HighEnergy, OuterPlanetary Missions of Interest

1
High-Energy, Outer-Planetary Missions of Interest

• Ralph L. McNutt, Jr.
• Johns Hopkins University Applied Physics
  Laboratory
• Nuclear and Emerging Technologies for Space -
  2009
• Special Session Nuclear Thermal Propulsion
  Systems
• Atlanta, Georgia
• 16 June 2009

2
Planetary Science is the Discovery and
Exploration of Our Neighborhood in Space
The Ultimate Goals Lead To the Edge of the Solar
System and Beyond
Graphic from the Interstellar Probe Science and
Technology Definition Team NASA/JPL
3
For Any Mission There Are Four Key Elements

• National Policy/Science the case to go
• Technology the means to go
• Strategy the agreement to go
• Programmatics the funds to go
• A well-thought-out approach with all key elements
  is required to promote and accomplish a
  successful exploration plan

4
The Case to Go Science/Politics

• The Vision for Space Exploration
• NRC Decadal Study
• While this report maps out a strategy for the
  2003-2013 time frame, final definitive answers to
  many of the questions will again be decades long,
  employing and requiring more and more advanced
  approaches, techniques, and technologies.
• And a new survey is starting up for the following
  decade

5
The Vision for Space Exploration- President G.
W. Bush, 14 January 2004

• Implement a sustained and affordable human and
  robotic program to explore the solar system and
  beyond
• Extend human presence across the solar system,
  starting with a human return to the Moon by the
  year 2020, in preparation for human exploration
  of Mars and other destinations
• Develop the innovative technologies, knowledge,
  and infrastructures both to explore and to
  support decisions about the destinations for
  human exploration and,
• Promote international and commercial
  participation in exploration to further U.S.
  scientific, security, and economic interests.

6
Rationales Have Not Changed

• The first principal objective is the scientific
  exploration of space, the planets, and later, the
  stars.
• This is an effort to learn the basic physics,
  chemistry, medicine, or biology of these new
  places.
• It includes the invention, research, and
  development of new instruments and scientific
  devices.
• A secondary objective is, of course, to apply
  the discoveries made in space exploration in the
  basic sciences to other important applications,
  devices, and pieces of equipment, thus making it
  possible that life on the earth will be more
  comfortable, more pleasant, or more useful
  because of these discoveries which are yet to
  come.
• G. P. Sutton - 1.391 of Trends in
  Astronautical Developments in Handbook of
  Astronautical Engineering, ed. H. H. Koelle, 1961.

7
The Targets Four Categories

• Primitive Bodies
• Occur throughout the solar system
• Thousands in number
• Inner Solar System
• Venus and Mercury
• Thermal (both) and other extreme (Venus)
  challenges
• Mars - easiest planet for a sample return - but
  STILL DIFFICULT
• Giant Planets and Large Satellites
• Span the distance from 5 AU (Jupiter) to 30 AU
  (Neptune)

8
Primitive Bodies Lie at the Edge of theNew
Solar System

• Trans-Neptunian objects (TNOs) are primitive
  bodies
• Pluto and Eris currently classified as dwarf
  planets
• Sedna is most distant out to 975 AU and period
  12,000 years

Discovery of Sedna 14 Nov 2003
9
Answering Solar System Science Questions is a
System of Systems Problem
10
How well have past plans worked?How should we
plan for the future?
Worldwide successful launches 1957-1998
3973 Successful lunar and planetary missions 112

• Those who cannot remember the past are condemned
  to repeat it.
• G. Santayana (recalled on the philosophers
  death, 1952)

11
The Means to Go Technology

• To scope, must set requirements
• Outer TNOs reach to 1000 AU (Sedna)
• Uncharted Oort Cloud to 1 light year (64,000
  AU)
• Robotic missions trade transit time against
  autonomy, mission operations costs, and technical
  complexity
• Cryogenic , landed rovers present extreme
  engineering challenges of their own - solutions
  require mass
• Autonomous operations are imposed by long (hour)
  round-trip light times
• Holy grail of outer-solar-system science is
  return of intact, cryogenically-preserved samples
  for analysis only doable in Earth (or near-Earth)
  lab
• Human missions have limits robotic missions do
  not have
• Radiation exposure
• Low-gravity
• Expendables (potable water, oxygen, food)
• Isolation - 2 x spice island voyages with lt 1/20
  the crew
• 2 years out 1 year exploration 2 years back
• Exceed only analogues to date ISS and South Pole
  Station, Antarctica

12
The Means to Go Technology
Propulsion is key!
13
Propulsion Issues for Robotic Missions
Triton geysers (Voyager 2 at Neptune)

• Going to the outer solar system and into orbit
• Landing on any solid planet (Mercury through
  Pluto minor bodies) - high thrust required

• Sample returns to Earth - high thrust required

14
Difficult Robotic Missions
15
Solar System Polar Regions

• Ganymede 60N
• Mars 75N
• Enceladus 60N
• Miranda and Enceladus same size

16
Enceladus
EAGLEEnceladus Astrobiology Geophysical
Lander Expedition

• Small moon about the size of Arizona
• Highly reflective, covered in nearly pure water
  ice
• Many types of terrain
• Smooth surfaces lt100 million years old
• Older cratered surfaces
• Fissures indicate tectonic activity
• Magnetic field distortions
• Atmosphere over south pole coming from a geyser
• H2O, CO2, N2, CH4, and possibly light organics
• Hot spots on south pole over tiger stripe
  surface cracks.

