When the President offered his new vision for space exploration in January of 2004, he said, "Our third goal is to return to the moon by 2020, as the launching point for missions beyond," and, "With the experience and knowledge gained on the moon, we will then be ready to take the next steps of space exploration: human missions to Mars and to worlds beyond." A human mission to Mars implies the need to move large payloads as rapidly as possible, in an efficient and cost-effective manner. Furthermore, with the scientific advancements possible with Project Prometheus and its Jupiter Icy Moons Orbiter (JIMO), (these use electric propulsion), there is a renewed interest in deep space exploration propulsion systems. According to many mission analyses, nuclear thermal propulsion (NTP), with its relatively high thrust and high specific impulse, is a serious candidate for such missions. Nuclear rockets utilize fission energy to heat a reactor core to very high temperatures. Hydrogen gas flowing through the core then becomes superheated and exits the engine at very high exhaust velocities. The combination of temperature and low molecular weight results in an engine with specific impulses above 900 seconds. This is almost twice the performance of the LOX/LH2 space shuttle engines, and the impact of this performance would be to reduce the trip time of a manned Mars mission from the 2.5 years, possible with chemical engines, to about 12-14 months

Kirk, Daniel R.

NASA Technical Reports Server

   
2004 
 
NASA FACULTY FELLOWSHIP PROGRAM 
 
 
 
 
MARSHALL SPACE FLIGHT CENTER 
 
THE UNIVERSITY OF ALABAMA  
THE UNIVERSITY OF ALABAMA IN HUNTSVILLE 
ALABAMA A&M UNIVERSITY 
 
 
 
 
 
MODELING AND TESTING OF NON-NUCLEAR, HIGH-
POWER SIMULATED NUCLEAR THERMAL ROCKET 
REACTOR ELEMENTS 
 
 
 
 
 
 
Prepared By:     Daniel R. Kirk 
 
Academic Rank:    Assistant Professor 
 
Institution and Department:   Florida Institute of Technology 
Mechanical and Aerospace 
Engineering Department   
         
NASA/MSFC Directorate:   Transportation 
 
MSFC Colleague:    Dr. Charles Schafer 
 
 
XXIV-1 
https://ntrs.nasa.gov/search.jsp?R=20050215304 2019-08-29T19:47:54+00:00Z
   
Introduction 
 
When the President offered his new vision for space exploration in January of 2004, he said, 
“Our third goal is to return to the moon by 2020, as the launching point for missions beyond,” 
and, “With the experience and knowledge gained on the moon, we will then be ready to take the 
next steps of space exploration: human missions to Mars and to worlds beyond.” A human 
mission to Mars implies the need to move large payloads as rapidly as possible, in an efficient 
and cost-effective manner. Furthermore, with the scientific advancements possible with Project 
Prometheus and its Jupiter Icy Moons Orbiter (JIMO), (these use electric propulsion), there is a 
renewed interest in deep space exploration propulsion systems. According to many mission 
analyses, nuclear thermal propulsion (NTP), with its relatively high thrust and high specific 
impulse, is a serious candidate for such missions. 
 
Nuclear rockets utilize fission energy to heat a reactor core to very high temperatures. Hydrogen 
gas flowing through the core then becomes superheated and exits the engine at very high exhaust 
velocities. The combination of temperature and low molecular weight results in an engine with 
specific impulses above 900 seconds. This is almost twice the performance of the LOX/LH2 
space shuttle engines, and the impact of this performance would be to reduce the trip time of a 
manned Mars mission from the 2.5 years, possible with chemical engines, to about 12-14 
months, [1, 3, 4, 6, 8, 11, 17, 23]. 
 
Nuclear rocket engines are not a new concept, and were designed, built and tested under the 
Rover/NERVA (Nuclear Engine for Rocket Vehicle Applications) program from 1956-1972, but 
were never implemented into the space program. An excellent summary of the Rover/NERVA 
program is given in Reference [8], with many more details about the program contained in 
References [1, 4, 7, 23, 26]. An example of a nuclear thermal rocket and cross-section of the 
reactor core developed during the NERVA project are depicted in Figure 1. Many of the reactor 
and system concepts that are the subject of contemporary interest are similar to those depicted in 
Figure 1, although new advancements in materials fabrication and geometries have arisen since 
the NERVA Project, [3, 21, 23, 25]. Unfortunately, despite the nearly $10 billion (1992 constant 
dollars) invested, the promises of aerospace nuclear propulsion remained unrealized. The past 
four decades have witnessed repeated episodes in which nuclear propulsion projects are initiated 
and development and testing take place, only to be followed by growing doubts about the merit 
or utility of the proposed applications, and ultimately the project's cancellation. However, with a 
new, energetic, clearly thought out vision for space exploration, NTP may finally prove itself a 
“superior capability in the space domain” and “the day is not far off when nuclear rockets will 
prove feasible for space flight,” [6]. 
 
