Lessons from Surveyor 6: Hopping Spacecraft for Low-Cost Surface Mobility on Small Bodies Niko Romer, Art Chmielewski, Nathan Barba, Nathan Fulmer. March 5, 2019 IEEE 2019 Aerospace Conference Copyright 2019 California Institute of Technology. U.S. Government sponsorship acknowledged. ~90 km

~20km Total distance driven by Curiosity in 6.5 years on Mars.

jpl.nasa.gov ~90 km ~600 km ~20km

3 jpl.nasa.gov PlanetarySociety.com Why Hop?

• Great scientific value in characterizing multiple regions. • Travel farther, faster, and cheaper than rovers. • Two types of hops can be considered: – Mechanical – Propulsive

March 5, 2019 4 jpl.nasa.gov Hopping Categorized – Mechanical

Agency Mission S/C Year Destination

USSR Phobos 2 PROP-F 1988 Phobos

JAXA Hayabusa MINERVA 2005 Itokawa http://cyberneticzoo.com/walking- machines/1983-7-prop-fphobos- hopper-soviet/ JAXA/ Hayabusa 2 MINERVA- 2018 Ryugu JAXA DLR II/MASCOT

DLR Rosetta Philae 2015 Comet 67P

ESA NASA N/A Hedgehog In Many possible dev.

NASA/JPL-Caltech/Stanford March 5, 2019 5 jpl.nasa.gov Hopping Categorized – Propulsive

UMD/GSFC/NASA NASA/GRC • Chopper (Comet Hopper), NASA Goddard • Mars Geyser Hopper, NASA Glenn - Discovery Class Proposal for - Discovery mission concept launch in 2016

March 5, 2019 6 jpl.nasa.gov 7 jpl.nasa.gov Surveyor Program: • Seven Pre-Apollo robotic scouts. • Program ran from 1966-1968.

LEM

Astronaut Pete Conrad

Surveyor 7

8 jpl.nasa.gov NASA/JPL-Caltech Surveyor 6 (1967)

First (and only until October 2018) successful hop on the surface of another body. • Soft lander for Lunar Surface • Dry Mass – 300 kg • ~16kg of excess propellant not used during initial soft landing. • Engineers performed a ”hop experiment.” • 2.5 second fire of ACS thrusters. • Average thrust 1390 N at +7° pitch. • Rose 4 m vertically, and translated 2.5 m horizontally.

March 5, 2019 NASA/JPL-Caltech 9 jpl.nasa.gov Surveyor Model

5 Coast • We modeled a two-burn hop trajectory using a “Surveyor-like” 300 kg spacecraft. 4.5 �, • Surface curvature is ignored in this

4 model. • For both models in this study, ∆v is the 3.5 required initial velocity for a distance ∆s. 3 Δ�% Δ�& #!'( 2.5 Δ� = Δ� + Δ� = 2 !"!#$ % & ()*&+ 2 α Δ� � − gravity Δ� − initial burn 1.5 Δ� − distance of hop Δ� − Retrobraking burn 1 � − launch angle -2 -1.5 -1 -0.5 0 0.5 1 1.5 2

March 5, 2019 10 jpl.nasa.gov Jump and Wait – An alternative hopping method

• This method involves rising to an altitude h and waiting for the planet or body to rotate underneath the spacecraft.

• Jump and Wait can save some fuel on fast-rotating bodies with low gravity.

" '(## Δ� = 2 ! !"!#$ -.()*/

�! − gravity � − mean radius of body Fulmer, 2017

� − polar angle �", �# − moment arms from Δ� − distance of hop rotational axis � − angular rate of rotation ℎ − maximum altitude

March 5, 2019 11 jpl.nasa.gov Comparing Jump-and-wait with Hopping

Example: Hopping on Ceres To determine when Jump and wait will save fuel on the equator: Jump and Wait becomes more efficient $ & ∆ % < %

