DOW-UAP-D143, AAWSAP DIRD, Laser Lightcraft Nanosatellites, November 2010

This document is a Defense Intelligence Reference Document (DIRD), a technical reference format used by the Defense Intelligence Agency (DIA) to capture baseline knowledge on a specific topic for later analytic use. DIRDs are best understood as reference and synthesis products rather than as original research. It is one of 38 DIRDs produced under the Advanced Aerospace Weapon System Applications Program (AAWSAP) between 2009 and 2011. Because AAWSAP’s scope permitted a broad range of supporting topics, not every DIRD in the series directly concerns aerospace systems or future threat assessment. The following summary reflects the DIRD’s scope and framing at the time of writing and should not be read as implying current validation of the concepts discussed. This DIRD examines laser-propelled “Lightcraft” as a possible low-cost method to launch very small satellites into low Earth orbit by using a remote high-energy laser to supply most of the propulsion energy rather than relying entirely on onboard energy sources. The report combines a survey of nanosatellite trends with a review of “Lightcraft” propulsion concepts, vehicle design, beam-control requirements, and mission studies, and argues that the most promising application is the launch of nano- or pico-satellites, especially Earth- and space-observing payloads of a few kilograms or less. It presents the concept as potentially much cheaper than conventional multistage rockets for very small payloads, while also noting significant practical constraints including strict beam-riding geometry, atmospheric losses, demanding pointing and adaptive-optics requirements, and heavy dependence on large ground-, sea-, or air-based laser infrastructure. Overall, the document presents laser “Lightcraft” as a technically plausible launch concept whose attractiveness depends on whether the supporting laser and beam-control system can be made reliable and economical at operational scale.

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Defense
Intelligence
Reference
Document
Defense Futures
01 November 2010
ICOD 30 August 2010
DIA-08-1011-001
Laser Lightcraft
Nanosatellites
Laser Lightcraft Nanosatellites
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The Defense Intelligence Reference Document provides non-substantive but
authoritative reference information related to intelligence topics or methodologies.
Prepared by:
Technology Warning Division (DW0-4)
Defense Warning Office
Directorate for Analysis
Defense Intelligence Agency
611thnr·
AAP Person 58
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authorized.
This product is one in a series of advanced technology reports produced in FY 2010 under the Defense
Intelligence Agency, Defense Warning Office's Advanced Aerospace Weapon System Applications.---....
(AAWSA) Program. Comments or questions pertaining to this document should be addressed to I -·--. ) MP Person
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Contents
Chapter 1: Nanosatellite Technologies .................................................................. 3
Chapter 2: Laser Lightcraft Nanosatellite Propulsion ..............................................11
Chapter 3: Laser Lightcraft Weapon Mission Selection Study ..................................27
Chapter 4: Summary of Multi-Megawatt Laser Study for Lightcraft Propulsion
Applications .....................................................................................................42
Chapter 5: Conclusion ......................................................................................68
References.......................................................................................................71
Figures
Figure 1. Air Force X-25LR Laser Lightcraft ..........................................................12
Figure 2. AFRL Test Vehicle in Vertical Flight ........................................................14
Figure 3. Time-Lapse Photo of a Lightcraft Undergoing an Outdoor Vertical Flight Test 15
Figure 4. Lightcraft Flight-Test Vehicle Used in Horizontal Guide-Wire Flight Tests ......16
Figure 5. Lightcraft Undergoing Horizontal Guide-Wire Flight Test ...........................16
Figure 6. Lightcraft Undergoing Horizontal Guide-Wire Flight Test ...........................17
Figure 7. Lightcraft Concept ...............................................................................18
Figure 8. Lightcraft Trajectory and Associated Pointing Angles .................................19
Figure 9. Lightcraft Vehicle Evolution ...................................................................20
Figure 10. Attenuation Effects on Captured Laser Beam Power................................22
Figure 11. Influence of Trajectory and Laser Wavelength on Captured Power.............22
Figure 12. Captured Laser Power vs. Increasing Range from 11.2 µm CO2 Laser ........23
Figure 13. Influence of Lightcraft Range and Pointing Angles on Captured Power........24
Figure 14. Ground/Sea-to-Space Concept .............................................................27
Figure 15. Air-to-Space Concept . ........................................................................28
Figure 16. Schematic of Power Oscillator Optics ....................................................44
Figure 17. Schematic of MOPA ............................................................................45
Figure 18. Schematic of the Laser N2/CO2/H2 Gas Flow System ................................45
Figure 19. Northrop Grumman's Joint High Power Bulk Slab Solid-State Laser ...........48
Figure 20. DARPA's High Energy Liquid Laser Area Defense System .........................50
Figure 21. Phase Change Materials Allow Storage of Large Intermittent Heat Loads
