The Mars Gravity Biosatellite Program

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The Mars Gravity Biosatellite Program

• Charity Lewis
• Space Systems Design Lab Undergraduate Researcher

The Mars Society at Georgia Tech April 10, 2007
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Overview

• Science Objectives
• Mission Architecture
• Entry, Descent, and Landing Overview
• Trajectory Analysis
• Conclusions

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Mission Overview
To investigate the effects of Martian gravity on
mammals

• Biosatellite will house 15 mice in low
  Earth orbit for five weeks
• Satellite will be spun at 32 rpm to
  simulate the 0.38g environment of Mars
• Reentry with rapid air-based recovery
  for post-flight analysis
• Total mission cost estimated to be 40 million
• First prolonged investigation of mammalian
  adaptation to partial gravity

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Scientific Objectives

• In a suitable mammalian model, quantify the
  extent of the following effects as a result of
  extended exposure Mars-equivalent levels of
  artificial gravity on the following (as compared
  to both microgravity and 1-g physiology, wherever
  possible)
• Bone loss
• Muscular atrophy
• Neurovestibular adaptation
• Immunology radiation effects

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Bone Mineral Density
6 months _at_ -1.5 / month
18 months _at_ unknown rate
6 months_at_ -1.5 / month
(Looker, 1998 De Laet et al., 1997 Hoffman
Kaplan, 1997, Cummings et al, 2002)
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Mission Profile
Deployment and Transition
Deorbit
Orbital experiment, 5 weeks
Launch
Entry, Descent, and Landing
Recovery and Analysis
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University Partners
MIT
Georgia Tech

• Program Office
• Payload Module engineering development and
  fabrication
• Science management
• Launch Vehicle arrangements
• Bus Module engineering development and
  fabrication
• Systems Integration and testing

• Entry, Descent and Landing modeling and analysis
• Reentry Vehicle engineering development and
  fabrication
• Systems Integration

Past Major Participants
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Entry, Descent, and Landing
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Science Requirements

• Deliver specimens to science team within 2 hours
  of touchdown
• Maintain an internal temperature of less than
  37C
• Stay within specified g-load limits

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EDL Flight Phases
5 m drogue chute deployed at Mach 1.5
12 m main chute deployed at Mach 0.3 (20 km alt)
Payload recovered via helicopter (3 km alt)
Main chute slows Vehicle to 8 m/s
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Mid-air Recovery

• Advantages
• Delivers payload within requisite 2 hours
• Avoids heavy impact loads
• Significant mass savings
  over crushables
• Disadvantages
• Historically requires a
  landing footprint of lt80 km

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Trajectory Analysis

• All trajectory analysis was performed with POST
  (Program to Optimize Simulated Trajectories)
• POST provides the capability to
  target and optimize point mass
  trajectories

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POST Inputs and Outputs
Bus Mass
POST
Entry Trajectory
Entry Vehicle Mass
Entry Flight Path Angle
Orbital Elements
Heat Load
Specific Impulse
Entry Vehicle Shape
Heat Rate
Landing Target
g - Load
Deorbit ?V
Terminal Velocity
Atmospheric Density
Landing Location
Parachute Diameters
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Landing Ellipse Sensitivity Study

• If all parameters could be perfectly predicted,
  the landing ellipse would be a single point,
  however, there is an inherent amount of
  uncertainty in each of the parameters
• Each set of parameters is varied individually
  using a Monte Carlo analysis to determine the
  resulting maximum landing ellipse diameter

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Landing Ellipse Sensitivity Study
science orbit
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Best Case Landing Ellipse
(All parameters known except Cd and atmospheric
density)
80 km
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Nominal Entry Trajectory

• Peak Deceleration 12.8 g
• Peak Convective Heat Rate 121.5 W/cm2
• Integrated Convective Heat Load 10.7 kJ/cm2
• Time to touchdown 52 minutes
• Velocity at interception 8.3 m/s
• Entry flight path angle -2.9

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Decreasing Landing Ellipse

• Landing ellipse is nearly twice the estimated
  size required for mid-air recovery
• Primary method of decreasing landing ellipse will
  be by increasing entry flight path angle
• Time to touchdown will decrease
• Heating with increase
• g-load will increase

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Conclusions

• Innovative student lead mission to investigate
  the effects of Martian gravity on mammals
• Joint initiative between Georgia Tech and MIT
• Data returned will be highly useful when planning
  future manned missions to Mars
• Work to be done to decrease landing ellipse

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Available Georgia Tech Work

• Trajectory analysis
• Structures and mechanisms design
• Computer and data architecture (software)
• Systems engineering (requirements, documentation,
  integration)
• Descent and landing/recovery systems
• Thermal protection systems

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Contact Information

• Charity Lewis
• charity_at_gatech.edu
• Ashley Korzun, GT Project Manager
• akorzun3_at_mail.gatech.edu
• Program Website
• www.marsgravity.org/
• Your Name Into Space
• www.yournameintospace.org/

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