Miniaturization of Planetary Atmospheric Probes

Tony ColapreteNASA Ames

History of atmospheric entry probes and scienceWhat probes have flownWhat have they measuredWhat were their limitations

Building an entry probeSurvival First, Measure LaterTechnological (and Physical) Limitations

Changing the paradigmThe curse of Galileo - Hand-me-down scienceEnabling Sensors & TechnologyPico probes - New Architectures and Systems

“Outline”

Credits: Gary A. Allen, Jr., William H. Ailor, James O. Arnold, Vinod B. Kapoor, Daniel J. Rasky, Ethiraj Venkatapathy

History of planetary entry “probes”

Since the 1960’s:Mercury,Gemini, Apollo, Soyuz , etc. (Earth)PAET (Earth)Pioneer Venus, Vega, Venera (Venus)Viking, Pathfinder, MER, DS-2 (Mars)Galileo (Jupiter)Huygens (Titan)

Future (on the books):Phoenix Lander (Mars)Mars Science Laboratory (Mars)ExoMars – ESA (Mars)

Talked about:Venus SAGETitan Aerobot/Rover

Jupiter, Saturn & Neptune

Viking (1976)

Galileo (1995 )

Pioneer-Venus (1978)

PAET (1971), An Entry Probe Experiment in the Earth’s AtmosphereM = 62 kg, Minst = 14 Kg, Rb = .914 m

Atmospheric Science: PAET, Pioneer-Venus, Viking, Galileo and Huygens

State-of-the-Art (16 years ago): Huygens

Probe specifics:• 2.7 m diameter heat shield• Total Probe mass of 349 kg• 6 instruments (49 kg or 14%)

All In-Situ Mars Atmospheric Data…

Viking 1 & 2:• Atmospheric state variables during entry (direct). • 5 minutes each

Pathfinder and MER:• Atmospheric state variables during entry (derived).• 5 minutes each

Phoenix:• Atmospheric state variables during entry (derived).• 5 minutes

In-Situ Mars Atmosphere Profiling

In All, about 25 minutes has been spent making measurements between the surface and 80 km.

And now for the rest of the data…

T (K)100 200 300 400 500 600 700 800

z (k

m)

120110100

9080706050403020100

clou

ds

?

Venus Profile Titan Profile

And now for the rest of the data…

In all, planetary entry probes have measured ~14 individual profiles

The limitations of entry science

• Up to this point it is very costly in terms of mass, and always mass = $$

• Can only afford to fly a few (if your lucky) and usually only one - Statistics of small numbers (e.g., Galileo)

• Limited lifetime – poor temporal coverage

The challenge is to change the way probes are done to overcome these limitations!

Huygen Mission Design

Payload

Range: 5%-25%

Aeroshell (TPS)

Range: 3% - 50%

Aeroshell (strcutures)

Range: 5% - 12%

Aeroshell Parachute

Range: 2% - 5%

Power/Thermal/Com

Range: 5% - 20%

Orbit Insertion (Propulsion & Fuel)

Range: 15% - 40%

Spacecraft/Bus/ Com

Entry Probe

Range: 25% - 40%

Range: 25% - 40%

Spacecraft Mass fraction

Probe mass fraction

Cassini Spacecraft Components

Atmospheric Entry Mission & Probe Design

Mission Design Considerations:• Intended Science – Where are you headed?

• Key Factors: Mass, Volume, Power, Design Complexities (risk) and Cost

• Science payload (mass, power, etc) significantly impact both mission architecture and hardware (mass, power, complexity and cost) – Drives Probe Size

Galileo – A flight through a nuclear blast

About 50% of the probe was TPS

Jovian Entry TPS Study• Calculations by Dr. G. Allen / M. Tauber, ELORET based on Engineering Code by Tauber, et. al.

• Galileo entry conditions 48 Km/sec, - 6.64o E. angle, equatorial entry

• Carbon Phenolic TPS - TPS mass fraction is insensitive to entry probe size

• Science mass available for microprobe approx. 1 kg

Galileo: Probe Mass: 338 kg, Science Mass: 8.3% of Entry Probe massBase Radius: 1.28 m

microprobe

0.480

0.485

0.490

0.495

0.500

0.505

0.510

0.515

0

50

100

150

200

250

300

350

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Mas

s TP

S/M

ass e

ntr

y En

try mass (kg

)

Ballistic co

efficient, (kg

/m2)

Rbase

/Rbase(Galileo)

