Lunar Missions: Earth-orbiting or Planetary?

Transcription

1 NASA Cost Symposium, 2018 Export Control Notice Export or re-export of information contained herein may be subject to restrictions and requirements of U.S. export laws and regulations and may require advance authorization from the U.S. Government. Lunar Missions: Earth-orbiting or Planetary? Mitch Lasky, Ball Aerospace Joe Hamaker, PhD, Galorath Federal (With Special Thanks to Mary Ellen Harris, the MSFC REDSTAR Librarian)

2 Contents 2 Motivation Purpose Orbit Descriptions Earth-orbiting, Lunar, Planetary Mission Characteristics Parametric Analysis Historical Cost Analysis Observations

3 Motivation - Exploration 3

4 Lunar Exploration Missions 4

5 Power and Propulsion Element 5

6 NASA Exploration Campaign 6

7 Motivation 7 There is a need to credibly estimate cost of lunar orbital and EM L1, L2 missions Parametric models typically allow selection of Earthorbiting or planetary mission Which results in a more credible cost estimate for lunar missions? This study excludes lunar landers

8 Purpose 8 This presentation will: Explore characteristics of Earth-orbiting, lunar orbiting, EM L1, L2, and planetary orbits and what drives spacecraft design and cost Compare results of parametric cost estimates for spacecraft using Earth-orbiting and planetary input selections Analyze historical spacecraft cost and mass to determine if there is a statistically valid difference in Earth-orbiting, lunar orbiting, and planetary mission cost Provide near- and long-term suggestions for lunar orbital and EM L1, L2 cost estimates

9 Orbit Description: Earth-orbiting 9 Distance from Earth LEO 160 2,000 km HEO 16,000 x 133,000 km MEO 2,000 35,786 km GEO 35,786 km Not to scale

10 Orbit Description: Lunar 10 EM L2 ~449,000 km Low Lunar Orbit (LLO) 100 km Mean distance 384,450 km EM L1 ~326,400 km ~58,030 km Apogee: 405,504 km Perigee: 363,396 km Not to scale

11 Orbit Description: Planetary 11 Distance from Earth (closest approach) Venus 40 M km Mars 56 M km Moon 0.36 M km GEO M km

12 Lunar Orbit 12 Model as Earth-orbiting or Planetary? 0.36 M km Moon Mars Lunar GEO M km 56 M km E-M L1 E-M L2 Not to scale Answer requires more information than distance from Earth

13 Differences Between Earth-orbiting, Lunar Orbital, and Planetary Missions 13 Propulsion LEO: optional, rare Planetary: required to reach destination Lunar: required to reach destination Telecom/ADC Pointing/Ground Station Tracking LEO: slew s/c or gimbal antenna Planetary: large distances require fine pointing Lunar: Distance not as great as Planetary; fast slewing not required RF Transmit Power Range dependent o Planetary > Lunar > LEO o Increased mass (and cost) for TWTA and conditioning electronics

14 Differences Between Earth-orbiting, Lunar Orbital, and Planetary Missions 14 Thermal Control & Battery Degradation Eclipse Cycle LEO: ~14 eclipses/day Planetary: destination dependent Lunar: ~14 eclipses/day, some may be long Destination Dependence Distance from sun Distance from Sun (AU) Solar Flux Solar Flux (W/m 2 ) [Earth=1] Body (W/m 2 ) Earth Moon Venus Mars Jupiter

15 Differences Between Earth-orbiting, Lunar Orbital, and Planetary Missions 15 Autonomy (FSW) Time delay proportional to range Planetary > Lunar > LEO Number of contacts depends on destination and ground infrastructure Anomaly may become mission critical failure if response not timely Autonomy may buy critical time

16 Differences Between Earth-orbiting, Lunar Orbital, and Planetary Missions 16 Delta-v/Mass Constraint LEO: Least constrained Δv ~9 km/s Planetary: Largest delta-v required -> more fuel -> reduced s/c mass (exotic materials, non-standard manufacturing processes) -> higher cost Mars Δv ~15-19 km/s Lunar Δv ~13 km/s Critical Propulsive Events LEO: none Planetary: can be several Parker Solar Probe has 5 Venus gravity assists Lunar: Orbit injection Periodic orbit maintenance o Asymmetric lunar density resulting in non-uniform gravitational field

17 Differences Between Earth-orbiting, Lunar Orbital, and Planetary Missions 17 NASA Mission Class LEO Typically Class C or Class D Planetary Typically Class B or Class C Lunar Some Class D LCROSS, LADEE Less stringent parts requirements Full-redundancy may not be required Some Class B GRAIL, LRO

