solar sail
DESCRIPTION
Solar Sail. Department of Aerospace Engineering and Mechanics AEM 4332W – Spacecraft Design Spring 2007. Team Members. Solar Sailing:. Project Overview. Design Strategy. Trade Study Results. Orbit. Eric Blake Daniel Kaseforth Lucas Veverka. Eric Blake. - PowerPoint PPT PresentationTRANSCRIPT
Solar Sail
Department of Aerospace Engineering and Mechanics
AEM 4332W – Spacecraft Design
Spring 2007
2
Team Members
3
Solar Sailing:
4
Project Overview
5
Design Strategy
6
Trade Study Results
Orbit
Eric Blake
Daniel Kaseforth
Lucas Veverka
Eric Blake
Optimal Trajectory of a Solar Sail: Derivation of Feedback Control Laws
9
Recall Orbital Mechanics
• The state of a spacecraft can be described by a vector of 6 orbital elements.– Semi-major axis, a– Eccentricity, e– Inclination, i– Right ascension of the ascending node, Ω– Argument of perihelion, ω– True anomaly, f
• Equivalent to 6 Cartesian position and velocity components.
10
Orbital Elements
11
Equations of Motion
vr
nnrr
rr
v2^
2
^
2
^^^^
sinsincossincos rpprn
^
r
^
p
^^
rp
n
linesun
sail
= Sail Lightness Number = Gravitational Parameter
12
Problem: Minimize Transfer Time
1),,(2^
2
^
2
nnr
rr
rvuxH vvr
^
r
^
p
^^
rp
n
linesun
sail
^^^
353)(2))((2)(3 rnrnnnr
rrr
rr vrvr rv
^^
}max{ vv nn
By Inspection:
Transversality:
fttv
ttv npnr
rnpnr
r
2
^
22
^
2)()(
0
13
Solution
• Iterative methods are needed to calculate co-state boundary conditions.
• Initial guess of the co-states must be close to the true value, otherwise the solution will not converge.
• Difficult• Alternative: Parameter Optimization.
– For given state boundary conditions, maximize each element of the orbital state by an appropriate feedback law.
14
Orbital Equations of Motion
r
pTfSe
e
pr
df
dasin
)1(
222
2
e
p
rTf
p
rTfS
r
df
decos1sin
2
Wfp
r
df
di)cos(
3
Wfip
r
df
d)sin(
sin
3
f
p
rTfS
e
ri
df
d
df
dsin1coscos
2
12
2sin1cos1
f
p
rTfS
e
r
r
p
dt
df
)1( 2eap fe
pr
cos1
32
cosr
S sinsincos22r
T cossincos22r
W
),,( xgx
= Sail Lightness Number = Gravitational Parameter
15
Maximizing solar force in an arbitrary direction
^^^^
sinsincossincos rpprn ^^~~^~~^~
sinsincossincos rpprq
^
r
^
p
^^
rp
n
linesun
sail
Maximize:
qnnr
raq
2^
2
~
~
~2
tan4
tan893tan
Sail pointing for maximum acceleration in the q direction:
16
Locally Optimal Trajectories• Example: Use parameter optimization method to derive
feedback controller for semi-major axis reduction.
• Equations of motion for a:
r
pTfSe
e
pr
df
dasin
)1(
222
2
3
2cos
rS
sinsincos22r
T
fe
fe
cos1
sintan
~
fe
pr
cos1 )1( 2eap
2
~
~2
tan4
tan893tan
Feedback Law:
Use this procedure for all orbital elements
17
Method of patched local steering laws (LSL’s)
• Initial Conditions: Earth Orbit
• Final Conditions: semi-major axis: 0.48 AU inclination of 60 degrees
0
0
0
0
0
1
0tt
i
e
a
free
free
free
AU
i
e
a
tft
60
0~
48.0
18
Trajectory of SPI using LSL’s
Time (years)
19
20
Global Optimal Solution– Although the method of patched LSL’s is not ideal, it is a solution that is
close to the optimal solution.
– Example: SPI Comparison of LSL’s and Optimal control.
21
Conclusion
• Continuous thrust problems are common in spacecraft trajectory planning.
• True global optimal solutions are difficult to calculate.
• Local steering laws can be used effectively to provide a transfer time near that of the global solution.