TPS mass fraction

Entry mass

Designing for Hell

The gas giants present extreme performance limits to TPS

Pascal Sample Network Configuration

Pascal – A Mars Network Mission Using Micro Probes

Pascal Probe Deployment Sequence

Pascal – A Mars Network Mission

Probe Entry System

0.5 m

Science Station

- 70° half angle cone- Hemispherical backshell- 20 kg entry mass - RHU powered

Pascal – A Mars Network Mission

Pascal Carrier S/C accommodates 24 Probes with a Delta III or IV Launch Vehicle

Stowed in D3940 Fairing

Fixed Solar Array

ADCS and Telecom Components

Power and C&DH Components

Hydrazine Thrusters

MGA’s and LGASpacecraft

Bus

Probe Dispenser Panels (4)

Pascal EDL SequencePascal EDL SequenceSelforientationSelforientation

Aft domeseparatesAft domeseparates

Parachute deployment separates

entry probe from science package

Q = 700 PaM = 1.5 – 2.2

Parachute deployment separates

entry probe from science package

Q = 700 PaM = 1.5 – 2.2

Jettison airbag andinitiate landed operations

Jettison airbag andinitiate landed operations

Airbag protects science station at impact – numerous bounces

Airbag protects science station at impact – numerous bounces

Airbag inflates immediately after chute deployment

Airbag inflates immediately after chute deployment

Entry•Speed = 6 km/s•Landing in 4 minutes

Entry•Speed = 6 km/s•Landing in 4 minutes

Chute separates after first impactChute separates after first impact

Pascal – A Mars Network Mission

Pascal requires several enabling technologies/developments

LandingSphere

Sensor Booms

Wind

Temperature

Pressure

Accelerometers

Gyroscopes

Enabling Sensors - Venus SAGE

IMU & Moutherboard

Provides information on all atmospheric state variables, stability, and winds during descent and landing.

Atmospheric Structure Investigation

2.54 cm

GSFC

1/ 2 mm.

GSFC Research thrust: one kg/one Wmass spectrograph with capability of

Cassini/Huygens technology 17 kg/ 15W

GSFC developmental time offlight mass spectrograph core 50 gm, 10 cm length

Jamieson & P. Roman/GS FC; L. Delizet,/ARC

Cassini/Huygens ion sourceThermionic electron gun

CNT based ion source undergoing evaluation

2.54 cm

GSFC

1/ 2 mm.

GSFC Research thrust: one kg/one Wmass spectrograph with capability of

Cassini/Huygens technology 17 kg/ 15W

GSFC developmental time offlight mass spectrograph core 50 gm, 10 cm length

Jamieson & P. Roman/GS FC; L. Delizet,/ARC

Cassini/Huygens ion sourceThermionic electron gun

CNT based ion source undergoing evaluation

Enabling Sensors - Amazing Shrinking Sensors

A miniaturized mass spectrometer

Modular reentry probe:• Conduct flight-testing of an integrated entry system• Flight qualification of subsystems such as TPS, innovative sensors and science instruments• Perform low cost atmospheric science experiments

Specifications:• ~ 20 cm in diameter• Total mass ~ 1 kg• Payload mass ~ 0.3 kg• Heatshield mass fraction < 7% (for Mars entry)

The Pico Reentry Probe (PREP)

Possible mission architectures

Multiple atmospheric sounders• More valuable in atmospheres where remote sensing is difficult (e.g., thick or opaque)• …or for measurements that are difficult to make with remote sensing (e.g., methane on Mars, water in Jupiter)• “Ground” truth for remote sensing (e.g., winds, composition, state)

Landed Network• Hard landers would retain the most simplicity• Synoptic weather• Seismic networks• Penetrator (e.g., DS-2)

Crewed Descent• Forward observers to high-value descent vehicles

Science instrument design•Multiple integrated sensors

TPS• Rethink design• New materials for outer planets

Terminal descent & landing• Parachute?• Heat shield separation• Novel Shapes?

Thermal and power management• Extreme operational ranges

Data storage, processing, relay & comm.• Miniature & ruggedized transmitters

Micro Probe System Considerations

Micro Probe System Considerations

3corner micro-satST5 micro-sat

Examples of integrated micro-systems

“A personal impression is that more can and ought to be done with simple sensors : a shift of emphasis from exquisite construction to testing and analysis.” – Ralph Lorentz

Concluding Thought

NASA V-Team Descent Probe• 4 accelerometers• 3-axis gyro• 2 external temperature• 2 external pressure• GPS• Total mass ~3kg

Existence Proof – NASA V-Team

The probe is no longer a vehicle but rather an instrument

into itself.