NASA Academy GSFC Group Project 2006
17
Example EAGLES Propulsion System Overview

• Cassini Heritage
• Monomethylhydrazine/
• Nitrotetroxide (MMH/NTO) Fuel system
• Specific Impulse 340s
• Deployable Fuel Stage

Mission est. cost 1.1 B
18
Interstellar Space Our Local Backyard
The Voyagers - data still coming back on their
way to the stars
Launched in Aug and Sep 1977, both Voyagers have
now crossed into the heliosheath
19
The Next Step Planning for an Interstellar Probe
20
Assembling the Pieces

• Figure is to approximate scale
• Earth Departure Stage is only partially fueled to
  optimize launch energy
• First iteration C3270 km2/s2
• Corresponding asymptotic speed from the solar
  system is 19.0 km/s 4 AU/yr
• New Horizons
• Launched to 164 km2/s2
• Pluto flyby at 13.8 km/s 2.9 AU/yr
• Voyager 1 current speed 3.6 AU/yr
• Voyager 2 current speed 3.3 AU/yr
• To reach 9.5 AU/yr (45 km/s) with only a launch
  from Earth would require C3 1,016 km2/s2
• Even with an Ares V, launch remains only one
  component

Earth orbital speed 29.79 km/s 1 AU/yr 4.74
km/s
21
Nuclear Upper Stage (?)

• Nuclear stage advantages
• More performance than Centaur V1
• Lower mass
• Earth escape trajectory
• Nuclear stage disadvantages
• More expensive than Centaur
• Larger (low LH2 volume)
• Not solar system escape trajectory
• Requires development
• Gamma engine thrust 81 kN (18,209 lbf)
• BNTR engine thrust 66.7 kN (15,000 lbf)
• 3 BNTRs baselined for Mars DRM 4.0 of 1999
• Nuclear EDS not acceptable
• Not Earth-escape trajectory
• Comparable thrust engine to NERVA 2
• 867.4 kN (195 klbf)
• Stage mass 178,321 kg wet, 34,019 kg dry
• Compare S IVB 119,900 kg wet, 13,300 kg dry
  J-2 486.2 kN (109.3 lbf)
• No development plans or identified requirements

15 klbf BNTR engine
22
Comparing the Options Speed to 200 AU and Beyond

• Probe speed versus heliocentric distance
• To 200 AU
• Log distance
• JGA is the discontinuity

Ares V with nuclear upper stage and REP gives
best performance
23
Comparing the Options Time to 200 AU

• Spread among years to 200 AU
• Widens in going to even larger distances
• Initial goal had been 15 years to 200 A
• Options here are 22 to 38 years
• Ares V speeds up arrival to 1000 AU by 31 years

24
The Agreement to Go Strategy

• Recommended ground rules and/or criteria
• ? Size of launch vehicles to be developed should
  be compatible with the highest payload
  requirements, e.g. sample return.
• ? Mission and program concept should keep human
  extra-vehicular activities to a minimum Do on
  Earth what you can do on Earth!
• ? Launch costs are not a valid measure for
  comparison, rather the total cost to the point of
  destination, including operations in space,
  unloading and assembly of space facilities must
  be included.
• ? Make use of available and proven subsystems,
  e.g. do not develop new engines for each flight
• The main problem is not the lack of appropriate
  technology or financial resources, but the lack
  of a program deemed socially and politically
  desirable !
• NOVA AND BEYOND A Review of Heavy Lift Launch
  Vehicle Concepts in the POST-SATURN Class
• H.H.Koelle (2001)

25
The Robotic Probe Vision(or Do we need
Astronauts?)
Apollo 17

• Launch a probe to a target
• Probe returns knowledge - not data
• BUT without return of all data, how is the
  knowledge to be validated?
• Return of all data requires large bandwidth
• Drives receiver and transmitter sizes and
  transmitter power
• Compression leaves doubts of data fidelity

Luna 24
Data return drives power and, hence, mass Mass
drives propulsion Did we REALLY think EVERYTHING
through ahead of time, though?
26
Is Human Flight Beyond Mars Doableor Desirable?
An artists drawing of a human exploration base
on Callisto, Jupiters second largest moon. -
from The Vision for Space Exploration, February
2004
27
South Pole Station 1956
Credit U.S. Navy, National Science Foundation

• We were like men who had been fired off in
  rockets to take up life on another planet. We
  were in a lifeless, and almost featureless world.
  We were now face to face with raw nature so
  grim and stark, that our lives could be snuffed
  out in a matter of minutes.
• Paul Siple in 'Living at the Pole'

28
A Timetable for the Solar System
Solar system family portrait taken by Voyager 1

• Robotic missions are the pathfinders - this will
  not change!
• Initial tests with ARGOSY-R for sample returns
• Scale the architecture in size and power to reach
  increasing distance at roughly constant travel
  time

29
2-Yr Outbound Trajectories

• As the heliocentric distances increase, so do the
  flyout speeds, linearity of the trajectories, and
  power-plant mass/power requirements

30
The Funds to Go Programmatics
The VSE and beyond
We are here
The outer rings of Saturn and the Earth from the
Cassini spacecraft Will a human crew ever see
this from the Saturn system?
A vision from 1954
Enceladus is here
31
U.S. GDP Exhibits Exponential Growth
Acceptable Costs for Exploration

• Gross Domestic Product of the U.S. shows an
  e-folding time of 28 years
• NASA budget has been sporadic in its tracking

32
Radioisotope electric propulsion spacecraft en
route to the heliopause 150 AU away
In the meantime, we must keep doing science and
moving out
The greatest gain from space travel consists in
the extension of our knowledge. In a hundred
years this newly won knowledge will pay huge and
unexpected dividends. Wernher von Braun
33
Determination Worked for New Horizons
34
Get out your pencils!