# Presentation: 183790

## VII. Aerocapture System Technologyfor Planetary Missions

- Washington, D.C.
- February 2003

**VII. Aerocapture System Technology****for Planetary Missions**

**Session Facilitator:**
**Michelle Munk**

## Outline

**Executive Summary**
**Aerocapture Capabilities to be Validated by ST9**
**Aerocapture Overview**
**Aerocapture as an Enabling Technology**
**Technology Areas to be Addressed by ST9**
**Experiment Requirements**
**Science Capabilities Roadmap**
**Aerocapture Mission Summary**
**Technology Roadmap**
**State of the Art**
**Figures of Merit Definitions**

## Executive Summary

**The Splinter Sessions Focused on the Following Technology Areas**
**System and Performance Modeling**
**Aerodynamics and Aerothermodynamics**
**Thermal Protection Systems/Structure**
**Guidance, Navigation, and Control (GN&C)**
**Session Topics**
**Future space science mission needs**
**Desired workshop products**
**Technology splinter session discussions**
**Needs/potential capabilities assessments**

## Executive Summary (continued)

**Key Observations**
**Aerocapture is applicable to all planetary destinations with suitable atmospheres (Venus, Earth, Mars, Jupiter, Saturn, Titan, Uranus, and Neptune)**
**The primary advantage of aerocapture is propellant mass savings. The net vehicle mass savings range from 20-80% depending on the destination and can manifest themselves in terms of smaller, cheaper launch vehicles or increased payloads.  **
- Preliminary results indicate that some missions (e.g. Neptune Orbiter) cannot be done without aerocapture because they won't fit on the largest available launch vehicle (Delta IV heavy).
- Aerocapture can also reduce trip time (by allowing higher arrival speeds than chemical capture can feasibly accommodate), and enable new missions with increased flexibility
**Aerocapture is a systems technology in which most of the elements already exist due to development in other aeroentry applications. The critical next step is to assemble these elements into a prototype vehicle, fly it in the space environment and thereby validate the design, simulation and systems engineering tools and processes**
- This need is very well matched to the NMP program objective that ST-9 be a systems level validation experiment
**ST-9 flight experiment is key to making aerocapture technology available to science missions**

## Executive Summary (continued)

**Recommendations for ST-9 Flight Experiment**
**ST-9 should validate the most mature and immediately useful vehicle configuration, which is the blunt body aeroshell**
- Blunt body aeroshell systems provide robust performance for aerocapture at all “small body” destinations in the solar system (Mars, Titan, Venus, Earth)
- The validation will be directly relevant to other aeroshell geometries (as will be needed for the gas giants) for the guidance, simulation and systems engineering disciplines
**The ST-9 flight validation must demonstrate a drag delta-V of 2 km/s, in order to involve all of the essential physics of the problem and serve as an acceptable validation of aerocapture**
- Although the ST-9 cost cap precludes a "true" aerocapture flight test involving a hyperbolic to elliptic orbit change effected by atmospheric drag, this objective can be accomplished with an elliptical-to-elliptical orbit change.
**The ST-9 flight test should include an autonomous periapse raise maneuver after the atmospheric portion of the flight**
**The ST-9 vehicle should incorporate diagnostic instrumentation to the maximum extent possible under the cost cap**
- The two priorities are to get information about the hypersonic flow field around the vehicle and to quantify the performance of the thermal protection material.
**The ST-9 vehicle should baseline mature TPS and structural materials to minimize risk**
- However, it is recommended (if affordable given the cost cap) that the vehicle incorporate a test coupon of one or more new TPS materials that are candidates for future aerocapture and/or aeroentry missions at other planets. These coupons should be incorporated in such a way that their failure does not compromise the overall flight test experiment