The work presented herein qualitatively and quantitatively defines a non-nuclear test program to 
characterize the heat transfer processes attendant to a single fuel-element, and a single cooling 
channel in a nuclear thermal rocket. A model employing the current understanding of heat 
transfer processes taking place within the reactor core has been developed to facilitate the design 
of an experimental test bed. The goal of the experiment is to provide NASA MSFC with a 
capability for assessing and evaluating candidate NTP materials over a range of conditions 
relevant to nuclear rocket missions.  
XXIV-2 
   
 
 
 
 
 
Figure 1: Typical Rover/NERVA Nuclear Reactor Configuration and Core Cross-Section. 
 
As indicated in Reference [17], “One of the key questions that has arisen… is [how] to test a 
nuclear rocket engine in the current societal environment. Unlike the Rover/NERVA programs in 
the 1960’s, the rocket exhaust can no longer be vented to the open atmosphere.” Additionally, 
since the nuclear and heat transfer processes taking place within a NTP device are essentially 
decoupled, there exists compelling motivation to learn as much as possible through a non-nuclear 
test program. Such non-nuclear experiments would be a safe, cost-effective, and beneficial 
precursor to nuclear testing. 
 
Heat Transfer and Fluid Dynamics Modeling Results
 
Among the research issues attendant to the development of a nuclear thermal rocket engine is the 
need to have a detailed understanding of the high temperature, high power heat transfer issues 
associated with extracting thermal energy from a nuclear power source with hydrogen as the 
XXIV-3 
   
working fluid. An important first step in gaining this understanding is developing analytical 
models of simulated nuclear thermal reactor cooling elements to help understand the heat 
transfer processes taking place. Furthermore, it is critical to accurately model the hydrogen 
thermal and transport properties at these elevated temperatures and pressures, [18, 19, 20, 22, 
24]. An example of results from a model, which simulates the heat transfer mechanisms taking 
place in a typical cooling channel, is depicted in Figure 2. The upper figure illustrates reactor 
power distribution as a function of axial location along (solid line) and the integrated power level 
versus axial position along the reactor (dashed line). The integrated power level is computed 
from reference data, [1, 3, 8, 11] for a single element, single cooling channel by taking the total 
reactor power and dividing by the number of cooling holes. This value is then used as an input 
for actual reactor power distribution based on reactor physics. For the case examined here, a 5 
GW reactor was selected, with an equivalent power per cooling channel of about 55 kW. 
 
Figure 2: Example of Heat Transfer Model Results for a Single Cooling Channel of a 
NERVA-Type NTP Rocket 
 
The lower plot depicts the H2 coolant/propellant temperature and the inner wall temperature. The 
location of the maximum H2 temperature is at the exit of the channel, whereas the maximum wall 
temperature is typically located about 80 percent downstream. Also shown are the location and 
value of the maximum axial gradients in coolant temperature and in wall temperature, and the 
location of the maximum axial difference between the wall and fluid temperatures. Both of these 
regions have experienced material failures in prior NERVA experiments, and are important to 
capture in an experimental simulation. 
XXIV-4 
   
 
Experimental Design Considerations 
 
Although the ultimate goal of the experiment is to investigate candidate nuclear materials in hot 
ydrogen flow, the use of hot hydrogen introduces handling, safety and cost issues that must be 
equirements of an experiment with flowing hot hydrogen, a series of 
reliminary safety, storage, handling and venting concerns were addressed. Fortunately, 
esearch 
aboratory. The simulated elements will be housed in a 2 m long and 23 cm diameter cooled 
h
carefully addressed. Significant knowledge may be gained through the use of inert, surrogate test 
gases such as helium, nitrogen and argon. In such experiments, non-dimensional temperatures 
and heat transfer coefficients may be matched with actual hot hydrogen tests and the behavior of 
materials and the physical processes taking place at these evaluated conditions may be explored, 
[9, 18]. Validation of data acquisition, instrumentation and diagnostic capabilities of the facility 
can be completed prior to the additional complexities associated with hot hydrogen. Furthermore, 
less costly test articles, made of materials such as steel or tantalum, which do not have to be 
impervious to hydrogen, may be utilized. A model to provide the appropriate scaling parameters 
(mass flow, geometry, power settings, pressure, etc.) was developed to guide a test program 
using substitute fluids. 
 
