How Do You Qualify Heat Shields on Earth?

April 14, 1982

Space Shuttle Columbia STS-003

Kuiper Airborne Observatory

Infra-Red image

Or: Electric Arc Jet Testing at

NASA Ames

1998

Ames IHF arc jet facility

Ablating disk with bow shock

INITIALS-2

CSC/SETI Institute Colloquium Series

July 29, 2009

John Balboni

Thermo-Physics Facilities

NASA Ames Research Center

December 2004

Meridiani Planum

Mars Exploration Rover Opportunity

Heat shield and impact site

INITIALS-3

Heat Shield: ~10% of landed mass

820 kg (rover, lander, heatshield, parachute)

~$820,000,000 for two Mars Rovers (APPROXIMATE)

~$500,000 per kg landed mass (two rovers) (APPROXIMATE)

two Heat Shields cost ~$80,000,000 (APPROXIMATE)

Heat Shields: Impact on Science

INITIALS-4

INITIALS-5

Galileo entry probe was 45% heat shield: 150 kg “dead” wt.

Mass

Mass

Mass

Science payload

mass is inversely

proportional to

the “delivery” mass,

including the heat shield

Galileo Jupiter Probe: 1995

INITIALS-6

Columbia STS-107: April 1, 2003

Heat shield failure may lead to complete failure of the mission and loss of the spacecraft

• R&D: provide critical data for the research and development of thermal protection (TPS) materials

• Flight Qualification/Sustaining Engineering: qualify/certify TPS materials and processes for National Programs

• Instrumentation: Develop surface and in-depth instruments and sensors

• Space Ops: Support TPS damage assessment and verification of repair techniques for crewed spacecraft

Rationale for Arc Jet Testing

X-33SHARP B1 & B2 NASPPAET

VIKING

PIONEER-VENUS

GALILEO MER

MAGELLAN PHOENIXSTARDUST

MARS PATHFINDER

Orion

SPACE SHUTTLEAPOLLO

X-37FALCON/CAV

INITIALS-7

Space Shuttle

Tile Damage

INITIALS-8

Acknowledgements

Contributions and charts provided by:

Dr. Michael Wright, NASA Ames

Dr. George Raiche, NASA Ames

Dr. Bernie Laub, NASA Ames

Ernest Fretter, NASA Ames

Bonnie James, NASA Marshall Space Flight Center

INITIALS-9

Summary:

The Problem (and Solution)

The Analyses

The Experiments

The Facilities

INITIALS-10

The Problem (and Solution)

INITIALS-11

The Solution: Blunt Bodies_2

INITIALS-12

Stardust Mission: Video

(play video here)

INITIALS-13

The Root Problem: Speed

Physics dictates high speeds for space travel. Consider

circular orbits at 1.025 x Radius:

Satellite Speed Escape Speed

Mars . . . . . . . . 3.5 km/sec 5.0 km/sec

Venus . . . . . . . 7.2 km/sec 10.3 km/sec

Earth . . . . . . . . 7.8 km/sec 11.2 km/sec

Jupiter . . . . . . 41.7 km/sec 59.5 km/sec

Kinetic Energy ~ mV2

Surface Convective Heat Transfer Rate ~ V3

INITIALS-14

The Solution: Blunt Bodies

INITIALS-15

The Solution: Blunt Bodies

INITIALS-16

The Solution: Blunt Bodies

INITIALS-17

The Solution: Blunt Bodies

MSL = Mars Science Laboratory (rover); 2011 Launch

INITIALS-18

The Space Shuttle: Thermal Protection

RCG CoatingFRCI-12 Tile

Gap Fillers

AIM-22 Tile AFRSI Blanket

TUFI/AETB Tile

INITIALS-19

The Analyses

INITIALS-20

Hypersonic Flight: Analysis

INITIALS-21

Hypersonic Flight: Analysis

CFD = Computational Fluid Dynamics

INITIALS-22

Hypersonic Flight: Analysis

INITIALS-23

Hypersonic Flight: Analysis

Except for Space Shuttle, all past Earth entry vehicles and all planetary entry vehicles use “Ablative” heat shield materials.