## Aerocapture Capabilities to be Validated by ST9

|  | Figures of Merit |  |  |  |  |
| --- | --- | --- | --- | --- | --- |
| Required Capability | Now
 | ST9
 | SSE Ultimate
 | Current TRL | TRL 5 Test Requirement |
| Aftbody aeroheating uncertainty (%) | 200 | 100 | 100 | N/A | N/A |
| Aero/RCS interaction uncertainty (%) | 300 | 100 | 100 | N/A | N/A |
| Aerocapture GN&C validated | Validated by simulation | Validated by flight | Provided by ST9 | 5 | 7 |
| GN&C validation (# of segments flight validated) | 2 | 3
Mission critical exit phase validated | 3
Provided by ST9 | N/A | N/A |
| Atmospheric flight simulation validation for aerocapture | Monte Carlo trajectories predicted for range of environments, uncertainties | Trajectory reconstruction validates predicted trajectory, flight environment, uncertainty | Provided by ST9 | 5 | 7 |
| Vehicle captured into required orbit, aeromaneuvering effort indicator within 3-Sigma range predicted | Success predicted by simulation, 3-sigma aeromaneuvering effort indicator predicted through Monte Carlo | Success validated by flight, aeromaneuvering effort indicator within 3-sigma range predicted | Provided by ST9 | 5 | 7 |
| Vehicle completed autonomous periapsis raise maneuver, Delta V for periapsis raise within 3-Sigma range predicted | Success predicted by simulation, 3-sigma Delta V predicted through Monte Carlo | Success validated by flight, Delta V within 3-Sigma range predicted | Provided by ST9 | 5 | 7 |
| Aerocapture spacecraft/aeroshell integration validated | Success predicted by design methods | Success, design methods validated by flight | Provided by ST9 and design work for SSE | 5 | 6 |

## Aerocapture Overview

- Aerocapture is an orbit insertion flight maneuver executed upon arrival at a planet.
- Spacecraft flies through the atmosphere and uses drag to effect multi-km/s deceleration in one pass
- Requires minimal propellant for attitude control and a post-aerocapture periapse raise maneuver.
**Benefits**
- Significant reduction in propellant load; arrival mass can be reduced by 20-80% for the same payload mass depending on the mission
- Achieves the required orbit faster than with aerobraking or SEP alternatives (hours vs weeks/months)
- Can result in reduced flight times since arrival speeds can be higher than for propulsive capture
**State of the Art**
- Never been attempted before
- Considerable relevant experience from past aeroentry and aerobraking missions
- Sufficient technical maturity exists for a flight test experiment

*Hyperbolic *
*approach *
*trajectory*

*Aerocapture maneuver*

*Periapse *
*raise *
*maneuver*

* **Low L/D aeroshell*

**Primary Technical Approach**
- Spacecraft carried inside a protective aeroshell
- Aeroshell provides both thermal protection and aerodynamic surface functionality
- Aeroshell cutouts and feedthroughs enable full spacecraft functionality during cruise
- Automatic guided flight through atmosphere using specialized algorithms/software
- Aeroshell jettisoned after capture

**Aerocapture Overview**

## Aerocapture is an Enabling Technology

**Aerocapture can save so much propellant mass that it enables missions that cannot otherwise be done**
**Propulsive orbit insertion obeys the rocket equation: M****fuel**** ~ exp(********V)**
**Aerocapture mass is predicted to scale almost linearly:  M****AC**** ~ ********V**

## Aerocapture Technology Areas to be Addressed by ST-9

**Complete systems level test of a free-flying vehicle in order to validate the design, simulation, and systems engineering tools and processes. **
**This validation will directly address flight mechanics, vehicle design, systems engineering and integration, no matter what the future planetary destination is. **
**This validation will partially address aerothermodynamics and TPS, since the applicability to future missions is more limited because of the specialized needs of the different destinations.**

## Experiment Requirements

**In a single atmospheric pass, utilize bank angle modulation through an atmosphere to remove the necessary amount of delta V from the vehicle approach trajectory to achieve the target orbit.**
- The delta V achieved during this maneuver must be on the order of 2 km/s  to validate all phases of the guidance and achieve hypersonic continuum aerodynamics
**Validate a mature and immediately useful vehicle configuration**
**Perform an autonomous periapse raise maneuver after the atmospheric portion of the flight**
**Utilize diagnostic instrumentation to the maximum extent possible, to acquire information about the hypersonic flow field and quantify the performance of the thermal protection material.**
- The information obtained will be the key to model validation and technology infusion