In order to meet the r
p
preliminary tests will utilize relatively low flow rates of hydrogen (1-2 g/s) and will not require 
additional complexities such as a dedicated storage facility, post-test hydrogen collection or burn 
stacks. Readily available, standard bottles will be utilized for preliminary investigations. 
 
The experiment will be located in a 15 x 15 x 10 m dedicated test cell at the Propulsion R
L
vacuum chamber, which contains multiple viewing and instrumentation ports. Due to elongation 
of the test article at high temperature, bellows fittings to relieve thermal expansion stresses will 
be located at each end. A 100 kW inductive heating system, which is available at the PRL, will 
be utilized to generate the intense thermal boundary conditions. Heating coils will be designed to 
provide a power input profile similar to that shown in the upper diagram of Figure 2 (recall that 
each cooling channel removes ~ 55 kW from the reactor), [27]. Because of the thermal molecular 
and transport properties of argon, an entire cooling element (19 cooling holes) may be simulated 
at these power levels at actual temperatures and heat fluxes. Diagnostics for temperature 
measurement will include non-intrusive optical pyrometers, which are capable of measuring 
external and internal surface temperatures along axial locations of the test article. 
 
Future Applications for the PRC 
 
The data obtained from these experiments will be utilized to gain valuable knowledge about the 
eat transfer processes taking places at elevated temperatures and pressures. The proposed h
experiment will be the first ever to operate at such extreme thermal conditions and large length-
to-diameter ratios (L/D~500) with hot hydrogen flow. The data will be compared with known 
convective heat transfer correlations and appropriate coefficients will be determined. 
Furthermore, valuable data about materials integrity and suitability as a reactor fuel will be 
gained. The structural degradation and mass loss impact due to flowing hot hydrogen on 
XXIV-5 
   
candidate materials will also be assessed. These data will be critical in guiding the design of a 
next generation nuclear thermal rocket system. 
Resources 
 
ed MATLAB for the heat transfer and fluid mechanic analyses, as well as for 
stablishment of a hot hydrogen database. Numerous texts, reports, publications, workshop 
onclusion
This project utiliz
e
summaries, etc. were used to establish a technical and historical context of previous NTP 
technologies and to form the reference comparison cases. Expertise and exchange of ideas from 
several MSFC directorates (TD 06, TD 40, SD 46, and ED 33) was established to foster 
collaboration and expedite specification of appropriate diagnostic and instrumentation.  
 
C  
on Research Laboratory at NASA Marshall Space Flight Center is uniquely suited 
 lead in the development of a next generation nuclear thermal rocket engine. To facilitate this 
ledgments
 
The Propulsi
to
process, a non-nuclear, safe, cost-effective experimental program has been developed with the 
ultimate goal of providing valuable information on heat transfer and material properties in a 
flowing hot hydrogen environment. When completed, the experiment will be capable of 
simulating conditions inherent to NTP systems, but never before investigated in a laboratory 
setting. 
 
Acknow  
e to thank Dr. Charles Schafer, Dr. William Emrich, Harold Gerrish, and 
r. Stephen Rodgers, as well as the entire team of engineers and scientists at the Propulsion 
 
The author would lik
D
Research Laboratory. Additionally, the advice and expertise in the areas of materials science and 
diagnostics from Dr. Binayak Panda and Dr. Jan Rogers is very much appreciated. I look forward 
to working with each of you in the future to bring this promising experiment to fruition. Finally, 
sincere gratitude to Dr. Michael Freeman, Dr. Razi Hassan, Dr. Gerald Karr, and Dr. Jeanelle 
Bland Day for their superior efforts in directing and coordinating the NASA Summer Faculty 
Fellowship Program. 
 