TPS = Thermal Protection Sysetm (Heat Shield)

INITIALS-24

Ablative Heat Shield: Physics

INITIALS-25

Ablative Heat Shield: Physics

INITIALS-26

The Experiments

INITIALS-27

Arc Jet Test Objective

Verify on the ground the heat shield integrity before atmospheric entry

Develop and characterize material properties Screen candidate materials

Verify heat shield design: gaps, attachmentsDevelop and characterize instrumentation

Verify heat shield repair techniques

Example:

INITIALS-28

Arcjet Diagnostics and Analysis: Flight Traceability example

Entry vehicle shape is established,

Aerothermal analysis predicts the flight environment

Arc Jet flow analysis determines appropriate arc jet test configuration

and in-depth material response

Arc jet diagnostics measure the free-stream conditions and

material response

0.1

1

10

Heat

Flux, W

/cm

2

0.60.50.40.30.20.10.0

X, m

Calibration Data CFD

Calibration Data and Pre-Test Predictions

Comparing experimental and modeling data confirms arcjet-to-

flight correspondence

TPS is sized to the aerothermal environment; Final arc jet tests establish TPS flight certification

and 3 TIRS rockets with covers were added at a late date

MER TIRS flight article

CFD solution of TIRS cover and backshell TPS arc jet test in PTF

Photo of TIRS arc jet test in PTF

MER aeroshell

in 3D with chemically reactions in the flow and at the surface

INITIALS-29

Space Shuttle Wing Leading Edge Repair

Pre-test: 9x9 inch panel with 7’’ plug repair

15 min. arc-jet test; exceeding 2000 C on the material

INITIALS-30

The Facilities

INITIALS-31

Arc Jet Complex

STATUS: Operational (Commissioned 1962)

LOCATIONS: N-234 and N238

Four Arc-Jet Facilities: • Aerodynamic Heating Facility (20

MW)• 2-By- 9-Inch Supersonic Turbulent

Flow Duct (20 MW) • Panel Test Facility (20 MW) • Interaction Heating Facility (60 MW)

One of only three such facilities in the US;

(Two NASA, One DoD)

INITIALS-32

IR image of tile panel;Top view

Flow

Panel test in semi-elliptical

flow nozzle; side view;

80 cm x 80 cm

Arc Jet Panel Test

Arc Jet Schematic

Objective: Simulate entry heating in a ground-test facility

Goal: Verify a thermal protection material/system design before flight; support continuing engineering during operations

Method: Heat a test gas (air) to plasma temperatures by an electric arc, then accelerate into a vacuum chamber and onto a stationary test article

Vacuum Test Chamber

High Energy FlowMach 5 - 7 at exit

10-45 MJ/kg

Simulates altitudes 30–60 kmGas Temp. > 8,000 K

ARC HEATER NOZZLE TEST CHAMBER

Ames High Enthalpy Test Facilities

Panel Test Facility20 MW - TPS Panel Testing

Aerodynamic Heating Facility20 MW - TPS Free

Jet Testing

Interaction Heating Facility

60 MW - TPS Free Jet and Panel Testing

2”x9” Turbulent Flow Duct20 MW - TPS Panel Testing

INITIALS-34

Arc Jet Test Crew

Arc Jet PhotoArc Jet Test Samples

Arc Jet Walk-Around

(play video here)

Arc Jet Test

(play video here)

INITIALS-39

Future Human Exploration

INITIALS-40

Scenario: Lunar Exploration

EXAMPLE ONLY

All lunar sorties require Earth return entry vehicle:

Reference ESAS Requirements Study, June 1, 2005

INITIALS-41

Candidate CEV Configuration

Reference ESAS Requirements Study, June 1, 2005

Ames is positioning itself for a major role in TPS design

INITIALS-42

Summary - Conclusion