## ST-9 Feed-Forward to Science Capabilities

** **

- ST9
- Space
- Validation

- SOA

- Time

- Capability

- Small
- Planets
- And
- Moons

- Gas
- Giants

- Ground
- Development/
- Testing

- Blunt Body Aeroshells
- L/D  .25

- Slender Body Aeroshells
- L/D  .25

## Aerocapture Mission Summary

**Ref: Jeffrey L. Hall, Muriel Noca, JPL**

## Aerocapture Technology Development Roadmap

**LMA – Aeroshell – 800-52-06**

**Aerocapture Technology Development Roadmap**

**Competed - Cycle 1 NRA **

**2003**

**2004**

**2005**

**ATP**

**2006**

_***Option 1***_

_***Base***_

- Aerocapture Roadmap 012703.ppt

_***Option 2***_

**ATP**

**ATP**

**ATP**

**ATP**

**Ball – Ballute – 800-52-03**

- C-CSpecimen Tests

- C-C TPS Tests

- “Warm” Struc Coupon Tests

- “Warm” Struc Component Test

- “Warm” Structures Prototype

- Titan Screening

- Titan TPS Downselect

- Titan TPS Characterization Test

- SolarTower Test

- Arcjet Test 1

- Arcjet Test 2

- Neptune TPS Downselect

- Turbulence
- Model for Mid L/D

- Heat Flux & Recession Sensor Req’mts

- Detailed Drawings

- Sensor Fab

- Lab Tests Complete

- Sensor &Plug Designs

**ATP**

- Materials Coupon Results

- Feasibility Assessment

- Baseline Concept

- Configuration Trades

- Earth Test Requirements

**2002**

**Systems Analysis**

**Mars Sample Return**

**Tool**
**Development**

**2007**

**2008**

**2009**

**2010**

**2011**

**2012**

**2013**

**ELORET – Sensors – 800-52-04**

**ARC – TPS – 800-52-01**

**ARA – Ablator – 800-52-02**

**LaRC – Structures – 800-52-05**

**Radiation Modeling Tool**
**TPS Design Tool**
**Guidance and Navigation Tool**
**Engineering Atmosphere Tool**
**Aerothermodynamic Modeling **
**Mass Properties and Structures**
**Ballute Design Tool**
**Flight Simulator Tool**

**ST-9 Earth****Flight Validation**

**Venus?**

**Mars Science Laboratory**

**Mars Scout**

**Titan**

**Neptune****2012+**

**Cycle 2 NRA (2 awards planned)**

- Aftbody Attached Ballute

- Forebody Attached Ballute

- Deployment
- Test

- Insulation
- Mat’l Test

**Titan Aeroshell Aerocapture**
**Neptune Aeroshell Aerocapture**
**Aerocapture at Other Destinations**
**Aerocapture Feasibility**
**Aerocapture Benefits**
**Aerocapture Compatibility**
**Earth Demo Applicability**
**Aeroshell/Ballute Quicklook**

**Concept Studies**

**Systems Definition****Studies**

_**ATP Products:**_
**1m-2m Carbon-Carbon structural/TPS system**
**1m-2m ablative structural/TPS system**
**TPS integrated heat flux sensors**
**TPS integrated recession sensors**
**Towed ballute prototype**
**Aerocapture at Titan: Systems definition study complete **
**Aerocapture at Neptune: Systems definition study complete**
**Attached ballute(s) prototype design**
**Aerocapture at Mars: trade studies complete**
**Aerocapture at other SSE destinations: trade studies complete**
**Aerocapture flight demo proposal to New Millennium complete**
**Aerocapture Systems Analysis tools developed for Code S needs**

## State of the Art

**Aerocapture has never been flown in space**
**Elements of aerocapture have been flown**
**Aeromaneuvering (lifting, guided and controlled) with low L/D aeroshell, lift vector modulation with low control authority**
- Apollo, Gemini
**Atmospheric exit human rated for Apollo, but never flown**
**Russian Zond 6 spacecraft performed loft on Lunar return, to reach U.S.S.R. in 1968 (using pre-programmed bank commands)**
**Aeroassist demonstrated spacecraft with similar characteristics**
- Viking – lifting, controlled, unguided Mars Entry, Descent and Landing
**Ballistic entries completed at**
- Mars, Jupiter, Venus, Earth, Titan (Huygens Jan 05)
**Shuttle**
**Trailing ballute never flown**
**Russians built, launched, attempted re-entry of inflatable ballistic attached ballute**

## Figure of Merit (FOM) Definitions

- Lift-to-Drag Ratio (L/D) - an aerodynamic term which quantifies the relative amounts force, perpendicular to the relative wind that constitutes an upward force (lift), and parallel and opposite the direction of motion (drag).  In practical terms, this is a measure of the controllability of a vehicle.  A ballistic vehicle has a lift-to-drag ratio of zero; a slender, winged vehicle has an L/D of greater than 1.  For aerocapture, a vehicle with a higher L/D can maneuver through a more narrow flight corridor and compensate for greater uncertainties, but will be aerodynamically more complex than the high-heritage blunt body.