Marco Concha Charles Petruzzo June 28, 2001 SuperNova/ Acceleration Probe (SNAP) Flight Dynamics.

Marco ConchaCharles Petruzzo

June 28, 2001

SuperNova/ Acceleration Probe (SNAP)

Flight Dynamics

SNAP, June 25-28, 2001Goddard Space Flight Center

Flight Dynamics

Flight Dynamics Topics

Driving Requirements and Assumptions Orbit Comparison Table Prometheus Prometheus Circular Deployment Scenarios Tracking Visibility Scenarios Trades to Consider Issues and Concerns


Flight Dynamics

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.


Flight Dynamics

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


entry


entry


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


s exist


s exist <1 hour <1.5 hours <2 hours>4 hrs

1 event/yr TBD1. Radiation % loss figures source: SNAP pre-work

Orbit


Flight Dynamics

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


Flight Dynamics

Fly-by Scenarios

Non Encounter

Leading Edge: Lower perigee

Trailing Edge: Raise perigee

Very Near Encounter !


Flight Dynamics

Tracking Visibility Scenarios

0, 20, 40, 65 degrees inclination

3 stations: Tokyo, Berkeley, Lyon

5 stations: Tokyo, Berkeley, Lyon, Hawaii, Santiago


Flight Dynamics

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


Flight Dynamics

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

)


Flight Dynamics

Trades to Consider

Tracking Coverage Number of stations versus Coverage Gaps

Prometheus Orbit Apogee DV to Lower Apogee (Propellant mass) versus Mass to

Orbit


Flight Dynamics

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.

Marco Concha Charles Petruzzo June 28, 2001 SuperNova/ Acceleration Probe (SNAP) Flight Dynamics.

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Transcript of Marco Concha Charles Petruzzo June 28, 2001 SuperNova/ Acceleration Probe (SNAP) Flight Dynamics.