Selected References 
 
1. Angelo, J.A., and Buden, D., Space Nuclear Power. Orbit Book Company. © 1985. 
. Anghaie, S. Personnel Communication at NASA MSFC on July 20, 2004. 
lsion for 
6. Crouch, H.F., Nuclear Space Propulsion. © 1965, Astronuclear Press. 
2
3. Blevins, J.A., Patton, B., Rhys, N.O., Schmidt, G.R., “Limitations of Nuclear Propu
Earth to Orbit,” AIAA 2001-3515. 
4. Bussard, R.W. and DeLauer, R.D., Fundamentals of Nuclear Flight. © 1965, McGraw-Hill, 
Inc. 
5. CHEMKIN Collection III: Thermodynamic Database User Manual. 
XXIV-6 
   
7. El-Genk, M.S., A Critical Review of Space Nuclear Power and Propulsion. American 
8. Fin ocket Engine Program: Overview of Rover engine Tests, 
9. Fow rements of the Heat Transfer Coefficients for 
10. Fur are-Lattice 
11. Given, J.A. and Anghaie, S., “A Computational Model For Thermal Fluid Design Analysis of 
12. Gla ational 
13. Hil n, C., Mechanics and Thermodynamics of Propulsion. 2  Edition, © 
14. How easibility of a Nuclear Rocket for a 
15. How isk to Humans in Planetary 
16. Howe, S.D., “Reducing the Risk to Mars: The Gas Core Nuclear Rocket.” Los Alamos 
17. Howe, S.D., Travis, B., and Zerkle, D.K., “SAFE Testing Nuclear Rockets Economically,” 
18. Inc oduction to Heat Transfer. 2  Edition, © 1990, John 
19. Kin ion of Thermodynamic Properties, Transport Properties, and 
20. Kub n 
21. Law Rocket Propulsion Systems. Space 
22. McCarty, R.D., “Hydrogen Technological Survey – Thermophysical Properties,” NASA SP-
23. Nuc l Propulsion: A Joint NASA/DOE/DOD Workshop. NASA Conference 
24. Pat c Properties and Theoretical Rocker Performance of Hydrogen 
25. Pow ines for New and Unique 
26. Sch  Guidebook for the Application of Space Nuclear Power Systems. 
27. Zin ic Design and 
Institute of Physics. © 1994. 
seth, J.L., “Rover Nuclear R
Final Report,” Contract NAS 8-37814. 
ler, J.M. and Warner, C.F., “Measu
Hydrogen Flowing in a Heated Tube.” ARS Journal, p.266-267, March 1960. 
man, E. "Thermal Hydraulic Design Analysis of Ternary Carbide Fueled Squ
Honeycomb Nuclear Rocket Engine," in 16th Symposium on Space Nuclear Power and 
Propulsion, edited by M.S. El-Genk et al., New York, AIP Conference Proceedings, 
1999. 
Nuclear Thermal Rockets,” Nuclear Technology, Vol. 117, Jan. 1997, pp. 87-108. 
sstone, S. and Sesonske, A., Nuclear Reactor Engineering. ©, 1967, Litton Educ
Publishing, Inc. 
l, P. and Peterso nd
1992, Addison-Wesley Publishing Company, Inc. 
e, S.D., “Assessment of the Advantages and F
Manned Mars Mission,” Proceedings from Manned Mars Mission Workshop, Marshall 
Space Flight Center, Huntsville, Alabama. June 10-14, 1985. 
e, S.D., “High Energy Density Propulsion – Reducing the R
Exploration.” 
National Laboratory. 
Los Alamos National Laboratory.  
ropera, F.P., and De Witt, D.P., Intr nd
Wiley & Sons, Inc.  
g, C.R., “Compilat
Theoretical Rocket Performance of Gaseous Hydrogen.” NASA TN D-275. April 1960. 
in, R.F. and Presley, L.L, “Thermodynamic Properties and Mollier Chart for Hydroge
from 300 °K to 20,000 °K.” NASA SP-3002. 1964.  
rence, T.J., Witter, J.K., Humble, R.W., Nuclear 
Propulsion Analysis and Design, Chapter 8. 
3089, 1975. 
lear Therma
Publication 10079. 1991. 
ch, R.W., “Thermodynami
to 100,000 K and 1.01325x108 N/m2.” NASA SP-3069. 1971. 
ell, J., et al., “MITEE: An Ultra Lightweight Nuclear Eng
Planetary Science and Exploration Missions,” Plus Ultra Technologies, Inc. Report No. 
PUR-1, July 24, 1998. 
midt, H.R. (Chairman),
Report of the Committee on The Nuclear Space Program. January 1969. 
n, S., and Semiatin, S. L., “Coil Design and Fabrication: Bas
Modifications.” Journal of Heat Treating. June 1988, p.32-36. 
XXIV-7 


Modeling and Testing of Non-Nuclear, Highpower Simulated Nuclear Thermal Rocket Reactor Elements

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server