A NANOSATELLITE MISSION TO ASSESS SOLAR SAIL PERFORMANCE IN LEO Kieran A. Carroll, Gedex Inc. Henry Spencer, SP Systems Robert E. Zee, Space Flight Laboratory

A NANOSATELLITE MISSION TO ASSESS SOLAR SAIL PERFORMANCE IN LEO

Kieran A. Carroll, Gedex Inc.

Henry Spencer, SP Systems

Robert E. Zee, Space Flight Laboratory

George Vukovich, Canadian Space Agency

20-22 July 2010 A Nanosatellite Mission to Asses Solar Sailing Performance in LEOInternational Solar Sail Symposium 2010, New York

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Goals of This Presentation

• To introduce publicly the CanX-9 solar sail technology mission

• To convey a sense of the design approach that has been followed.

• To provide a starting point for coordinating this mission’s objectives with those of others who are working to mature solar sailing technology, e.g.:– IKAROS– Nanosail-D2– Lightsail-1– Cubesail


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Background: History of Solar Sailing in Canada

• 1978: Modi & Van Der Ha orbital dynamics papers (UBC)


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• 1978: Modi & Van Der Ha papers• 1988-92: Canadian Solar Sail Project (CSSP)

– CCQJC Race to Mars– Canadian Space Society– University of Toronto Institute for Aerospace Studies

(UTIAS)– (Team members included Carroll and Spencer)


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CSSP Initial Design Concept

• Novel non-spinner• Hexagonal planform• “Venetian blind” sail vanes:

– Stowed rolled-up– Deployed and actuated by

cables• Compressive booms, each

60 m long• 500 kg, 10,000 m2

• Smallsat-class • Ariane 4 launch to escape


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CSSP Eventual Preliminary Design• Novel spinner• “Pinwheel” configuration• 30 vanes, each 30 x 0.5 m,

stowed and deployed roller-blind fashion

• 3 of the vanes with adjustable angle of attack for spin-rate control

• Precess spin vector (and hence sail pointing) direction via shifting mass center

• 25 kg, 500 m2

• Microsat-class• Scout or Pegasus launch to

escape


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• 1978: Modi & Van Der Ha papers• 1988-92: Canadian Solar Sail Project (CSSP)

– CCQJC Race to Mars– Canadian Space Society– University of Toronto Institute for Aerospace Studies

(UTIAS)– Team members included Carroll and Spencer


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• 1978: Modi & Van Der Ha papers• 1988-92: CSSP• 1990s: KAC @ Dynacon

– Polar Relay Satellite (POLARES) concept study:• ~100 kg polesitter for north pole region data backhaul• With SPAR, for Canadian DND• Heliogyro-like, with ~25 kg despun comms payload• (Independently conceived pole-sitter concept)

– Several solar sailing conference papers– Solar sail applications study for CSA– Supervised M.A.Sc. magnetosphere mission study


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• 1978: Modi & Van Der Ha papers• 1988-92: CSSP• 1990s: KAC Dynacon solar sail activities• 1996-2003: MOST microsat mission for CSA

– Learned how to design and build microsats– UTIAS Space Flight Laboratory founded, major

subcontractor to Dynacon


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• 1978: Modi & Van Der Ha papers• 1988-92: CSSP• 1990s: KAC Dynacon solar sail activities• 1996-2003: MOST microsat mission• 2000-2010:

– SFL nanosats– CanX program


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SFL’s CanX Program

• Canadian Advanced Nanospace eXperiment program

• Developing/flying significantly capable nanosats (1-10+ kg)

• Providing nanosat launch services via XPOD launcher i/f

• Current missions use the Generic Nanosat Bus (GNB) platform (20x20x20 cm)


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CanX-9 Mission Concept

• Fly a solar sail technology demonstrator using SFL nanosat technology

• Seek a partner to provide the solar sail subsystem• Demonstrate directed solar sail thrusting• Fly as a secondary payload in LEO• Expected total cost: <<$10M


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CanX-9 Programmatics• Initial preliminary design carried out at SFL• Partners include:

– Technology P.I. and Team• Source of mission requirements• Processes technology payload data to accomplish tech demo• Membership drawn from participating organizations

– SFL• Mission prime contractor• Bus and XPOD supplier• Arrange launch

– L’Garde• Provision of solar sail subsystem

– CSA• Supported initial design study• Considering funding the mission


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Mission Objectives

• Address issues impeding the use of solar sailing in operational missions

• Qualitative:– Demonstrate significant orbit changes via active solar sailing– Flight-test inflatable-boom square-sail technology

• Quantitative:– Determine sail reflectivity to within 1% by measuring orbit

changes– Determine changes in SRP force and torque with time


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Some Design Drivers/Issues• Cost drives use of nanosat

development approach:– Thus COTS EEE parts used– Radiation TID constraint drives

altitude limit to below 1000 km or above GEO

• Cost drives use of secondary-payload launch:– Secondary launch availability

constrains orbit availability and launch timing

– Sun-synchronous orbit preferred due to availability of launches, and resulting slowly-varying Sun-phase angle which simplifies some aspects of mission and system design

