# Presentation: 691210

## NASA’s Nuclear Systems InitiativeOverview

## Nuclear Systems Initiative (NSI)

- Three components to this technology initiative
- Radioisotope power development for potential use on Mars ‘09 and planetary exploration
- Nuclear Fission Electric Propulsion research
- Nuclear Fission Power research
- This initiative is in addition to the In-Space Propulsion Program already in the baseline

**The Nuclear Systems Initiative will enable a new ****strategic approach to planetary exploration and is likely  to play a key role in NASA’s future**

## Nuclear Systems Enabling NASA’s Quest for Life

*RPS capabilities enable the search for life’s origins on Mars*
* **Enhance surface mobility*
* **Increased operational options: full-time science exploration*
* **More advanced instruments*
* **Longer life: more sites, more options, greater diversity ** *

*Fission power and propulsion enables exploration not otherwise possible*
* **Orbiting -- as opposed to fly-by -- missions*
* **Abundant power in deep space: more capable **	**	**instruments, much greater data rates*
* **Reduced trip time: fast science return*
* **Multiple sites and sample return options**  *

## Challenges of Solar System Exploration Beyond Mars

- Giant planet/ring/satellite/   magnetosphere systems
- Pluto/Charon and the Kuiper belt

*Distance*

*Environmental extremes*

*Dynamic systems*

- New types of science and systematic study of multiple targets & processes

- Solar power is impractical
- Flight times are long and gravity assist opportunities can be rare
- Mass is limited, data rates are low

- Radiation and temperature
- Atmospheric and subsurface conditions
- Particle hazards

*Power is essential to meet these challenges...*

_*Characteristic*_

_*Challenge*_

_*What we need:*_

- Power where it’s needed
- Highly efficient electric propulsion
- Increased payload/data return

- Increased mass for shielding and heat for thermal control
- Robust mission and system designs that avoid or tolerate hazardous regions

## Power is ENERGY for science, mobility, playback, etc.

**Power is TIME for surface reconnaissance & discovery**
**Power is ACCESSIBILITY to the planet (latitude, terrain)**
**Power is RESILIENCY and ADAPTABILITY**

**The 2009 Mobile Surface Laboratory Mission:**
- Search for evidence of life (hospitable environments, organics, etc.)
- RPS delivers the capabilities and **TIME** to maximize science yield

**Baseline 180 days (daytime only)**
**Equatorial landing site**
**“****Hostage to time” and power management**
**Yield is 10’s of sensor suite analyses**

**Solar**

**RPS**

**Continuous power for 1000+ days **
**Landing anywhere, any season**
**Time and power to test the “right stuff”**
**Yield is order of magnitude greater (# of analyses, images, distance)**

- Why Does Power Matter?

## Accessible Areas: Solar versus Nuclear

- 0	5	10	15	20	25
- Local Slope in Degrees

**Solar at Adequate Power**

**Solar at Marginal Power**

**RPS: All of the Planet, All of the Time**

- Terrain Complexity

## Why Use Nuclear Systems in Space?

**•****	****Long-duration operations (> 1 week)**
**•****	****High sustained power (> 10-100 kWe)**

**Distances where solar power density is too low  (> ~1.5 AU)**
**Locations where solar power not readily or continuously available (lunar polar craters, high Martian latitudes)**

## Radioisotope Power Development

- Radioisotope power systems have been used by NASA for the past 30 years
- Radioisotope Power Development efforts focus on increasing the efficiency of future power conversion technologies.
- Lower launch mass and plutonium usage
- First use of new radioisotope power system is being considered for the Mars 2009 Smart Lander.
- Increases the Lander’s lifetime from 180 days (using solar panels) to greater than 1,000 days
- Operates day/night and in all weather and latitudes