Lucas Veverka
•Temperature
•Orbit Implementation
23
Daniel Kaseforth
Control Law Inputs and Navigation System
25
Structure
Jon T Braam
Kory Jenkins
Jon T. BraamStructures Group:
• Primary Structural Materials
• Design Layout
•3-D Model
• Graphics
28
Primary Structural Material
Weight and Volume Constraints• Delta II : 7400 Series • Launch into GEO
– 3.0 m Ferring» Maximum payload mass: 1073 kg» Maximum payload volume: 22.65 m3
– 2.9 m Ferring» Maximum payload mass: 1110 kg» Maximum payload volume: 16.14 m3
29
Primary Structural Material
Aluminum Alloy Unistrut– 7075 T6 Aluminum
Alloy• Density
– 2700 kg/m3
– 168.55 lb/ft^3
• Melting Point– ? Kelvin
Picture of Unistrut
30
Primary Structural Material
• Density
• Mechanical Properties– Allowing unistrut design
• Decreased volume
• Thermal Properties– Capible of taking thermal loads
31
Design Layout
• Constraints– Volume– Service task– Thermal consideration– Magnetic consideration– Vibration– G loading
32
Design Layout
• Unistrut Design– Allowing all inside surfaces to be bonded to
• Titanium hardware
– Organization• Allowing all the pointing requirements to be met with
minimal attitude adjustment
33
Design Layout
• Large Picture of expanded module
34
3-D Model
• Large picture
35
3-D Model
• Blah blah blah (make something up)
36
Graphics
• Kick ass picture
37
Graphics
• Kick ass picture
38
• The blanks will be filled in soon
39
Trade Studies
• Blah blah blah
40
Why I deserve an “A”
• Not really any reason but when has that stopped anyone!
Kory Jenkins• Sail Support Structure• Anticipated Loading•Stress Analysis• Materials•Sail Deployment
42
Attitude Determination and Control
Brian Miller
Alex Ordway
Brian Miller
•Tip Thrusters vs. Slidnig Mass
•Attitude Control Simulation
Alex Ordway60 hours worked
Attitude Control Subsystem Component Selection and
Analysis
46
Design Drivers
• Meeting mission pointing requirements
• Meet power requirements
• Meet mass requirements
• Cost
• Miscellaneous Factors
47
Trade Study
• Sliding Mass vs. Tip Thruster Configuration– Idea behind sliding mass
48
Trade Study
• Sliding mass ACS offers– Low power consumption (24 W)– Reasonable mass (40 kg)– Low complexity– Limitations
• Unknown torque provided until calculations are made• No roll capability
• Initially decided to use combination of sliding mass and tip thrusters
49
ADCS System Overview
• ADS– Goodrich HD1003 Star Tracker primary– Bradford Aerospace Sun Sensor secondary
• ACS– Four 10 kg sliding masses primary
• Driven by four Empire Magnetics CYVX-U21 motors
– Three Honeywell HR14 reaction wheels secondary
– Six Bradford Aero micro thrusters secondary• Dissipate residual momentum after sail release
50
ADS
• Primary– Decision to use star tracker
• Accuracy• Do not need slew rate afforded by other systems
– Goodrich HD1003 star tracker• 2 arc-sec pitch/yaw accuracy• 3.85 kg• 10 W power draw• -30°C - + 65 °C operational temp. range• $1M
– Not Chosen: Terma Space HE-5AS star tracker
51
ADS
• Secondary– Two Bradford Aerospace sun sensors
• Backup system; performance not as crucial• Sensor located on opposite sides of craft• 0.365 kg each• 0.2 W each• -80°C - +90°C
52
ACS
• Sliding mass system– Why four masses?– Four Empire Magnetics CYVX-U21 Step Motors
• Cryo/space rated• 1.5 kg each• 28 W power draw each 200 °C
• $55 K each• 42.4 N-cm torque
53
ACS
• Gear matching- load inertia decreases by the gear ratio squared. Show that this system does not need to be geared.
2
2
2170 (600sec)
20.00389
(10 )(0.00389 )
0.0389
ms
ms
m a
a
F ma kg
F N
54
ACS
• Three Honeywell HR14 reaction wheels– Mission application– Specifications
• 7.5 kg each• 66 W power draw each (at full speed)• -30ºC - +70ºC• 0.2 N-m torque• $200K each• Not selected
– Honeywell HR04– Bradford Aerospace W18
55
ACS
• Six Bradford micro thrusters– 0.4 kg each– 4.5 W power draw each– -30ºC - + 60ºC– 2000 N thrust
– Supplied through N2 tank
56
Attitude Control
• Conclusion– Robust ADCS
• Meets and exceeds mission requirements• Marriage of simplicity and effectiveness• Redundancies against the unexpected
Power, Thermal and Communications
Raymond Haremza
Michael HitiCasey Shockman
Raymond HaremzaThermal Analysis
•Solar Intensity and Thermal Environment•Film material•Thermal Properties of Spacecraft Parts•Analysis of Payload Module•Future Work
59
Casey ShockmanCommunications
61
Michael HitiPower
63
64
Demonstration of Success
65
Future Work
66
Acknowledgements
• Stephanie Thomas
• Professor Joseph Mueller
• Professor Jeff Hammer
• Dr. Williams Garrard
• Kit Ru….
• ?? Who else??