QB50 Proposed Deployment ConOps. Dan Oltrogge Center for Space Standards and Innovation Co-Lead, QB50 Orbit Dynamics Working Group

Transcription

1 QB50 Proposed Deployment ConOps Dan Oltrogge Center for Space Standards and Innovation Co-Lead, QB50 Orbit Dynamics Working Group 25 Apr 2014

2 Proposed QB50 Deployment ConOps Want to develop and characterize QB50 deployment, seeking to optimize multi-objective function Maximize post-deployment miss distance Maximize Inter-QB50 in-plane separation rate Minimize orbit lifetime disparity between all QB50 sats Maximize QB50 orbit lifetime Minimize probability of collision and manned operations impact QB50 launcher is now official: Cyclone-4 Cyclone-4 LV User s Guide, Oct 2010, Alcantara Cyclone Space 4_user s_guide_oct_2010_v02.pdf Pg 2

3 Cyclone-4 Characteristics Liquid Jet System (LJS) (p.35) lifetime = 6 hours LJS prior to Stage III ignition performs coast ACS + axial accel to prepare fuel for Stage III. LJS during Stage III controls roll orientation LJS post-stage III performs ACS for s/c separation, ACS for coast, deorbit maneuver, and ACS for deorbit LJS nominal thrust 100 N Stage III mass 4300 kg LJS Isp 190 seconds Orbit errors (p. 35) for SSO 700 km: Δh = ±7 km; Δinc = ±0.08 ; Δω = ±10 Estimated that the mass of the entire QB50 sled plus all of the QB50s should not exceed 300 kg. That puts the combined mass (Upper Stage + QB50) at start of deployment at 4600 kg. Pg 3

4 QB50 QuadPack QB50 deployment performed by the ISIS QuadPack Fine-grained deployment timing Cyclic deployment NORMAL to in-track during Cyclone4 upper stage thrusting: e.g. for Thr(αRTN,δRTN)= (0,90 ), ΔVs = (0,90 ), (0,-90 ), (0,90 ), (0,- 90 ), etc. Pg 4

5 Parametric Relative Motion Analyses A combination of the 1Earth RELative MOtion (RELMO) tool and STK were used to conduct the analysis. RELMO numerically models lift, drag, SRP, thrust, J2-J7 Relative motion computed in inertial frame without simplification or reduction to relative frame(s) Conducted thousands of RELMO analyses to characterize miss distance and ISS risk STK used to visualize RELMO trajectories and verify RELMO separation results Incorp. Errors: CD (±4%), Spring ΔV (±7%), F10.7 (±8%) Pg 5

6 Parametric Time of Global Closest Approach The time of closest approach between ALL QB50 sats as a function of Cyclone Upper Stage Thrust direction Pg 6

7 Parametric Global Closest Approach The global closest approach between all QB50 satellites maximized for off-back-track Cyclone 4 thrusting Pg 7

8 Parametric Inter-QB50 Drift Rate The drift rate between consecutive QB50 satellites is maximized by along-track Cyclone 4 thrusting Pg 8

9 Parametric Individual QB50 Lifetime QB50 orbit lifetime is 2 to 4 months. Pg 9

10 QB50 Risk To Other Operators There are at least five different probability metrics established for likelihood of impacting other missions: 1. PPRED: Probability that a predicted conjunction event, coupled with approach geometry and estimated positional uncertainty, will actually result in a hardbody collision 2. PMAX: Max possible probability that a predicted conjunction event, coupled with approach geometry, could result in a collision, irrespective of knowledge of positional uncertainty 3. PACTUAL: The estimated actual collision probability as represented by idealized orbits and/or occupied ring-shells 4. POI: Probability of Operational Impinging other operator(s) 5. PAM: Probability of Avoidance Maneuver by other operator Pg 10

11 ISS Operations From NASA ISS Trajectory Operations and Planning (TOPO) Office: In the past 2 years, ISS has climbed from ~350 Km to ~410 Km. That s semi-major axis (SMA) altitude. In that timeframe, our lowest perigee was ~335 Km in June 2011 while our highest apogee was ~435 Km in September We expect for the next 6-12 months to stay in approximately the same range we are now (max Ha/min Hp of ~430/400 Km), but we haven t worked out specifics for after that. It is possible that we may drag down a little lower, perhaps even as low as ~380 Km SMA but that is not firm. Pg 11

12 ISS Altitude Profiles STS End-of-Mission Permitted ISS Orbit Raise. But 380 km perigee is still a possibility, and CelesTrak results clearly shows current 400 km perigee. Pg 12

13 PACTUAL: Probability of QB50 Collision With ISS If start thrusting too high, introduce non-zero PCOLL w/iss Pg 13

14 POI: Probability of QB50 Impinging on ISS Operations If start thrusting too high, can impinge on ISS operations Pg 14

15 Thrust Direction Multi-Obj Fn Optimization Now have all the components to optimize Cyclone-4 thrust direction during deployment Penalize if any QB50 satellites get closer than 250m WMD = [250m / Miss Distance] Penalize if intra-qb50 angular drift rate < 0.2 per day WDRIFT = [0.2 / drift rate] Penalize if orbit lifetimes shorter than 3.5 months (110 days) WLIFETIME = [110 days / minimum lifetime] Penalize if orbit lifetimes disparate between QB50s>20 days Penalize if PACTUAL>1.e-6 and if POI>1.e-4 WACTUAL = [PACTUAL / 1.e-6] and WOI = [POI / 1.e-4] Want to maximize M.O.F. = 1. / Wi Mutually Exclusive! Pg 15

16 Optimal Cyclone-4 Thrust Direction Based upon M.O.F., optimal thrust direction determined to be in in-plane, along-velocity direction Pg 16

17 What s a bad deployment scheme look like? Bad deployment scheme fails to provide temporal separation, prelaunch predictability, collision avoidance Pg 17

18 QB50 Deployment STK Scenario Cyclone-4 along-velocity thrusting scenario created Contains all 50 QB50 satellites plus the Cyclone-4 Upper Stage AGI providing authoritative STK scenario to all QB50 participants and relevant tracking entities Pg 18

19 QB50 Deployment STK Scenario Deployment scenario still evolving but likely to be: Pg 19

20 Conclusions QB50 deployment scheme is a work in progress Deployment using Cyclone 4 LJS along-velocity thrust during 18 minute deployment from 355 km depicted This scheme maximizes in-plane separation & discrimination while minimizing probability of collision, ISS operational load and ISS risk Deployment sequence remains < ISS altitude for ALL QB50s Not sufficient to only consider collision risk; also must factor in liability, risk to life, operational impact Questions?? Pg 20