planetary entry overview

8/8/2019 Planetary Entry Overview

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Atmospheric Entry


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Aeroassist Technology

Aeroassist systems span a wide range ofapplications in which aerodynamic forces are used

to improve or enable a mission concept thatincludes flight through a planetary atmosphere Deceleration, acceleration, improved control

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Aeroassist Technology Applications

Entry (Landers) Entry into a planetary atmosphere from hyperbolic

approach or planetary orbit

Aerobraking (Orbiters) Used after orbit insertion to trim science orbit

Multiple passes through the high atmosphere Performed at sufficiently low density to eliminateheatshield

Aerocapture (Orbiters) Decelerates from hyperbolic approach to orbital velocity in

a single pass

Orbit control by aerodynamic lift/drag modulation

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Direct Entry

Direct entry is flight into the planetsatmosphere from hyperbolic approach ororbit. The entry vehicle can be passive

(ballistic) or actively controlled. Thepassive vehicle is guided prior toatmospheric entry and proceeds into theplanets atmosphere as dictated by the

vehicle shape and the atmosphere. Anactively controlled direct entry vehiclemay maneuver autonomously while in theatmosphere to improve landed location,

or modify the flight environment.

Successfully performed on Viking, Apollo,Shuttle, Pioneer-Venus, Galileo, Mars

Pathfinder and MER

MER Entry System

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Aerobraking Systems

Aerobraking employs atmospheric drag to reduce orbit energy (apoapsis) inrepeated passes through the upper atmosphere (near periapsis). Originally demonstrated by Atmospheric Explorer-C (Earth) and later by Magellan (Venus).

Significantly reduces the necessary propellant for orbit insertion, thus allowing areduction in launch mass and potential launch cost savings.

The primary drag surface for aerobraking is typically the orbiter solar panel(s). Maximum allowable heat rate is constrained by solar panel thermal limitations (Example:

Odyssey not-to-exceed temperature on the solar panel was 175C, which translated to amax heating rate of about 0.6 W/cm2 during aerobraking main phase).

Atmospheric density uncertainty is a major risk factor. At Mars, heat rate margins of 100% are used to accommodate large orbit-to-orbit density

variations. Despite advancements in aerobraking automation, aerobraking remains a human-

intensive process.

24 hr/day operations for weeks or months Up to 4 sequence uploads per day Detailed interaction between navigation, spacecraft team, sequencing, atmosphere

advisory group, and mission management.

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Rate DampThrough drag pass onLoose Deadbands

5 minuteGuardband

Accel Bias Calc@ Drag start 30 min

TelemetryPlayback (2)

RWAs to Tach Profile Free Desat

Start PTEPower 2ndary Gimbals

Transition to Thruster Control

Reconfigure TelecomLGA, Carrier only

@ Drag start 15 min

Slew to Drag Attitude@ Drag start 10 min

5 minuteGuardband

Stop PTETurn Off 2ndary Gimbals

Back to RWA ControlSlew to Vacuum Attitude

Back to Earthpoint@ Drag End + 10 min

Reconfigure Telecom back to HGAAccel Bias Calc

TelemetryPlayback (3)

Telemetry

Playback (1)

Drag Pass Overview


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Aerocapture

Aerocapture is a maneuver designed to take advantage of a planetsatmosphere to slow a spacecraft to orbital capture velocities and resultsin a substantial propellant reduction. This mass savings generallytranslates into smaller launch vehicles.

The maneuver begins with a shallow approach angle to the planet. Anautonomous guidance and control system modulates the vehiclesaerodynamics to mitigate off-nominal atmospheric conditions. Descentinto the relatively dense atmosphere causes sufficient deceleration and

heating to require a heatshield.

Upon atmospheric exit, the heat shield is jettisoned and a propulsivemaneuver is performed to raise the periapsis. The entire operation isshort-lived and requires the spacecraft to operate autonomously while inthe planets atmosphere.

Demands placed on the vehicle depend greatly on the specifics of theplanet being approached and the mission. Key variables include

atmospheric properties, desired orbit insertion geometry, interplanetaryapproach accuracy, entry velocity, and vehicle geometry.

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Aerocapture Benefits

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All values are compared to the mass of an all-

propulsive capture. EquivalentV fromAerocapture noted above each column.

All values are compared to the mass of an all-

propulsive capture. EquivalentV fromAerocapture noted above each column.

For delivery into 300 x 300 kmVenus orbit on same launchvehicle, aerocapture delivers

1.8x more mass into orbitthan aerobraking 6.2x more mass into orbit

than chemical only

For delivery into 300 x 300 kmVenus orbit on same launchvehicle, aerocapture delivers

1.8x more mass into orbitthan aerobraking

6.2x more mass into orbitthan chemical only

300 x 300 km300 x 300 km

1165 kg Launch Vehicle Capability

Delta 2925H-10 C3 = 8.3

1165 kg Launch Vehicle Capability

Delta 2925H-10 C3 = 8.3

Various DestinationsVarious Destinations VenusVenus

Aerocapture Chemical withAerobraking

300 x 23000 km

Chemical withAerobraking

300 x 23000 km

Chemical Only300 x 300 km




800

700

600

500

400

300

200

100

0

800

700

600

500

400

300

200

100

0DeliveredMass

inVenusOrbitCapa

bility(kg)

DeliveredMass

inVenusOrbitCapa

bility(kg)

