEAR SYSTEMS OFFICE, NATIONAL AERONAUTICS AND SPACE AD

MINISTRATION

INTRODUCTION

Mr. Chairman, Members of the Committee:

I appreciate this opportunity to discuss the work of the National Aeronautics and Space Administration and the Atomic Energy Commission in the nuclear rocket program, the development of nuclear power for space applications, and basic research in electrophysics which will advance the technology of both space power and propulsion.

In the pursuit of National goals for the exploration and application of space technology for the benefit of mankind, nuclear energy will play an ever-increasing role in providing power and propulsion. Nuclear systems are capable of producing vast quantities of energy in relatively compact, light-weight packages. As this Committee has long recognized, with proper technologies and engineering approaches, this source of energy can provide power for spacecraft voyaging long distances and for long times in space. In addition, nuclear energy for propulsion makes it possible to conceive economical space transportation systems and perform missions not possible or practical with conventional systems.

Significant progress has been made in the programs of research, technology, and the development of flight systems. We have already seen demonstrations of the value of some nuclear systems to space flight missions, e.g., isotope power units for the Nimbus satellite and the Apollo 12 and 14 lunar surface experiments. In addition, progress in nuclear rocket technology has fostered development of the NERVA flight engine beginning in 1969 and continuing, although at a minimum level, in FY 1971. We have completed the baseline engine design and initiated detailed design and development of components. Limited research and advanced technology studies in both the power and propulsion areas show the potential for even higher performance nuclear systems.

In the overall sense, therefore, our programs to apply nuclear energy to the exploration of the frontiers of space are on a sound technical footing; they are ready to continue into development of systems for a variety of applications. However, the overall National interest has led to a stretched out program in space, and as a result, the expected timing of the potential mission applications for some of the nuclear systems has been deferred to a later time period than previously anticipated. This situation has led to a slow-down in FY 1972 of several of the space nuclear development and supporting technology activities. In the nuclear rocket program, NERVA and supporting technology activities will continue, but at a reduced pace in FY 1972, retaining a core of capabilities in the principal organizations involved in the program. Maintaining these capabilites is vital to permit continual progress toward attainment of the NERVA and other advanced propulsion objectives by taking advantage of the experience gained from more than 10 years of scientific and technical contributions.

Continuation of NERVA development is essential to the Nation's future in space. Beginning in the early 1980's a number of mission classes will benefit significantly from the availability of the NERVA engine. It will be the propulsion system used for translunar transportation when it becomes appropriate to resume a program of manned lunar exploration. NERVA can provide the means for extensive exploration of the entire solar system with automated spacecraft. And it can also move large payloads from a low orbit to synchronous orbit and shift spacecraft from one orbital plane to another.

In the power area, full support is maintained for those programs for delivery of radioisotope thermoelectric generators for approved and near-term applications. These include the Pioneer and Viking for NASA, the Transit navigational satellite for the Navy, and the multi-hundred watt needs of a prospective DOD Satellite experiment and NASA outer planet missions. The zirconium hydride power reactor program has been reduced in level so that fabrication of a reactor for future system development and combined testing (288)

with the power conversion system will be delayed while a core of capability is retained in fuel element R&D and system design. In addition, the thermionic reactor program will continue the vital work to establish the required fuel element technology, though plans to proceed with construction of a reactor experiment are deferred.

The actions taken to slow down several programs are necessary because of budget limitations, and do not reflect less interest in the capabilities offered by nuclear propulsion and power. NASA views advancements in power and propulsion of the highest priority among the space technologies in the long view of the space program. No other technology has emerged to make the nuclear activities obsolete or to supplant them. Indeed, nuclear power and propulsion remain the only known way of achieving these advancements.

Before discussing these programs in detail, I would like to note the organizational changes made last October with respect to the management of space nuclear power programs. NASA and AEC have agreed that all space nuclear power activities of each agency be combined in a single joint organization. Further, it was agreed by NASA and AEC that the existing joint office, Space Nuclear Propulsion Office (SNPO), be expanded to include not only the nuclear rocket program but also the nuclear space power and related power conversion program elements of the respective agencies. The name of this joint office is the Space Nuclear Systems Office (SNSO).

NUCLEAR ROCKET PROPULSION PROGRAM

The nuclear rocket program has, for the past two years, involved the development of the NERVA flight rated engine for a variety of space flight missions. This flight engine development is based on many years of scientific and technical progress. Continuing research and technology activities are also conducted to support NERVA development, to provide essential nuclear stage technology, and to explore novel concepts for applying both fission and fusion to propulsion. Before proceeding with a description of the program in detail, the impact of the FY 1972 budget on the nuclear rocket program should be discussed. For FY 1972, the pace of the NERVA development project and the supporting technology activities will be reduced because of budgetary constraints and the expected timing of applicable missions. Although not conducted at the optimum pace, NERVA development will be continued, retaining a core of capability which can grow into full development at the appropriate time.

