PosterPDF Available

Modelling Sensitivities and Knowledge Gaps Associated with Mars atmosphere Destructive Entry Applied to Planetary Protection

Authors:
  • Fluid Gravity Engineering Ltd
Poster

Modelling Sensitivities and Knowledge Gaps Associated with Mars atmosphere Destructive Entry Applied to Planetary Protection

Abstract

Within the context of space exploration, there is an obligation on space agencies and mission planners to sensibly limit the potential for biological contamination of celestial bodies. These limits are most stringent for celestial bodies that are of significant interest for chemical evolution or the origin of life, and where there is a significant chance that contamination could compromise future or present investigations. Mars[1]and Icy Moons are prime examples of celestial bodies for which careful planetary protection is mandated and mission planners are required to justify and document their approach to demonstrate compliance with the relevant COSPAR recommendations. These do not only apply to probes, but also to any carrier vehicle that might impact on the surface of the celestial body. For celestial bodies with an atmosphere, there is an opportunity to auto-sterilize material during planned destructive entry due to aeroheating. The justification of this approach requires a modelling capability for destructive entry which includes high speed aerodynamics, aerothermodynamics and high temperature material response.This analysis is currently undergoing a resurgence of interest in Europe and elsewhere, mainly to support ground casualty risk assessments associated with end-of-life disposal of satellites in LEO. The cost-benefit of a destructive entry when compared with a controlled re-entry motivates this interest. This has resulted in the creation of several investigative activities within the last five years aimed at increasing the understanding of destructive entry and ultimately improving predictive methodologies. Lessons learnt from these investigations can be applied to planetary protection scenarios. This poster aims at highlighting the possible impact of this new knowledge with respect to Mars planetary protection.
Introduction
Mars[1] and Icy Moons are prime
examples of celestial bodies for
which careful planetary protection is
mandated
This does not only apply to probes,
but also to any carrier vehicle that
might impact on the surface
For Mars, there is the opportunity to
auto-sterilise the carrier vehicle
during destructive entry
Sterilisation of a component is
considered at: complete demise, or
0.5s above 5000C.
For components that do not reach
these criteria, expected bioburden
can be calculated from temperature
chronology
Typically, over 100 “box level”
components are considered in the
analysis
Clear parallels can be drawn with
terrestrial analysis of LEO satellite
at end of life disposal
Modelling Sensitivities and Knowledge Gaps Associated with Mars-
atmosphere Destructive Entry Applied to Planetary Protection
Jim Merrifield1, James Beck2, Juergen Kempf3and Raphael Lescouzeres3
1Fluid Gravity Engineering Limited, 2Belstead Research Limited , 3OHB System AG
Secondary Fragmentation
Component Failures
Two components considered:
Battery and Large Electronics
Box.
Each constructed as an aluminium
housing containing smaller parts.
The battery model releases blocks,
and then cells. The electronics box
releases GFRP cards.
The battery shows complete
sterilisation on fragmentation to
cells.
The electronics box does not reach
sterilisation if the release of the
GFRP cards occurs after complete
melting of the housing.
Allowing the cards to release at the
melt point of the housing results in
complete sterilisation.
Model Fidelity
Important components can be
identified from Monte-Carlo analysis
Utilise CFD to study aerodynamics
and heating to these components
The engineering model was found
to be gently conservative
compared with CFD (slightly lower
integrated heating)
Significant knowledge gaps still
exist concerning fragmentation
criteria and fragmentation chain
Fragmentation models based on
joint failure (e.g. panel inserts)
have been implemented in SAM [6]
Additional empirical data needed
to calibrate and verify this approach
Presently, stochastic approaches
represent the most promising way to
treat these modelling uncertainties
Fragmentation Altitude and
Trajectory Analysis
Atmospheric columns without
temporal and spatial variation
demonstrated as sufficient.
Monte Carlo of 2000 columns
generated from EMCD using
MarMITE[2] tool.
Relevant columns selected from
available Mars Year data and
solar longitude range.
Sterilisation Monte-Carlo analysis
includes atmospheric and entry
state vector uncertainties ~20,000
entry scenarios utilising HPC.
Results are sensitive to
catastrophic breakup altitude. A
variation of 15km in breakup
altitude leads to greater than factor
of 2 change in the number of
sterilised objects. Higher breakup
sterilises more objects.
Terrestrial destructive entry codes
typically specify a breakup altitude
of 78km [3]
Equivalent heat load and dynamic
pressures occur at lower altitudes
for Mars entries ~(35-50 km)
General findings
A novel Monte-Carlo analysis
including secondary
fragmentation events has been
performed for a Mars probe carrier
vehicle
The number of objects that can be
considered auto-sterilised is
strongly driven by fragmentation
altitude.
Debris items that can be considered
