Small Satellite Aerocapture for Increased Mass Delivered to Venus and Beyond

Home , Aerocapture, Thrusters (spacecraft)

Adam Nelessen / Alex Austin / Joshua Ravich / Bill Strauss NASA Jet Propulsion Laboratory Ethiraj Venkatapathy / Robin Beck / Paul Wercinski / Mike Wilder / Gary Allen / Michael Aftomis NASA Ames Research Center Robert Braun / Michael Werner / Evan Roelke University of Colorado Boulder June 14, 2018 © 2018. All rights reserved. Overview

• A multi-organizational team is developing an aerocapture system for Small Satellites • Currently in year 1 of a 2-year effort !2 !1 • Utilize drag modulation flight control to mitigate atmospheric & navigation uncertainties • Initially studied by Putnam and Braun in “Drag Modulation Flight Control System Options for Altitude Planetary Aerocapture” (km) • Simplest form is the single event jettison • Ballistic coefficient ratio (β2⁄β1) provides control authority

• Study addresses key tall tent pole challenges Deceleration 1. Orbit targeting accuracy (g) 2. Thermal protection system feasibility 3. Stability before, during, and after jettison event

• Technology development has so far been Heat Rate “mission-agnostic” (W/cm2) • Pursue a notional flight system design and target orbit to demonstrate existence proof • Design and tools can be custom-tailored for a range of possible science missions Planet-Relative Velocity (km/s)

6/14/18 2 Mission Applicability

• Potential Destinations: • Venus Mechanical deployable drag skirt • Earth • Mars • Titan • Ice Giants • Vehicle Options: • HIAD Rigid drag skirt • Mechanical deployable drag skirt • Rigid drag skirt • Delivery Schemes: • Dedicated launch & cruise • Delivery by host spacecraft

6/14/18 3 Mission Applicability

Initial Focus: Chose Venus to bound the technology’s capability. Can scale to “easier” destinations. Chose rigid drag skirt and host spacecraft delivery to minimize system complexity.

6/14/18 4 ConOps: Exo-Atmospheric

Poten8al Hosts: • Dedicated carrier spacecraA • Discovery or New FronEers missions that target or ﬂy by Venus

Atmospheric Entry Entry Velocity = 11 km/s to Atmospheric Entry Flight Path Angle ! = -5.40 deg Coast "

Deploy from host S/C

6/14/18 ConOps: Atmospheric

Atmospheric Flight Nominal Peak Heat Rate: 383 W/cm2 Nominal Peak Deceleration: 9 G Atmospheric Entry Drag Skirt Separation ! Entry Velocity = 11 km/s Ballistic Coefficient Ratio: 9 Flight Path Angle ! = -5.40 deg Nominal Time: Entry + 93 sec Nominal Velocity: 8.9 km/s

Atmospheric Exit Nominal Time: Entry + 270 sec Nominal Velocity: 7.75 km/s

6/14/18 ConOps: Post-Aerocapture

Initial Orbit Periapsis: 100 km Apoapsis: 2000 km Period: 1.83 hr

Drop Heat Shield + Periapsis Raise Maneuver Nominal Time: Atm. Exit + ½ Period Trigger: Timer

6/14/18 ConOps: Post-Aerocapture

Initial Orbit Final Orbit Periapsis: 100 km Periapsis: 200 km Apoapsis: 2000 km Apoapsis: 2000 km Period: 1.83 hr Period: 1.85 hr

Drop Heat Shield + Periapsis Raise Maneuver Nominal Time: Atm. Exit + ½ Period Trigger: Timer

