Upload
prosper-hart
View
213
Download
1
Embed Size (px)
Citation preview
Marco ConchaCharles Petruzzo
June 28, 2001
SuperNova/ Acceleration Probe (SNAP)
Flight Dynamics
SNAP, June 25-28, 2001Goddard Space Flight Center
Flight Dynamics Page 2
Flight Dynamics Topics
Driving Requirements and Assumptions Orbit Comparison Table Prometheus Prometheus Circular Deployment Scenarios Tracking Visibility Scenarios Trades to Consider Issues and Concerns
SNAP, June 25-28, 2001Goddard Space Flight Center
Flight Dynamics Page 3
Driving Requirements and Assumptions
View North and South Ecliptic Poles Maximize Downlink capability (coverage and rate) Prometheus Orbit Scenario
19 x 57 Re mission orbit lunar swingby deployment source: High Earth Orbit Design for Lunar-Assisted
Medium Class Explorer Missions, McGiffen, D. A. and Matthews, M., 2001 Flight Mechanics Symposium, NASA Goddard Space Flight Center.
SNAP, June 25-28, 2001Goddard Space Flight Center
Flight Dynamics Page 4
Options ConsideredOrbit Comparison Table
Requirement LEO Sun-sync 1 x 10.2 2 x 19.2 3 x 18.2
Molniya (279 x 6.3 Re) alt
Molniya (1500 x 11 Re) alt
Molniya (3 x 8.2) alt
Prometheus Long
Prometheus Circular (40 Re)
Lifetime (>5 years) yes yes yes yes likely yes yes yes yes
Radiation Belt Avoidance yes 33% loss1 16% loss1 20% loss1 35 % loss1 30 % loss1 25 % loss1 yes yesHeritage yes no no no yes TBD TBD no no
Tracking Coverage Gaps (Tokyo,Berkeley,Lyon) manageable TBD TBD TBD manageable manageable manageable
(0-35 hrs) depend on inclination TBD
Magnetic ACS Usable yes not likely no no TBD TBD TBD no no
Disposal
likely to be controlled re-
entry TBD TBD TBD
likely to be controlled re-
entry
likely to be controlled re-
entry
likely to be controlled re-
entry no no
Deployment DV low TBD TBD TBD TBD TBD TBDlow w/lunar
swingby highMission Orbit Corrections yes TBD not likely not likely no noEarth Thermal Radiation Avoidance yes TBD no no yes yes yes no yesEarth Occultation Avoidance no yes yes yes no no TBD yes yes
Eclipseone season/
year
>2 hrs possible, favorable candidate
s exist
>4 hrs possible, favorable candidate
s exist
>4 hrs possible, favorable candidate
s exist <1 hour <1.5 hours <2 hours>4 hrs
1 event/yr TBD1. Radiation % loss figures source: SNAP pre-work
Orbit
SNAP, June 25-28, 2001Goddard Space Flight Center
Flight Dynamics Page 5
Prometheus Orbit
“Prometheus Long” source:
1.High Earth Orbit Design for Lunar-Assisted Medium Class Explorer Missions, McGiffen, D. A. and Matthews, M., 2001 Flight Mechanics Symposium, NASA Goddard Space Flight Center.
2. Mission Feasibility Study for the KRONOS High Earth Orbit, McGiffen, D. A. and Matthews, M., CSC-96-968-19, NASA Task Order S-32415-G, 2000.
Pros Above Van Allen Belts No orbit corrections required during mission orbit No Earth occultation Eclipse seasons: typically one event per year
Cons Can’t use torque rods for momentum management; Propulsion? Tracking gaps (0-35 hours dependant on inclination, station
configuration) Difficult to analyze and design but lunar flyby not a new
technique Lifetime Goal TBD refer to KRONOS paper Disposal TBD refer to NSS 1740.14
SNAP, June 25-28, 2001Goddard Space Flight Center
Flight Dynamics Page 6
Fly-by Scenarios
Non Encounter
Leading Edge: Lower perigee
Trailing Edge: Raise perigee
Very Near Encounter !