• Lack of available SRP torque actuators drives preference for low Earth orbit, thus 1000 km upper altitude constraint:– Strong Earth magnetic field in LEO

advantageous– Also reduces power for comms

• Atmospheric force/torque effects provide a 700 km (TBC) lower altitude constraint:– Issue: magnitude of these forces

and torques difficult to analyze in advance (“area of active research”)

– Will depend somewhat unpredictably on launch timing and Solar cycle phasing


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Mission and System Design

• Secondary payload launch using XPOD• Sun-synchronous orbit, 700-1000 km altitude• Sail area 25 m2 , mass <14 kg, mass/area ratio: <560

grams/m2 • Payloads for measuring orbit changes to determine

reflectivity to within 1% in 1 month• Use SFL UHF-up/S-band-down ground station• Quick-look payload data evaluation capability to support

day-to-day mission planning• Non-real-time analysis of payload data to accurately

estimate model parameters for solar radiation pressure and atmospheric forces


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XPOD Duo Launcher I/F• Developed for CanX-4/5 mission• Capacity:

– Designed to carry a dual-GNB bus– 20x20x40 cm– 14 kg

• Size (w/o spacecraft):– 47 x 47 x 52 cm– 10 kg

• Customizable• Relatively softer ride• Can accommodate fixed appendages


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Payloads• Solar sail subsystem

– Inflatable-boom square sail– To be provided by L’Garde

• Cameras– To provide deployment video– Boom-mounted to get far enough above sail plane for a good view

• GPS receiver– To provide low-frequency data on orbit changes– Flight heritage from CanX-2

• 3-axis accelerometer– To provide high-frequency data on orbit changes– Performance requirement: 10-7 m/s2 RMS accuracy at 0.01 Hz

• Total mass ~ 3 kg


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Satellite Design

• Bus– Thermal– OBC– Radios– Power– Structure– ACS

• Payloads– Solar Sail subsystem– Cameras + boom– GPS receiver– Accelerometer

Per existing GNB designs

Significantly modified GNB designs

New designs


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CanX-9 Bus

• To be developed by SFL• Mass ~ 12.5 kg

– Including sail support structure– Including 25% margin

• 20x20x40 cm main structure:– 20x20x20 cm lower bus– 20x20x15 cm upper bus– Sail stowed in 20x20x5 cm “sail-

box” layer between lower and upper bus sections


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CanX-9 With Sail Deployed


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Solar Sail Subsystem

• To be supplied by L’Garde• Miniaturized version of L’Garde

20m ground system demonstrator:– Square sail, 5.5m across flats,

25 m2 area– Four 4.1m inflatable booms,

thermally rigidized– Stripe-net support

• Mass ~ 1.5 kg (including 20% margin):– Sail: 0.2 kg– Booms: 0.3 kg– Deployment gear: 1.0 kg


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Attitude Control Subsystem

• Zero-momentum, 3-axis stabilized to 1 degree accuracy• Sensors:

– 9 Sun sensors on bus faces– 3-axis magnetometer on fixed boom– 3 angular rate sensors

• Actuators:– 3 magnetic torque rods– 3 reaction wheels

• All hardware and ACS software has CanX flight heritage• Mass ~ 1.75 kg, power ~ 4W


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Power Subsystem• Power Loads by Mode:

– Safe-Hold: 2 W– Detumble:2.5 W– Pre-deployment: 6 W– Deployment: 29 W– Post-deployment: 9 W

• Sail boom heaters and valves: – 14 W, for 1-2 orbits around

deployment time• Payload power:

– 2-3 W orbit-average• Transmitter power:

– 5 W, 100% duty cycle when sending down deployment video

• Power Supply– 45 pairs of ~ 27% efficiency (BOL) triple-junction solar cells– 27 pairs body-mounted– 18 pairs wing-mounted– Each with 920 mW max power generating capacity at worst-case-hot

temperature– 2x 20 W-hr Li-ion batteries

• Mass:– ~ 2.25 kg


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Thermal Subsystem• Mostly passive (careful choice of coatings)• Spot-heaters on some parts (battery, accelerometer)• Large heaters in sail booms, to raise their temperature prior to

deployment• Boom-to-bus insulation to keep booms from cooling too quickly

during deployment• Choice of boom epoxy, to have a glass transition temperature to

match bus worst-case-hot temperature• Analysis of Solar radiation incident on the bus versus sail orientation

with respect to the Sun:– Maximum reflected-Sunlight bus heating level of ~ 12W (versus direct-

incidence Sunlight ~ 35W)• Analysis of sail heating radiatively coupling into bus heating:

– Face-on to the Sun, the sail temperature can reach 150 C– This effect is largest when the reflected Sunlight effect is least

Documents

A NANOSATELLITE MISSION TO ASSESS SOLAR SAIL PERFORMANCE IN LEO Kieran A. Carroll, Gedex Inc. Henry Spencer, SP Systems Robert E. Zee, Space Flight Laboratory