0%

20%

40%

60%

80%

100%

Mars

Sample

Return

Mars

Micro-

orbiter

Titan Venus Saturn Neptune

%AerocaptureMassS

2.5 km/s

4.0 km/s

7.0 km/s

5.0 km/s

8.0 km/s

3.0 km/s

The Value of Aerocapture and Other Technology


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The Value of Aerocapture and Other TechnologyInvestments for Human Mars Exploration

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

Mass

SavingsNorma

lizedtoISSMa

ss

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Advanced Propulsion

Closed Loop Life Support

Advanced Materials

Maintenance & Spares

Advanced Avionics

Aerocapture

All Propulsive Chemical

Today

NOTES:

Results are cumulative and thus trends will be different

for different technology combinations/sequences

The change between points shows the relative mass

savings for that particular technology

2018 One-Year Round-Trip Mission, Crew of 4,Lander pre-deployed

Courtesy K. Joosten, Johnson Space Center

A t Al E bl Sh t


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Aerocapture Also Enables ShorterTransit TimesFor 200-Kg Arrival Mass at Neptune

0

50

100

150

200

4567891011

Use

fulInserted

M

ass(kg)

Trip Time to Neptune (Years)

Target

Aerocapture

Propulsion

Non-Deceleration System Mass into Orbit

*Courtesy of Paul Wercinski, NASA Ames Research Center

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Aeroassist Mission Summary


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Aeroassist Mission Summary

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Mission Type Launch Aeroassist Comment

Apollo E 65-69 65-69

76

78

81-pres

95

9797-98

01

04

Cassini Huygens Probe E 97 04

06

04

05

07

Active control; Aerocapture logic

Viking Landers E 75 Entry from orbit with active control

Pioneer-Venus Probes E 78

Space Shuttle E 81-pres Landing and crossrangerequirements drove geometry

Magellan AB AB performed after science mission

Mars Global Surveyor AB 96 Success despite damaged array

MRO AB 05

Mars Odyssey AB* 01 *Originally planed as AC

Galileo Probe E 89 Highest entry of all time; 60 km/s

Mars Pathfinder E 96 First direct EDL

Mars Exploration

Rovers

E 03 Much improved EDL reliability and

landed mass ratio

Stardust E 99 Highest speed Earth entry;12.8 km/s

Genesis E 01

Phoenix Mars Lander E 07 Active control planned


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Key Technologies

Approach Navigation

Thermal Protection System Deployable Systems

Atmospheric GN&C Terminal Descent System

Landing Systems

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Classic Planetar Entr References


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Classic Planetary Entry ReferencesTextbooks Vinh, Busemann and Culp, Hypersonic and Planetary Entry Flight

Mechanics, 2nd edition, University of Michigan Press, 1980. Anderson, John D., Hypersonic and High Temperature Gas Dynamics,

McGraw-Hill Book Company, 1989. Martin, J.J., Atmospheric Entry, Prentice-Hall, 1966.

Loh, W.H.T., Re-entry and Planetary Entry Physics and Technology,Volume I and II, Springer-Verlag, 1969. Regan, Reentry Vehicle Aerodynamics, AIAA Education Series, 1984.Overview Walberg, G.D., A Survey of Aeroassisted Orbit Transfer, Journal of

Spacecraft and Rockets, Vol. 22, No. 1, Jan-Feb 1985.Aerodynamics and Heating Fay, J.A., and Riddell, F.R., Theory of Stagnation-Point Heat Transfer in

Dissociated Air, Journal of Aeronautical Science, Feb 1958. Allen, H.J., Seiff, A., and Winovich, W., Aerodynamic Heating of Conical

Entry Vehicles at Speeds in Excess of Earth Parabolic Speed, NASA TR R-185, Dec 1963. Marvin, J.G. and Deiwert, G.S., Convective Heat Transfer in Planetary

Gases, NASA TR R-224, July 1965. Tauber, M.E., and Wakefield, R.M., Heating Environment and Protection

during Jupiter Entry, AIAA Journal of Spacecraft & Rockets, Vol. 8, No. 6,June 1971.

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Cl i Pl t E t R f


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Classic Planetary Entry ReferencesFlight Mechanics

Allen, H.J. and Eggers, A.J., A Study of the Motion and Aerodynamic Heating ofMissiles Entering the Earths Atmosphere at Supersonic Speeds, NACA TN-4047,1957.

Chapman, D.R., An Approximate Analytical Method for Studying Entry intoPlanetary Atmospheres, NASA TR R-111, 1959.

Chapman, D.R., An Analysis if the Corridor and Guidance Requirements forSupercircular Entry into Planetary Atmsopheres, NASA TR R-55, 1960. Citron, S.J., and Meir, T.C., An Analytic Solution for Entry into Planetary

Atmospheres, AIAA Journal, March 1965, pp. 470-475. Loh, W.H.T., Extension of 2nd Order Theory of Entry Mechanics to Oscillatory Entry

Solutions, AIAA Journal, Sept. 1965, pp. 1688-1697.

Apollo/Shuttle Curry, D.M., and Stephens, E.W., Apollo Ablator Thermal Performance at

Superorbital Entry Velocities, NASA TN D-5969, Sept. 1970. Lee, D.B. and Goodrich W.D., The Aerothermodynamic Environment of the Apollo

Command Module during Superorbital Entry, NASA TN D-6792, Apr 1972. Graves, C.A., and Harpold, J.C.; Apollo Experience Report: Mission Planning for

Apollo Reentry, NASA TN-D-6725, March 1972.

Harpold, J.C., and Graves, C.A.; Shuttle Entry Guidance, NASA TM-79949, 1979.

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