The funding level in FY 1972 is intended to retain a core of capability within the Aerojet Nuclear Systems Company, the Westinghouse Astronuclear Laboratory and the Los Alamos Scientific Laboratory. These are the principal contributors to NERVA development and supporting activities. Employment levels in these organizations, however, must be reduced substantially below the current manpower assigned to the program. Some limited NERVA engine component and Nuclear Furnace testing will be possible in some of the Nuclear Rocket Development Station facilities, but others of these unique facilities will be placed on standby for future use. With the resources available to us, we expect to continue research and development on some of the critical components having the longest development lead times.

NERVA APPLICATIONS

The NERVA engine is the only practical advanced propulsion system which can be made available to meet the requirements of missions in prospect for the 1980's. You will recall the statements of the past year regarding the proposed space transportation system. One element of this system is a space shuttle to deliver payloads at low cost to an orbit about the Earth. Another major element is a NERVA-powered nuclear stage to go beyond the orbital range of the space shuttle. The high specific impulse of the NERVA engine, with the potential for further performance growth, makes it a flexible, economical propulsion system for a wide range of applications.

When it becomes appropriate to resume manned lunar exploration after the Apollo program is completed, a system with the capability of the NERVA engine will be needed to transport men and equipment to and from the moon (fig. 1, NASA NSO 71-3453). The NERVA-propelled nuclear stage could provide transportation of automated spacecraft for exploration of the surfaces of Mars, Venus, Mercury, some of the moons of Jupiter and certain asteroids. The return of samples to the Earth will be possible in some cases. In addition, the nuclear

stage could send spacecraft on fast trips to the distant planets, reducing trip times by several years in comparison to other propulsion units. Another application would likely be to move large payloads between low and synchronous orbits or from one orbital plane to another. It is expected that at least some of these missions will occur early in the 1980's. In fact, it is possible that nearly all complex missions beyond those in low orbit could be planned around the use of the NERVA stage in much the same manner that the space shuttle is considered to be the launch vehicle for virtually all purposes.

Another potential use for the NERVA engine or its technology could be in support of military missions. Although we are not aware of any specific applications at the present time, experience tells us that our Nation's security rests in part on advancements in technology and their application to military systems.

LUNAR SHUTTLE APPLICATIONS

Last year we discussed typical orbit-to-orbit mission applications of the nuclearpropelled vehicle with circular Earth orbit as the mission starting point. We discussed vehicles with large single propellant tanks which could be launched into Earth orbit with the Intermediate-21 or an equivalent disposable launch vehicle and then reloaded with propellant by space shuttle flights. We only briefly reported on early results of studies of vehicle configurations which might be launched by the space shuttle.

As we have continued these studies, we have found that modular vehicles, for launch by the shuttle, are particularly versatile since the size of the vehicle can be changed to fit many types of lunar and planetary science missions by simply varying the number of propellant modules (fig. 2, NASA NPO 70–369).

A typical use of the nuclear vehicle in the reusable orbit-to-orbit mode would be in support of manned lunar operations in which lunar stations or bases, equipment and supplies are delivered from Earth orbit to the lunar vicinity and personnel are rotated on a regular basis. A nuclear vehicle with a usable propellant capacity of 305,000 pounds (8 propellant modules) would support a minimum manned lunar program with an average of six flights per year. Our latest analysis shows that such a vehicle could carry an outbound payload of 121.000 pounds and return with 27.000 pounds. The corresponding vehicle weight upon departing Earth orbit would be about 510.000 pounds. This same vehicle could transport 175.000 pounds one way from earth orbit to lunar orbit with no return payload. A two-stage chemical vehicle capable of supporting the same lunar program would require a total usable propellant of 520 000 pounds; the corresponding Earth-orbit departure weight would be nearly 705,000 pounds.

SOLAR SYSTEM EXPLORATION WITH NERVA ENGINE AND Stage

The nuclear stage concept formed by assembling shuttle-launched propellant tanks has some interesting prospects for conducting missions to explore the solar system with automated spacecraft. First, the system could be made available to perform prospective energetic missions in the early 1980's. Second, the nuclear stage could be tailored to suit the mission requirements of payload and energy by choosing the number of propellant tanks needed. Third, the NERVA engine could be operated at high specific impulse since short operating times would be required. (This advantage was not included in the following mission analyses.) Fourth, additional performance gains can be achieved by disposing of propellant tanks as they are emptied. The sum of all these features is a propulsion system that is flexible and economical with the capability to perform a range of missions, including very demanding ones.