6/14/18 Representative Flight System

Pre-Je&son Conﬁgura0on Delivered Flight System

Rn= 10 cm 40 cm 150 cm

!Ra#o = 9 Total Margined Mass = 69kg • Science Payload • Thermal • ~1.5U available volume • Kapton Film Heaters • Tel ecom (~2.5 kbps to 70m DSN) • MLI • IRIS X-Band Radio • Power (~25 W with body mounted solar cells) • X-Band Patch Antenna • Solar Arrays • X-Band Circular Patch Array HGA • Clyde Space EPS • ACS (~10 arcsec pointing accuracy) • 18650 Li-ion batteries (x11) (~180 Wh) • BCT Star Tracker, Sun Sensors (x4), and Control • Propulsion (~70 m/s delta-V) Electronics • 0.5 N Monoprop Thrusters (x4) • BCT Reaction Wheels (x3) • Mechanical • Sensonor IMU • Structure, TPS, Rails, Rollers, Separation • C&DH Hardware • JPL Sphinx Board • Pyro Control Board

6/14/18 9 Orbit Delivery Accuracy

• 3DOF Monte Carlo runs in trajectory tool used to assess orbit targeting accuracy • VenusGRAM atmospheric model with 3-sigma variability in density and wind speeds

• Options for improving orbit targeting accuracy are under investigation • Reduce EFPA error • Increase ballistic coefficient ratio • Improve G&C algorithm for drag skirt separation timing

6/14/18 10 Mass Efficiency Comparison

Mass Efficiency Comparison

Delivered Mass Orbit Insertion Mass 80

50 35 42 40 46 51 48 40 55 53 Mass [kg] 30

20 33 26 28 22 10 17 20 14 15

0 Aerocapture Propulsive, Propulsive, Propulsive, Propulsive, Propulsive, Propulsive, Propulsive, System, 2000km 3000km 5000km 7500km 10000km 20000km 35000km 2000km Target Orbit Apoapsis Altitude [km]

• The aerocapture-based orbit insertion system delivers 85% more useful mass to a 2000km apoapsis orbit than an all-propulsive system

6/14/18 11 Other Activities

NASA Ames Stagnation Point Heating vs Time • Aerothermal analysis • TPS sizing • CFD simulations

3 • Ballistic range test Shot 2798: P¥ = 114 Torr (0.15 atm), r¥ = 0.181 kg/m development See Robin Beck’s presentation “Studies in support of Venus 3 aerocapture utilizing drag Shot 2799: P¥ = 76 Torr (0.1 atm), r¥ = 0.121 kg/m modulation” for more information

3 CU Boulder Shot 2800: P¥ = 50 Torr (0.067 atm), r¥ = 0.079 kg/m • G&C algorithm development

• CFD simulations 1 m 2 m 3 m 4 m* 10.13 m from Muzzle See Michael Werner’s presentation “Dynamic propagation of discrete- event drag modulation for Venus aerocapture” for more information

6/14/18 12 Conclusions and Future Work

This initiative addresses the following key challenges for drag modulation aerocapture at Venus: 1. Orbit targeting accuracy • 3DOF Monte Carlo simulations of the maneuver • G&C algorithm improvements (Work to Go) 2. Thermal protection systems • Preliminary aerothermal assessment and TPS design • CFD detailed aerothermal assessment (In Progress) 3. Stability before, during, and after jettison event • Preliminary 6 degree-of-freedom simulations • CFD analysis of dynamics of drag skirt separation (In Progress) • CFD aerodynamic database generation (Work to Go) • Ballistic range testing (Work to Go) • To improve mission accommodation options, investigating an ADEPT-based mechanical deployable drag skirt option 6DOF Trajectory Simulation CFD Separa=on Analysis Ballistic Range Model Design

6/14/18 13 Thank you!

6/14/18 14 Internal Flight System Configuration

Payload Volume 3 (10 cm shown) Pyro Control

Star Tracker IMU

Patch Antenna EPS Board

Reaction Avionics Stack Wheel (x3) (Computer, Radio, Separation ACS Electronics) Rollers (x3) Backshell

Circular Patch Antenna Array

Thrusters (x4)

Batteries Propulsion (x11) Tank Heatshield Structure Ballast Mass TPS 6/22/18 15