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LEMuRS�Lunar ElectroMagnetic Prospector Rover for Sample return��ASTE-527 Space Studio Architecting�Fall 2018 Final

MARTIN GRECO

MGRECO@USC.EDU

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WHY?

BACKGROUND AND CONTEXT

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Lunar Sample Return Background

  • Lunar samples provide a wealth of information on planetary formation as well as potential landing, settlement and mining sites

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  • The samples returned from the 6 Apollo sites are insufficient for us to understand the Lunar surface as we prepare for a return to the Moon

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  • Manned sample return missions have a few challenges associated with attaining a diverse sample return program
    • 1) Does not provide timely return of sampled materials
    • 2) Does not provide a prospecting architecture
    • 3) Does not provide an augmentation for future Lunar mining options

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  • We will look at a method to increase the number of returned samples per landed mission as well as their diversity

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Concept and Rationale

  • Develop a propellant-less sample launching rover capable of delivering multiple samples to the proposed LLO Lunar orbiting station for examination and potential transfer to earth

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  • These prospecting samples would inform on future landing sites for landers, rovers and settlements

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  • Rovers can be deployed to numerous locations on the Lunar surface allowing for a variety samples

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  • The propellant-less architecture can expand the lifetime and range of the prospecting rover

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  • The Prospecting Rover would inform the feasibility and regions for future Lunar mining operations

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Proposed architecture would be responding to NASA Exploration Campaign plan for near term goals of answering Space Policy Directive SPD 1-3

Provides a path towards developing large scale exploration

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HOW?

DESCRIPTION AND FEASIBILITY

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Concept Of Operations

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Rover Description

  • Sample Return ElectroMagnetic Gun (SREMG) Rover would provide a tele-robotic or autonomous sample return system
    • Tele-robotics and automation could extend lifetime of Gateway experiments
    • EM gun can be contracted to the commercial sector given the work being performed for the Navy by companies such as BAE and General Atomic

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  • Architecture Assumptions:
    • Impart dV > 1.73 km/s to LLO for the sample system
  • Gun Rail Specifications
    • Gun Rail Length = 3.25m
    • Gun Rail Width = 1m
    • Gun Rail Max Current = 3.3e6 A
  • Sample System
    • 32 Kg total mass
    • Holds ~20 samples with a mass of 15 Kg
    • Star5D used to circularize orbit

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SREMG Rover

Sample

System

Lunar Station

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RTG

Stabilizers

Orbit Circularization Motor

EM Gun

Sample

SS

El

Gimbal

Avionics

Batteries

Capacitor Bank

Samples

x20

Collection Arm

Antenna

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Mass Feasibility Calculations

Rover Mass

  • Assuming Curiosity Class Capability of 919 Kg

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  • Scaled up with:
    • Rail Gun : 100 Kg
    • Sample System Loader : 50 Kg
    • Augmented Systems:
      • Avionics
      • Harness
      • Mechanical

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  • LEMuRS Rover Mass of 1630 Kg
    • For comparison Apollo LM “truck” concept could have delivered ~5000 Kg payload and Surveyor landers delivered ~1000 Kg

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Simplified Equations

Ignores, friction, thermal, etc..

EMG Electrical System

  • Capacitor Bank
    • Operating Voltage = 250 V
      • Cap part no : Maxwell BCAP2000 P270 K04
        • Capacitance = 2000 F
        • Cell Voltage = 2.7 V
        • Series strings = 56
        • Parallel strings = 11
        • Total Cap = 616
    • Mass* = 222 Kg
    • Volume* = 287e3 cm^3

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*includes packaging overhead

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Railgun vs Coilgun

  • While the coil gun design is more complicated electrically and not as efficient when compared to a rail gun there are some advantages that should be explored

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  • Sample system would levitate on gun rail
    • No need for an armature
    • No thermal or erosion effects
    • No energy loss to friction results in higher velocity

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  • Acceleration profile is tunable
    • Limiting sample system g’s
    • Limiting force on lander

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Sample Launch ConOps

1. Launch Location

4. Circularization Burn

2. Sample Spun for Stability on Coil Gun

3. Sample Launch

5. EP Chaser Orbit Match and Capture

6. EP Delivery to LLO Station

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FUTURE STUDIES AND SUMMARY

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Future Work (1)

  • 1) Calculate Launch Mass for Lander and Rover egress system

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  • 2) Refine Landing and Egress System

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  • 3) Increase understanding of Launcher Errors
    • For sample system stability and orbit injection

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  • 4) Augment Rover Platform Stability During Launch Event
    • Ensure that Lander is not damaged

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Future Work (2)

  • 5) Power System Reduction Options
    • Power system could be reduced by increasing rail length

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  • 6) Larger Electromagnetic Gun
    • How does the system scale for larger applications

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  • 7) Use Non-Simplified Equations for Rail Gun
    • These could potentially show some show stoppers once the details are added back in.