� < �� , � = 2 ∆�

Δ� − distance of hop � − Angular rate of rotation

March 5, 2019 12 jpl.nasa.gov Body GM (km^3/s^2)mean radiusPlanet (km) Gravity Rotation(m/s^2) rate (rad/s)JW1000JW2000JW10000JW20000 Ceres 62.6284 469.7 0.283876993 0.0001923 94 119 203 256 67P 6.661E-07 2 0.000166514 0.0001368 0.7 0.93 1.59 6.24 Moon 4902.801 1737.5 1.624032214 2.662E-06 ### 1583 2706 #### Triton 1427.6 1353.4 0.779388862 1.237E-05 461 581 994 3891 Phobos 0.000711 11.1 0.005772259 0.0002279 6.6 8.36 14.3 56 Deimos 9.85E-05 6.2 0.002562435 5.76E-05 6.1 7.7 13.2 51.5 Europa 3202.739 1560.8 1.314701128 2.048E-05 553 696 1191 4661 Ganymede 9887.834 2631.2 1.428214526 1.016E-05 738 929 1589 6221 Io 5959.916 1821.6 1.79611485 4.111E-05 539 680 1162 4550 Callisto 7179.289 2410.3 1.235774515 4.357E-06 888 1119 1914 7492 Enceladus 7.2027 252.1 0.113331239 5.307E-05 79 98.9 169 662 Chiron 0.2669036 83 0.038743446 5.918 0.8 1 1.72 6.73 OkyrhoeComparison0.0027223 of18 Different0.008402193 Hops5.918 0.3 on0.36 Small0.62 2.43 Bodies

Jump and Wait Surveyor Hop requiring less ∆V • Surveyor-like hops are Period of usually more ∆V-efficient. GM Mean Planet Gravity Rotation 1 10 100 1000 Body (km^3/s^2) Radius (km) (m/s^2) (hours) km km km km Ceres 62.63 470 0.284 9.1 0 0 0 1 • Surveyor-like hops are 67P 6.661E-07 2 1.67E-04 12.8 1 1 1 1 better on Ceres until Moon 4903 1738 1.624 655.7 0 0 0 0 ~450km. Triton 1428 1353 0.779 141.0 0 0 0 0 Phobos 7.112E-04 11 0.006 7.7 1 1 1 1 Deimos 9.850E-05 6 0.003 30.3 0 1 1 1 • Low-gravity gravity bodies Europa 3203 1561 1.315 85.2 0 0 0 0 with high rates of rotation Ganymede 9888 2631 1.428 171.7 0 0 0 0 like Phobos, Deimos, and Io 5960 1822 1.796 42.5 0 0 0 0 Centaurs are good Callisto 7179 2410 1.236 400.5 0 0 0 0 candidates for Jump and Enceladus 7.203 252 0.113 32.9 0 0 0 0 Chiron 2.669E-01 83 0.039 5.9 1 1 1 1 Wait. Okyrhoe 2.722E-03 18 0.008 5.9 1 1 1 1 https://ssd.jpl.nasa.gov/?satellitesMarch 5, 2019 13 jpl.nasa.gov https://en.wikipedia.org/wiki/List_of_gravitationally_rounded_objects_of_the_Solar_System https://nssdc.gsfc.nasa.gov/planetary/factsheet/asteroidfact.html \ NOTE: ALTITUDES,VELOCITIES AND \ \ TIMES ARE NOMINAL \

CRUISE ATTITUDE

PRERETRO MANEUVER 30 TO 40 min BEFORE TOUCHDOWN ALIGNS MAIN RETRO WITH FLIGHT PATH

MAIN RETRO START BY ALTITUDE- MARKING RADAR WHICH EJECTS FROM NOZZLE; SPACECRAFT STABILIZED BY VERNIER ENGINES AT 60-mi SLANT RANGE, 6100 mph

Conclusions MAIN RETRO BURNOUT AND EJECTION; VERNIER PROPULSION SYSTEM TAKEOVER AT 25,000 ft, 240 mph

\ I • Hopping – both propulsive and mechanicalI – can increase I I I the science return of landed missions.I I I I • Hopping technique is dictated by the propertiesI of the destination and the hop. I • Surveyor 6’s experiment holds valuable lessons for propulsive hops.

'-3 31, "3 /3 -3

NASA/JPL-9'Caltech ''3 ; ', 'rs" "I-;- -~3 TOUCHDOWN AT 10rnph ... March 5, 2019 14 jpl.nasa.gov Fig. IV-5. Terminal descent nominal events

JPL TECHNICAL REPORT 32- 1262 43 Thank you

Questions

Acknowledgment The research described in this publication was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and – Surveyor 6 mission report, 1968 Space Administration.

March 5, 2019 15 jpl.nasa.gov jpl.nasa.gov