Technical Trade Studies for a Lunar Penetrator Mission

1
Technical Trade Studies for a Lunar Penetrator
Mission
Alan Smith1, Rob Gowen1, Yang Gao2, and Phil
Church6
2
Contents

• Introduction to Penetrators
• MoonLITE Mission
• Technical Trade Studies
• Program Status
• Summary Conclusions

3
What are kinetic penetrators ?

• Low mass projectiles 2-13Kg
• High impact speed 200-500 m/s
• Very tough 10-50kgee
• Penetrate surface few metres
• Perform science from below surface

4

• History ?
• No successful mission yet.
• DS2 failed alongside soft lander.
• Mars96 spacecraft failed to leave Earth orbit.
• Lunar-A cancelled but maybe fly on Lunar-Glob.
• Feasibility ?
• Lunar-A and DS2 space qualified.
• Military have been successfully firing
  instrumented projectiles for many years to
  comparable levels of gee forces into sand,
  concrete and steel.
• 40,000gee qualified electronics exist (and
  re-used)

When asked to describe the condition of a probe
that had impacted 2m of concrete at 300 m/s a UK
expert described the device as a bit scratched!
5
Impact Test
6
MoonLITE
Polar comms orbiter
3

• Delivery and Comms Spacecraft (Orbiter).Deliver
  penetrators to ejection orbit. provide
  pre-ejection health status, and relay
  communications.
• Orbiter Payload 4 Descent Probes (each
  containing 10-15 kg penetrator 20-25 kg
  de-orbit and attitude control).
• Landing sites Globally spaced Far side, Polar
  region(s), One near an Apollo landing site for
  calibration.
• Duration gt1 year for seismic network. Other
  science does not require so long (perhaps a few
  Lunar cycles for heat flow and volatiles much
  less).
• Penetrator Design Single Body for simplicity
  and risk avoidance. Battery powered with
  comprehensive power saving techniques.

Far side
4
2
1
7
MoonLITE Payload Key Objectives
8
MoonLITE
9
Consider some Technical Challenges

• Descent - deceleration, ACS
• Structure material, design
• Comms regolith, aerial
• Lifetime power, thermal

(Others include data handling, impact physics,
instruments..)
10
Descent Systems Trade Study

• Desire-
• Landing ellipse not too large
• Impact angle lt45? to vertical
• Attack angle lt8?
• Impact speed 300ms

• Constraints
• mass
• impact site contamination

PDS Payload Delivery System Baseline 13Kg
penetrator
Penetrator separation system
ACS
Spacecraft ejection system
De-orbit Motor

• PDS land away from penetrator
• Orientation disturbance of penetrator

• Ensure orientation
• Attack angle control (mass)

• Mechanism ?
• Spinning ?

• Penetrator mass
• Fuel type (mass)
• Impact angle

Does not have to survive impact

• Landing ellipse size

11
Penetrator Structure Trade Study

• Require-
• Survive impact
• Ensure penetration depth 2-5m
• Restrict deflection during impact
• Minimise forces on internal systems

• Constraints
• mass
• impact site contamination

Penetrator Baseline 13kg 120mm diameter 60cm
long
Material
Design

• Payload gt size gt mass
• Diam/length ratio (impact deflection)
• Penetration depth (shape)
• Strength (apertures)
• Integratibility/harnessing
• gt thermal

is the only material which could allow heat
flow without external thermal insulation
12
Communications Trade Study

• Require-
• Survive impact
• Communicate to orbit from beneath regolith
• Receive commands from orbit
• Possibly help with azimuthal orientation

Communications Baseline Beagle2 Melacom,
6W.hr. One 90sec contact/15days Avg tel
30kbits/day Avg cmd low.

• Constraints
• mass
• power

Issues
technology

• Power vs Regolith attenuation (ice/volatiles,
  penetration depth ?)
• Communication strategies gt power
• Commanding gt seismometer event
• coordination

• Receiver/transmitter
• Patch aerial (polarisation)
• Trailing antennae ? ( aid heat flow
  measurement)

13
Power-Thermal Trade Study
Power Baseline 500Wh, 2kg batteries solar cells
not at poles fuel cells not studied RPG
when available

• Constraints
• mass/size
• rugged

Desire mission lifetime ?1year for seismometry
RHUs Keep batteries warm
Subsystems instruments
Heat losses

• 2 very different external environments-
  equator 250K very cold poles 50-100K
  unknown conductivity (ice at poles?)
• Thermal design keep batteries warm
  external/internal insulation parasitic heat
  losses through wires

• Payload complement
• Low power components
• Low power operating modes
• seismometer monitoring mode
• limited comms periods
• Fallback -gt reduce seismometer lifetime at poles

14
MoonLITE Mission Status

• Penetrator Design baseline agreed.
• Full-scale structure impact trial Scheduled
  March 2008
• Pre-mission development - bids in preparation for
  2 yr development to bring ruggedization of
  penetrator subsystems and instruments up to TRL
  5.
• Mission currently in discussion with BNSC and
  NASA

15
Finally

• For further information email as_at_mssl.ucl.ac.uk
  
• or see

http//www.mssl.ucl.ac.uk/planetary/missions/Micro
_Penetrators.php
the MoonLITE penetrators have the potential to
make major contributions to lunar science. Ian
Crawford, 2007.
16
- End -
17
Science ISRU Objectives
3

• Characterize water, volatiles, and
  astrobiologically related material at lunar
  poles. gt Water is key to manned missions
• Constrain origin, differentiation, 3d internal
  structure far side crustal thickness of moon
  via a seismic network.
• Investigate enigmatic strong surface seismic
  signals gt identify potentially dangerous
  sitesfor lunar bases
• Determine thermal compositional differences at
  polar regions and far side.
• Obtain ground truth for remote sensing instruments

4
2
1
18
MoonLITE
3

• Scientific Instruments (Total mass 2kg)

Far side

• baseline
• descent camera
• accelerometer
• seismometers
• geochemistry package
• thermal package
• options
• mineralogy camera
• radiation monitor
• magnetometer
• etc..

4
2
1
19
Mission Lifetime Trade Study

• 1 year lifetime desired for seismic network
• Power Supply 500Wh. Default is Batteries
  (2kg)
• Solar cells lt- no good at poles
• Fuel cells (not studied)
• RTG (when available)
• Power Usage efficient communications, low power
  seismometer pre-event monitoring, low power
  systems.
• Thermal Issues heat loss, especially at poles
  where temperatures expected 50-100K unknown
  external material conductivity.
• Insulation (surface coating, internal)
• Parasitic heat loss through wires
• RHUs (to heat batteries -gt extend lifetime)
• Fallback reduced (seismometer) lifetime at poles.