18 Destination Comparison 18 Parameter Propulsion Telecom Pointing/Gnd Stn Trkg Telecom Range Battery Degradation Autonomy (FSW) Thermal Control Mass Constraint Delta-V (Inner Planets) Critical Propulsive Events 1=> more benign

19 Destination Comparison 19 Destination Parameter Earth-Orbiting Lunar Planetary Propulsion Telecom Pointing/Gnd Stn Trkg Telecom Range Battery Degradation Autonomy (FSW) Thermal Control Mass Constraint Delta-V (Inner Planets) Critical Propulsive Events Total Lunar total not closer to Earth-orbiting or planetary totals Destination driven characteristics imply lunar orbital mission cost is probably between Earth-orbiting and planetary mission costs 1=> more benign

20 Parametric Models: Spacecraft 20 Modeling methodology 4 different models Results estimated for Earth-orbiting Planetary Identical spacecraft MEL used Results normalized to Earth-orbiting cost Parametric Relative Spacecraft Cost Model Earth-orbiting Planetary SSCM Commercial PCEC QuickCost Average Planetary to Earth-orbiting cost: 1.3

21 Lunar Orbiting: Earth-orbiting or Planetary? 21 Based on qualitative mission requirement differences between Earth-orbiting, lunar, and planetary missions Lunar orbital and EM L1, L2 mission requirements are a composite of Earth-orbiting and Planetary mission requirements 30% cost increase over Earth-orbiting mission estimated by a parametric model may be not be justified (Planetary model input selected) What can we learn from the historical data?

22 Recap of 2017 Cost Results 22 In our 2017 study, we found that Planetary Missions cost more per unit of mass than Earth Orbital and the difference could be shown to be statistically valid with t-tests and regression analysis Well duh We only did this test to warm up our t-test jets We then showed that Lagrange missions were statistically more birds of a feather with Earth Orbital Missions than they were with Planetary Again, using t-tests and regression

23 Methodology Differences From 2017 Study 23 Our 2017 study of Lagrange missions used Life cycle cost of the missions (Phase B/C/D/E) Including Launch Costs Dollars per wet kg (because of missing dry mass data) This 2018 study of Lunar missions used Phase B/C/D (not including Phase E) Excluding Launch Costs And dollars per dry kg (we filled in missing dry mass numbers) Why? Because Phase E, Launch Costs and dollars per wet kg added noise to the data Plus we re-categorized Lagrange missions as Earth Orbital based on the results from our 2017 study

24 Is There A Difference In Cost? 24 First, we will compare the mean $/Dry kg of the three destinations Used mean $/Dry kg (i.e., as opposed to just mean $) to correct for the scale difference in the missions Two sample t-tests were used to investigate if there is a difference in the mean cost of Earth Orbital and Planetary missions (just to warm our t-test jets) Lunar vs Earth Orbital missions Lunar vs Planetary missions We will also use regression analysis to examine the predicted cost of the three destinations

25 Cost Database (Showing Only Lunar Missions in the Table) 25 FY2018$Ms Mass (kg) Mission Phase B/C/D Acquisition Cost Less Launch Cost* Wet Dry Orbit Launch Year Organiza tion(s) Other Explorer 33 (AKA IMP-D) $ Lunar Jul-66 NASA GSFC Explorer 35 (AKA IMP-E) $ Lunar Jul-67 NASA LaRC Explorer 49 (AKA RAE-B) $ Lunar Jun-73 NASA (Center TBD) Clementine $ Lunar Jan-94 NASA, Lunar Prospector $ Lunar Jan-98 NASA Ames Lockheed Martin Lunar CRater Observation and Sensing Satellite (LCROSS) $ Lunar Jun-09 NASA ARC Gravity Recovery and Interior Laboratory (GRAIL)* $ Lunar Sep-11 JPL Lunar Reconaissance Orbiter (LRO) $ Lunar Sep-13 NASA GSFC Lunar Atmosphere and Dust Environment Explorer (LADEE) $ Lunar Sep-13 ARC, * For multi-spacecraft missions the costs reflect only Development through the First Unit Our database consisted of 71 missions 42 Earth Orbital (including Lagrange missions) 20 Planetary 9 Lunar (shown in table above) including 9 Orbital and 4 missions at L1 and L2 Note: We left out a few available historical lunar missions which seemed to be outliers Surveyor (1966) was a Lunar lander Lunar Orbiter (1966) was a very expensive mission (~$1 billion in today s dollars) Artemis P1 was a relocated THEMIS B (2007) spacecraft