While Slow Regeneration Removes Heat from Aircraft ............................................52
Figure 22. Typical HPFL MOPA Design..................................................................54
Figure 23. Fiber Laser Beam Combining Techniques ...............................................54
Figure 24. Pumping Fiber Lasers .........................................................................56
Figure 25. Large and Small Diameter Fiber Lasers .................................................56
Figure 26. Single Mode Fiber Laser Modules ..........................................................57
Figure 27. Multimode HPFLs ...............................................................................57
Figure 28. Free-Electron Laser............................................................................58
Figure 29. Free-Electron Laser Mechanism ............................................................58
Figure 30. Free-Electron Laser Electron Beam Phase-Space Evolution .......................59
Figure 31. Recirculating-Beam FEL System ...........................................................60
Figure 32. High-Power FEL Optical Resonator ........................................................62
Figure 33. Notional Long Range HEL Beam Control System.....................................64
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Figure 34. HEL Beam Pointer/Tracker...................................................................65
Figure 35. Basic Shared Aperture Beam Control System .........................................66
Figure 36. HEL Adaptive Optics System................................................................67
Tables
Table 1. Laser Lightcraft Model Cost Summary ......................................................25
Table 2. Performance and Estimated Weights for a Hybrid Rocket and Lightcraft ........30
Table 3. Estimated Costs for Hybrid Rocket and Lightcraft Launch Vehicles for ETO
Flight..............................................................................................................32
Table 4. Influence of Target Velocity and Intercept Angle on Impact Energy and
Required Mass ..................................................................................................33
Table 5. Influence of Lightcraft and Target Velocity on Impact Energy and Required
Mass ...............................................................................................................35
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Laser Lightcraft Nanosatellites
Summary
Miniaturized satellites are spacecraft of unusually low mass and small size, usually
under 500 kg in total mass. The term "minisatellite" refers to a spacecraft with a wet
mass (including onboard propellant) of 100 kg to 500 kg. Microsatellite or "microsat" is
a spacecraft with a wet mass of 10 kg to 100 kg. Nanosatellite or "nanosat" is a
spacecraft with a wet mass below 10 kg. Picosatellite or "picosat" is a spacecraft with a
wet mass of 0.1 kg to 1.0 kg. Picosats are also called sub-nanosats.
The primary reason for miniaturizing satellites is to reduce cost. Heavier satellites
require larger launch vehicles of greater cost while smaller, lighter satellites require
smaller and cheaper launch vehicles and can sometimes be launched in multiples or
"piggyback" using excess capacity on larger launch vehicles. Miniaturized satellites
allow for cheaper designs as well as ease of mass production. However, few satellites
of any size other than communications constellations, where dozens of satellites are
used to cover the globe, have been mass produced in practice.
Besides the cost issue, the main rationale for the use of miniaturized satellites is the
opportunity to enable missions that a larger satellite cannot accomplish, such as:
• Constellations for low data rate communications.
• Using formations to gather data from multiple points.
• In-orbit inspection of larger satellites.
Many of these missions require numerous small spacecraft in a constellation or
"swarm." These include orbital communications networks and swarms of small
satellites to conduct remote sensing, and to provide unique perspectives on
astronomical bodies of interest. For instance, 100 or more nanosats could be deployed
from a mother ship to their final destination in space for deployment.
Provisions for orbital maneuvers as well as attitude control, multiple sensors, and
instruments, and full autonomy will yield a highly capable miniaturized satellite. All
onboard electronics will survive a total radiation dose rate of several hundred kilorads
over a several year mission lifetime (at least 100 kilorads over two years). Nanosats
developed for in-situ measurements will be spin-stabilized, and carry a complement of
particles and fields instruments. Nanosats developed for remote sensing measurements
(MASINT) or surveillance and eavesdropping (SIGINT) will be three-axis stabilized, and
carry a complement of imaging and radio wave instruments. Autonomy both onboard
the nanosats and at the ground stations will minimize the mission operational costs for
tracking and managing a constellation.
To reduce overall mission cost, advanced technology components and a novel laser
propulsion system will be used to make nanosats and their onboard instruments
compact, lightweight, low power, low cost, and able to survive their radiation
environment over a several year lifetime. Each nanosat will be manufactured and
tested for a recurring cost not to exceed $500k. By producing a large quantity of
nanosats for a given mission, the per-unit cost will be reduced to a small fraction of
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satellite procurements for traditional missions. Mission operation costs will be
minimized by the incorporation of both onboard and ground autonomy and use of
heuristic systems.