One mission we have examined is the return of samples from the surface of Mars by means of an automated spacecraft. A nuclear stage configuration consisting of 5 propellant tanks can deliver a payload of 35,000-65,000 pounds into orbit around Mars. This payload would allow 160-240 pounds of material to be selected by roving vehicles from two or three different locales of the Martian surface for return to Earth. The mission duration would be about 600 days.

Studies of sample return missions from other bodies in the solar system are in process or planned. Preliminary results show that the nuclear stage described above could make it possible to recover samples of the Venusian atmosphere (if not the surface), of the surface of Mercury, and of many asteroids.

Another interesting application for the reusable nuclear stage would be to deliver orbiting automated laboratories to the distant planets. A preliminary study of such missions shows that the NERVA-propelled stage of only 4 propel

lant tanks could carry 6000 pounds of payload to an orbit about Jupiter on a trajectory that consumes only 450 days of travel time. Analysis of this mission using a nuclear electric propulsion unit in the 50-100 Kw power range provides the following result: a payload of about 4000 pounds in orbit around Jupiter can be achieved but only for a trip time of 800-1000 days, depending on the power plant specific weight assumed in the calculation. The transportation costs for either case could be approximately equal; however, the short trip-time of the nuclear rocket is much preferred for the sake of an increase in probability of mission success and to speed the return of data to the scientific investigators. Short trips to the planets beyond Jupiter would also be much desired. The NERVA-propelled stage could deliver about 4000 pounds of spacecraft to Nepture in approximately 6.5 years on a direct flight and in 4.8 years with an assist from a Jupiter swingby, a performance capability comparable to a 100-kilowatt electric propulsion system having a specific weight in the range of 30 kilograms per kilowatt, and much greater than any existing chemical system.

In addition to this propulsion capability, it appears that the NERVA engine could also be designed, if desired, to provide from 15 to 25 kilowatts of electrical power for long periods of time. A study managed by Marshall Space Flight Center has described a technique for generating this much power from the NERVA reactor with only relatively straightforward modifications in the basic engine and with little or no extension of power conversion technology. In the power generating mode, the NERVA reactor would be operated at low power levels (200 kilowatts) and low temperatures. A separate flow-loop through the reflector region would carry the energy from the reactor to a power conversion unit. In addition to providing power, this kind of system would reduce and simplify the afterheat removal from the NERVA reactor following operation in the highpower, rocket-engine mode.

NERVA ENGINE DEVELOPMENT

OVERALL STATUS AND PLANS

During this past year the design of the NERVA engine has proceeded on schedule. We have completed the baseline design and have nearly completed the formal design review. The design baseline and specifications for the overall engine and nuclear subsystem have been thoroughly documented in accordance with the strict systems engineering approach we are employing.

The resulting overall engine design is pictured in a photograph of the engine mockup on figure 3 (NASA 71-3473). The engine configuration, size and performance are as described last year. The thrust will be 75,000 pounds and the specific impulse 825 seconds. The engine will be highly reliable and safe in operation due to the use of very conservative design and employment of a high degree of redundancy in the moving parts such as valves and turbines. The endurance goal is 10 hours and the engine will be capable of many start and stop cycles.

Figure 4 (NASA NSO 71-3472) illustrates the systems engineering approach being used for the NERVA engine design. The design starts with the establishment of requirements and then in orderly sequence proceeds through the steps of developing functional requirements, allocating those requirements to specific components or systems, conducting design and trade studies to select designs which meet the requirements, developing designs of both the overall system and the components based on the selected concepts, and producing specifications and extensive engineering data to provide the baseline for the development of the engine. All of the activities shown on this chart with the exception of detailed component design and development are finished or scheduled to be finished this fiscal year.

The thoroughness of the work is illustrated by the photograph of the display in figure 5 (NASA NSO 71-3471) of the documentation for the Nuclear Subsystem Preliminary Design Review. The engine design work to date has sustained the validity of the very high performance, reliability and safety that were discussed with you last year.

In the component area we are continuing to conduct an extensive turbopump bearing test and development program. We have completed the design of the turbopump inducer and impeller and have initiated fabrication of the first test units. We have recently completed a test and analysis program in which dual, redundant turbopumps, such as will be used in the NERVA engine, were thoroughly evaluated in startup, steady state, shutdown and various malfunction modes. These tests have shown that the dual turbopump system is stable, controllable, and predictable.