**Notes:**
Chris made changes to RTG chart on 4/5/02.
Change made was that he added the first bullet
To the chart.

## NASA Missions That Have Used RTGs

- NIMBUS	B-1	1968 (Aborted)	--	--	--
- 	III	1969	SNAP 19 (1)	~28	PbTe
- APOLLO	11	1969	Heater Units	--	--
- 	12	1969	SNAP 27 (1)	~73	PbTe
- 	13	1970 (Aborted)	--	--	--
- 	14	1971	SNAP 27 (1)	~73	PbTe
- 	15	1971	
- 	16	1972	 
- 	17	1972	 
- PIONEER	10	1972	SNAP 19 (4)	~40	PbTe/TAGS
- 	11	1973	 
- VIKING	  1	1975	SNAP 19 (2)	~35	PbTe/TAGS
-           	  2	1975	 
- VOYAGER	  1	1977	MHW (3)	~150	SiGe
-                      2	1977	 
- GALILEO		1989	GPHS-RTG (2)	~285	SiGe
- ULYSSES		1990	GPHS-RTG (2)	~285	SiGe
- PATHFINDER	1996	Heater Units	 --	--
- CASSINI		1997	GPHS-RTG (3)	~285	SiGe

**	****	****	**** ****Power Level ****	****Thermoelectrics**
_**Missions**__**	**__**Launch Year**__**	**__**Type of RTG**__**	**__**Per Unit (We)**__**	**__**Used**_

## Nuclear Fission Electric Propulsion Research

- Enables new classes of solar system exploration missions with multiple targets
- Eliminates or reduces launch windows requiredfor gravity assists
- Reduces cruise time to distant targets
- Reduces mission cost because smaller launch vehicles may be used

- Technology System
- Flight Validation

- Subsystem Technologies

- DS-1  Technology validation mission

## Nuclear Fission Power Research

- Provides electrical power for the electric propulsion system
- Greater operational lifetime increases the productivity of spacecraft and instruments
- Enables multiple destinations on a single mission
- Provides energy for high-power planetary survey instruments for remote sensing and deep atmosphere probes
- Allows higher bandwidth communications

## Nuclear Fission Power Research

- Provides 10’s KW electrical power for electric propulsion and operation of science instruments
- Significantly more power than ~0.1 KW electrical from radioisotope power systems
- One U.S. nuclear fission power system was launched in mid-1960’s
- Research was conducted through the early 1990’s (SP-100)
- Range of technical approaches available for reactor and power conversion to electricity.  Require  research of multiple approaches before down-selection to optimal design(s).
- Perform parallel in-house and industry/academia/government studies (2-year effort)
- Need to survey and assess industrial base to identify potential suppliers and development needs
- Special materials needed for space-based nuclear fission system
- Need to develop sufficient technical and industrial base (~3 year effort) to support an informed decision for development competition in 2006 timeframe

## NEP System Overview and Technology Options

- Ion Engine
- MPD
- Hall
- VASIMR
- Pulsed Inductive Thruster

- Options:
- Brayton - moderate/high power
- Thermionic Power Conversion
- Stirling - low/moderate power
- Thermoelectrics
- Rankine - Liquid Metal

- Reactor Cooling Options:
- Heat Pipe Cooled
- Direct Gas cooled
- Liquid Metal Cooled

**NEP System Overview and Technology Options**

- Propellant

- Radiator

*Waste Heat *

*(Low T)*

*Electric *

*Power*

*Heat *

*(High T)*

- Thruster(s)

- Power

- Converter

- Experiments &

- Spacecraft

- Subsystems

**Power Subsystem**

- Fission

- Energy

- Source /
- Shield

- Spacecraft

- Subsystems

*Heat*

- Power Conversion converts heat
- to electricity.

- Nuclear Reactor (core)  produces thermal energy via fission of U-235.  Fission reaction rate (power) actively and passively controlled by neutron balance (produced vs lost).  Reactor cooling system transports heat to power converter and maintains stable core temperature.

- Thruster uses electrical energy to produce thrust.  Energy accelerates propellants achieving high exit velocities (Isp)

- Power Processing Unit and Power Management and Distribution (PPU / PMAD) dependent on power conversion and thruster subsystem choices.  High Isp ion thrusters need high voltage (>4000 V).