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Chapter 1: Nanosatellite Technologies
OVERVIEW
Nanosats require technologies that radically reduce the mass and power of components
without compromising performance. In addition to miniaturizing components, methods
to integrate similar functions across subsystems are being evaluated. For example, all
subsystem electronics, including instruments, could be integrated within the Command
and Data Handling (C&DH) subsystem. Multifunctional solutions also offer significant
savings over traditional approaches. Technology investments are required to develop
or adapt components to accommodate the expected radiation environment. Simple,
effective methods of thermal control are essential to keep the nanosat operational
during extreme temperature variations. Autonomy is a critical technology that impacts
every subsystem. Constellations with tens to thousands of nanosats must be highly
autonomous to be practical. The nanosat ground system must be kept inexpensive,
simple, and made inter-operable with other missions.
PROPULSION
In the baseline mission, nanosat propulsion is needed for two distinct functions: 1) each
nanosat must raise its orbit apogee to the appropriate radius, 2) and it must reorient
the axis of the spinning nanosat from the velocity direction (within the orbit plane) to
its science mission attitude (perpendicular to the ecliptic plane). These maneuvers
present challenging velocity change (1W) and attitude-control (ACS) requirements.
Requirements for the Av Thruster:
• Total impulse: 3,000 to 7,000 N-sec.
• Thrust: 445 N maximum.
• Input power (during burn): < 1 watt.
• Specific impulse: 280 seconds.
Requirements for the ACS Thruster:
• Total impulse: $ 2.4 N-sec.
• Minimum impulse bit: 0.044 N-sec.
• Response time: < 0.005 sec.
• Pulse rate: 1 Hz.
It turns out that the tiv and ACS thrusters can have independent systems. We propose
a new innovation whereby the nanosat launch vehicle propulsion system also serves
double duty as the tiv thruster system, and this can be done without having to carry the
propulsion energy source into orbit. This can only be achieved via laser propulsion in
which the laser beam energy that is used to launch a nanosat into orbit is also used to
provide tiv thrust in orbit. This novel innovation dramatically reduces the mass, size,
cost, and complexity of nanosats because they will only need to carry minimal onboard
ACS thrusters and propellant to carry out routine, minor attitude adjustments. The
innovative nanosat laser propulsion concept is presented in Chapter 2.
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Miniaturized solid propellant gas generators could be used as ACS thrusters. Forty­
eight 50 mN-sec pulses are required to reorient the nanosat after it achieves the
required orbital altitude. Although this could be achieved either by a monopropellant or
a cold gas thruster, it could also be achieved using an array of gas generators. Such
miniaturized gas generators have already been successfully built and commercialized by
companies such as MOOG and Lockheed-Martin Space Systems. By incorporating
micro-electromechanical systems (MEMS) techniques, the devices have been produced
relatively inexpensively. Miniaturized electric propulsion ACS thrusters, such as pulsed
plasma and MEMS field-emission electric propulsion (MEMS FEEP) thrusters, have been
developed and are now emerging into widespread commercialization.
GUIDANCE, NAVIGATION AND CONTROL
Guidance Navigation and Control (GN&C) subsystem key technologies and concepts
have been identified to enable successful altitude determination of spin-stabilized and
three-axis-stabilized nanosats for future missions. They include miniaturization of a
sun sensor and horizon crossing indicator. The miniature precision "fan" sun sensor will
pinpoint the sun virtually everywhere in the entire celestial sphere with every satellite
rotation. The sun sensor will be required to weigh less than 0.25 kg, draw less than 0.1
watt, operate on no greater than a 3.3 volt bus, and meet a 0.1° resolution
requirement. The miniature horizon crossing indicator has a small bore-sight field of
view that is mounted at an angle off the spin axis. As the spacecraft rotates, a cone of
coverage is formed. The sensor must be capable of detecting Earth over a range of
orbital radii with a pointing accuracy of 0.05°. Total horizon crossing indicator weight
and power will be less than 0.2 kg and 0.1 watt, respectively.
Of particular interest to Constellation missions is the incorporation of GPS onboard the
nanosats, to eliminate ground-based ephemeris generation. This allows for increased
autonomy and simpler, more accurate time resolution onboard the spacecraft. For GPS
to fit within the constraints of a nanosat, the receiver electronics need to be
miniaturized into a layer within the