SNAP, June 25-28, 2001Goddard Space Flight Center
Flight Dynamics Page 7
Tracking Visibility Scenarios
0, 20, 40, 65 degrees inclination
3 stations: Tokyo, Berkeley, Lyon
5 stations: Tokyo, Berkeley, Lyon, Hawaii, Santiago
SNAP, June 25-28, 2001Goddard Space Flight Center
Flight Dynamics Page 8
Coverage Example: 3 Stations
0
3
6
9
12
15
18
0 14 28 42 56 70 84
Days Since Epoch Date
Co
vera
ge
Gap
in H
ou
rs
Coverge Gap Example: Berkeley, Lyons, Tokyo
7 x 66 e.r. I ncl = 40 deg
Epoch = Oct 1, 2008Apogee Radius = 66 e.r.Perigee Radius = 7 e.r.Inclination = 40 degArgP = 0RAAN = 0True Anomaly = 0Propagation was Keplerian
0
5
1 0
1 5
2 0
2 5
3 0
3 5
4 0
0 1 4 2 8 4 2 5 6 7 0 8 4
D ay s S ince E p o ch D ate
Co
ve
rag
e G
ap
in
Ho
urs
Coverge Gap Example: Berkeley, Lyons, T okyo
7 x 66 e. r. I ncl = 65 deg
E p o c h = O c t 1 , 2 0 0 8A p o g e e R a d iu s = 6 6 e .r .P e r ig e e R a d iu s = 7 e .r .In c lin a tio n = 6 5 d e gA r g P = 0R A A N = 0T r u e A n o m a ly = 0P r o p a g a tio n w a s K e p le r ia n
0
1
0 1 4 2 8 4 2 5 6 7 0 8 4
D a y s S in c e E p o c h D a t e
Co
ve
rag
e G
ap
in
Ho
urs E p o c h = O c t 1 , 2 0 0 8
A p o g e e R a d iu s = 6 6 e .r .P e r ig e e R a d iu s = 7 e .r .In c lin a t io n = 0 d e gA r g P = 0R A A N = 0T r u e A n o m a ly = 0P r o p a g a tio n w a s K e p le r ia n
(n o g a p s )
Cover ge Gap E x ample: Ber keley, Lyons, T okyo
7 x 66 e. r . I ncl = 0 deg
0
1
2
3
4
5
0 1 4 2 8 4 2 5 6 7 0 8 4
D a y s S in c e E p o c h D a t e
Co
ve
rag
e G
ap
in
Ho
urs
Coverge Gap Example: Berkeley, Lyons, T okyo
7 x 66 e. r . I ncl = 20 deg
E p o c h = O c t 1 , 2 0 0 8A p o g e e R a d iu s = 6 6 e .r .P e r ig e e R a d iu s = 7 e .r .In c lin a tio n = 2 0 d e gA r g P = 0R A A N = 0T r u e A n o m a ly = 0P r o p a g a tio n w a s K e p le r ia n
SNAP, June 25-28, 2001Goddard Space Flight Center
Flight Dynamics Page 9
Prometheus Circular Orbit
DV to lower apogee Initial State: 40 Re x 63 Re Assuming a fly-by can raise
perigee to 40 Re (instead of baseline 19 Re)
Model Hohman Transfer DV to lower apogee
Impulsive thrust modeled; in reality may require multiple burns
To achieve a 40 Re circular orbit would require a 136 m/s burn.
Propellant Required
DV = 136 m/s Isp = 220 sec Minitial = 1600 kg
Mprop = 96 kg
DV Required to Lower Apogee Initial Orbit: 40 x 63 Re
30
35
40
45
50
55
60
0 50 100 150 200 250DV (m/s)
Fin
al
Ap
og
ee
(R
e)
initialgI
V
Me sp
D
1
Propellant Mass Required to Lower Apogee : Initial Orbit: 40 x 63 Re
30
35
40
45
50
55
60
0 50 100 150 200
Propellant Mass (kg)
Fin
al A
po
ge
e (
Re
)
SNAP, June 25-28, 2001Goddard Space Flight Center
Flight Dynamics Page 10
Trades to Consider
Tracking Coverage Number of stations versus Coverage Gaps
Prometheus Orbit Apogee DV to Lower Apogee (Propellant mass) versus Mass to
Orbit
SNAP, June 25-28, 2001Goddard Space Flight Center
Flight Dynamics Page 11
Issues and Concerns
Refer to TBD’s in Orbit Comparison Table Lunar swingby
Transfer to mission orbit via swingby - How high can perigee be raised? What is the maneuver precision and risk mitigation required for this limit?
Analytically intensive, will require high degree of skill. Iterative design process is slow, will limit solution space. Optimal solution may be elusive.