- PPU /
- PMAD

## NEP System Challenges

***Developing NEP systems for space flight represents a unique systems engineering and integration challenge***

**Environments are extreme**
- Thermal subsystem design a challenge with large deployable radiators, nuclear subsystem, power conversion, and bus/payload thermal requirements
- Radiation environment compounded by presence of neutrons and gammas from reactor – dependent on vehicle configuration (boom) and shield mass. Demands stringent EEE parts requirements (SEE and total dose).
- These challenges exacerbated by long required lifetimes
**Nuclear Safety**
- Driven by requirement for reactor to remain subcritical during all credible pre-launch and launch accidents/failures
**Test and Verification Approach**
- Maximize use of non-nuclear testing to reduce costs
- Provide confidence in meeting lifetime requirements either through accelerated tests or performance degradation/extrapolation
**Subsystem Impacts to Overall Vehicle Configuration**
- Radiator location, orientation and view factors
- Boom length versus shield mass
- Thruster location to direct thrust through cg, while keeping cg migration to minimum
- Plume impingement
**Need for Deployable Mechanisms**
- Lightweight deployable radiators
- Boom
**System-level Drivers on Power Conversion Subsystem**
- May force consideration of passive or other dynamic methods

## NEP System Challenges

***NEP systems require demanding performance***

**Specific impulse (Isp) in the range of 6000 to 9000 sec**
- Isp  Exhaust momentum per unit mass of propellant (i.e., exhaust velocity)
- Isp is time that thruster can deliver 1 lbf of thrust with 1 lbm of propellant – quantifies how well propulsion system utilizes propellant
**Alpha (********jet****) less than or equal to 50 kg/kW****jet**
- jet = mass of system/jet power of thruster exhaust (not input power to thrusters)
- System mass includes dry mass of reactor, shield, radiator, power conversion, thrusters/PPU, and PMAD
- Payload mass includes boom, spacecraft bus and subsystems, payload, and dry mass of propellant tanks
-  electric = thruster efficiency • jet
**Propellant throughputs of 2000 to 4000 kg, depending on mission and destination**
**Operational lifetimes of 10 to 20 years, depending on mission and destination**

## OSS Selection Process

- Requirements established by Space Science Strategic Plan and vetted by the National Academy of Sciences
- Technology research is openly competed, and is open to U.S. industry, universities, NASA Centers, FFRDCs, and other government agencies
- NASA HQ leads peer review and selection process
- The Office of Space Science competes 82% of its program

## Nuclear Systems Initiative Management Review 

**Chair:****	****Christopher Scolese, Deputy Associate Administrator**
**	****for Space Science, NASA HQ**
**Vice-Chair:****	****Colleen Hartman, Solar System Exploration Division Director, NASA HQ Plaetary Science Representative**
**Members:****	****Earl Wahlquist, Associate Director for Space and Defense Power Systems, Office of Nuclear Energy, Science and Technology, Department of Energy**
**	****Gerald Barna, Deputy Director, NASA GRC **
**	****James Garvin, Mars Program Scientist, NASA HQ**
**	****Eugene Tattini, Deputy Director, NASA JPL**
**	****Wallace Sawyer, Associate Director, NASA KSC**
**	****Robert Sackheim, Associate Director, NASA MSFC**
**	****	**

**Invited Representatives from the following NASA HQ Offices:  Space Flight, Aerospace Technology, Safety and Mission Assurance, International Relations, Biological and Physical Research,  Legislative Affairs and Public Affairs.**

## Summary

- Radioisotope power systems enable surface missions
- Outer planetary exploration missions are enabled by NEP.
- Continue the 30-year relationship with DOE in providing radioisotope systems for space exploration.
- Space exploration, coupled with nuclear systems, has the potential for exciting a new generation of scientists and engineers in the nuclear field.

*Development of RPS and NEP will revolutionize our ability to study the Solar System’s natural laboratories.*

*Mars Surface*

*Galilean Satellites*

*Titan*