26 First Indications 26 Destination $/Dry Kg Ratio to Earth Orbital Earth Orbital (including Lagrange) $536, Lunar Orbit $685, Planetary $765, A simple dollars per dry kg calculation indicates that per kg Lunar missions cost 1.28x Earth Orbital Planetary missions cost 1.43x Earth Orbital

27 T-Test Comparing Earth Orbital and Planetary Missions 27 Two-sample T for $/dry kg EO=0, PL=1 N Mean StDev SE Mean Difference = mu (0) - mu (1) Estimate for difference: % CI for difference: ( , ) T-Test of difference = 0 (vs not =): T-Value = P-Value = DF = 28 Earth Orbital mean $/kg is $229,055 less than Planetary It could range from $418,877 down to $39,234 less than Planetary (95% CI) CI does not span across zero which would cast doubt P = 0.02 says we are ~98% confident So this is again, well duh we all know Planetary > Earth Orbital (all else held equal)

28 T-Test Comparing Lunar and Earth Orbital Missions 28 Two-sample T for $/dry kg EO=0, Lunar=1 N Mean StDev SE Mean Difference = mu (0) - mu (1) Estimate for difference: % CI for difference: ( , ) T-Test of difference = 0 (vs not =): T-Value = P-Value = DF = 9 Earth Orbital mean $/kg is $173,545 less than Lunar But it could range from $412,084 less to $64,995 more than Lunar (95% CI) The CI spans across zero which casts doubt P = does not meet the usual p<0.05 standard So all this is saying that we are not sure Earth Orbital missions are less than Lunar missions

29 T-Test Comparing Lunar and Planetary Missions 29 Two-sample T for $/dry kg Lunar=0, PL=1 N Mean StDev SE Mean Difference = mu (0) - mu (1) Estimate for difference: % CI for difference: ( , ) T-Test of difference = 0 (vs not =): T-Value = P-Value = DF = 15 Lunar mean $/kg is $7,143 less than Planetary But it could range from $237,250 more to $385,536 less than Lunar (95% CI) The CI spans across zero which casts doubt P = 0.51 does not meet the usual p<0.05 standard So all this is saying that we are not sure that Lunar missions are less than Planetary missions

30 Regression Analysis 30 The regression equation is $/dry kg = Total Dry Mass (kg) Predictor Coef SE Coef T P Constant Total Dry Mass (kg) The regression equation is $/dry kg = Total Dry Mass (kg) EO=0, PL=1 Predictor Coef SE Coef T P Constant Total Dry Mass (kg) EO=0, PL= The regression equation is $/dry kg = Total Dry Mass (kg) EO Lunar Predictor Coef SE Coef T P Constant Total Dry Mass (kg) EO Lunar First box, CER with dry mass only passes t-test (p=0.022) Second box, CER with dry mass plus Planetary indicator variable passes t-test (p=0.049 and 0.009) Third box, CER with dry mass plus indicator variables for Earth Orbital, Lunar & Planetary Planetary was too correlated with Lunar to fight its way in Lunar stayed in but with a poor p value (0.315)

31 Conclusions from Statistical Analysis 31 Planetary missions remain statistically significantly more expensive (all else held equal) than earth orbital missions There s that well duh again From just a $/Dry kg perspective, it appears that Lunar missions might be ~1.28x Earth Orbital And Planetary missions ~ 1.43x Earth Orbital But the t-tests compared the mean $/dry kg of the three destinations and failed to find them statistically significantly different And likewise, the regression analysis did not find the three destinations to be statistically significantly different This analysis had only 9 lunar missions to consider And three of those had to be unearthed from their moldy graves (Again special thanks to Mary Ellen Harris, the MSFC REDSTAR Librarian) Until more lunar data is available, it is difficult to be statistically conclusive about the costs of Lunar Missions relative to Earth Orbital and Planetary Missions

32 Observations 32 Mission characteristics comparison does not strongly indicate lunar mission more similar to Earth-orbiting or planetary mission There may be a 30% cost increase from Earth-orbiting when selecting Planetary for spacecraft parametric models Lunar orbital missions may not warrant this incremental cost due to mission requirements Statistical analysis of historical data does not strongly support correlation between Earth-orbiting and lunar orbital missions or planetary missions and lunar orbital missions Dollars per kilogram analysis indicates lunar orbital missions may be 28% greater than Earth-orbiting missions and 15% less than planetary missions

33 Suggestions 33 Near-term Conservative option is to model lunar mission as Planetary Lunar mission may not warrant 30% planetary tax Model lunar orbital missions as Earth-orbiting or somewhere between Earth-orbiting and planetary Long-term Recommend parametric model developers collaborate with NASA and Industry to analyze available cost and technical data to recommend model input settings for lunar orbital missions

34 Questions? 34 Pink Floyd