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  • 8) Solar Electric Propulsion Fetch Orbiter Conceptual Design

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Summary

  • Reusable launch system

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  • Can be operated remotely or support astronauts in-situ

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  • Allows for more varied and faster sample processing

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  • Numerous capabilities for the commercial sector

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  • Expandable technology for lunar mining

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From

Prospecting

To

Mining

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QUESTIONS?

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BACKUP

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Lunar Prospecting Rover Abstract

  • Lunar samples have provided a wealth of information on planetary formation. All Apollo lunar samples to date have been recovered by manned missions, resulting in samples from six locations. Increasing the diversity of samples from various lunar sites could lead to further insight into the evolution of the solar system and also how the Moon and planets are formed. Since the Moon has been geologically dormant for long, careful sampling from specific regions may also help us to learn more about solar activity over geologic time. Since the termination of the Apollo and Lunar programs, no new lunar samples have been brought back in almost five decades. Currently, several nations are planning robotic lunar sample return missions.
  • A lunar orbiting station is being planned with orbit-to-surface tele-robotics as a prime technology that is integral to this facility as well as a critical architectural element for future planetary exploration vehicles. The proposed lunar polar orbit would allow this station to closely examine wide swaths of lunar terrain for detailed investigation of resources and potential landing and settlement sites in advance of deploying landers and vehicles to explore and eventually develop lunar surface infrastructure.
  • A concept architecture proposal is presented for a Lunar Prospector & Sample Return Rover that can be operated autonomously, telerobotically, or in-situ. The proposed rover will launch lunar encapsulated samples to be retrieved by an existing Lunar Station that is in low-lunar orbit through propellant-less means. The reusable, propellant-less concept for lunar sample retrieval will extend the range and operational life of the sample rover.
  • Using a telerobotically operated mobile system to pick up samples from the surface, small sample specimens from various regions are encapsulated and launched to low lunar orbit where it is captured and retrieved by an electric propulsion-based chaser system. After rendezvous and capture, the sample capsule is delivered to the orbiting station for study or for return to Earth. The chaser system architecture is part of this concept but not detailed in this presentation. It is planned for future studies.
  • A roving sample return platform would be capable of returning a variety of samples from different regions of the Moon. Such a Lunar Prospector & Sample Return Rover system architecture can provide an augmented lunar prospecting and sample return capability by involving industry that is already working on key technologies that would be required for such a program to be feasible.
  • The capability to augment the prospecting rover into a mining system is discussed.

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Issue Mitigations�Sample Acceleration and Impulse to Lander

  • Sample Acceleration
    • The gun fires off the sample system at a high acceleration ~520g
    • Mars sample return testing performed by JPL for DS-2 has shown sample systems capable of surviving 20,000g impacts

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  • Impulse to Lander from Launch
    • The large acceleration imparted to the sample system is offset by an impulse imparted to the launch rover
    • Assuming a 32Kg sample and a 1740Kg rover the rover will experience ~5g for 1 sec resulting in about 16.6KNs impulse; or firing 6 star 4 motors

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Star 4

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Railgun Theory

Vm=(2DF/m)^.5=(2DILB/m)^.5=I(2DLu/m)^.5

  • Vm=Muzzle velocity (Meters/Second)
  • D=Length of rails (Meters)
  • m=Mass of projectile (Kilograms)
  • I=Current through projectile (Amperes)
  • L=Width between rails (Meters)
  • u=1.26x10^-6 (The magnetic permeability of free space,Henries/Meter)

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  • Electric Force
    • F = ½ L I^2
    • F = force
    • L = rail gun inductance
    • I = current
  • Acceleration imparted to sample system
    • m a = ½ L I^2
    • a = 1/m ½ L I^2
    • Or
    • a = dv/dt

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Sources and References

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