to almost always sterilise, and those
that won’t can be determined.
Conservative models should be
used for this initial screening
This can result in a relatively small
list of high impact components,
which can be studied in more detail
(e.g. using CFD)
Secondary fragmentation of
problem-components can lead to
higher levels of sterilisation. Such
an analysis needs to be well
justified
A17
Bibliography
[1] D. L. DeVincenzi, P. Stabekis and J. Barengoltz,“Refinement of planetary protection policy for
Mars missions”, Advances in Space Research, Volume 18, Issues 1–2, 1996, Pages 311-316
[2] A. El-Said et al. “The Mars Modelling Information Tool for Engineering (MarMITE): A study on the
Impact of Local Dust Storms.” In: 1st British Planetary Science Congress, 3-5 Dec 2017, Glasgow
[3] E. Stansbery and J. Opiela, “Debris Assessment Software User’s Guide Version 2.1”, NASA/TP-
2016-218600-REV1
[4] J. Merrifield et al. “Aerothermal Heating Methodology in the Spacecraft Aerothermal Model
(SAM)”, The 7th IAASS Conference, Friedrichshafen, Germany -20-22 Oct 2014
[5] Couchman B, Haynes, M, “Navier-Stokes Computations for Hollow Cylinders and Cubes
Relevant for Satellite Debris”, 8th European Symposium on Aerothermodynamics for Space
Vehicles, March 2015.
[6] J. Beck et al. “Progress in Hybrid Spacecraft/Object Oriented Destructive Re-Entry Modelling
using the SAM Code” Proc. 7th European Conference Space Debris Darmstadt, 2017
Engineering Model: SAM [4] CFD: ANITA [5]
Catastrophic breakup
Debris
fragment
demise
Debris fragment impact DM landing
External solar panel separation
DM separation from CM
ResearchGate has not been able to resolve any citations for this publication.
Conference Paper
Full-text available
Spacecraft are typified by complex geometries meaning that predictive tools designed to assess entry, break up and ground casualty risk are not naturally suited to high fidelity modelling treatments (e.g. the CFD and FE analysis which are prevalent in the assessment of entry vehicle design and performance). Simplifying assumptions are inevitable and the consequences of these simplifying assumptions need to be investigated and quantified. The present paper is concerned with the effect of these simplifying assumptions on ground casualty risk. Specifically we report on work concerning: (i) a discussion and appraisal of some current aeroheating models as implemented in well-known tools (ii) proposed potential improvements to existing models and (iii) novel approaches to aeroheating engineering modelling. These topics are investigated in the framework of the recently developed Spacecraft Aerothermal Model tool (SAM) which can be configured to calculate ground casualty risk using varying degrees of aerothermal and break up model complexity. This allows us to investigate the sensitivity of ground casualty risk to simplifying assumptions. Parameter studies performed so far have highlighted the sensitivity of ground casualty risk to the treatment of fragment aeroheating. SAM has the option to calculate the aeroheating to fragments taking the component size, orientation and shape into account. This goes beyond simple panel inclination methodologies in common use, but is nonetheless based on established engineering correlations. As far as the authors are aware, such a methodology is not currently used by any of the well- known spacecraft breakup tools. The consequence of this novel treatment of fragment heating is the main topic of the current paper.
Article
Under existing COSPAR policy adopted in 1984, missions to Mars (landers, probes, and some orbiters) are designated as Category IV missions. As such, the procedures for implementing planetary protection requirements could include trajectory biasing, cleanrooms, bioload reduction, sterilization of hardware, and bioshields. In 1992, a U.S. National Research Council study recommended that controls on forward contamination of Mars be tied to specific mission objectives. The report recommended that Mars landers with life detection instruments be subject to at least Viking-level sterilization procedures for bioload reduction, while spacecraft (including orbiters) without life detection instruments be subject to at least Viking-level pre-sterilization procedures for bioload reduction but need not be sterilized. In light of this, it is proposed that the current policy's Category IV and its planetary protection requirements be divided into two sub-categories as follows: Category IVa, for missions comprising landers and probes without life detection experiments, which will meet a specified bioburden limit for exposed surfaces, and Category IVb, for landers and probes with life detection experiments, which will require sterilization of landed systems. In addition, Category III orbiter mission specifications are expanded to be consistent with these recommendations.
The Mars Modelling Information Tool for Engineering (MarMITE): A study on the Impact of Local Dust Storms
  • A El-Said
A. El-Said et al. "The Mars Modelling Information Tool for Engineering (MarMITE): A study on the Impact of Local Dust Storms." In: 1st British Planetary Science Congress, 3-5 Dec 2017, Glasgow
Debris Assessment Software User's Guide Version 2.1
  • E Stansbery
  • J Opiela
E. Stansbery and J. Opiela, "Debris Assessment Software User's Guide Version 2.1", NASA/TP-2016-218600-REV1
Navier-Stokes Computations for Hollow Cylinders and Cubes Relevant for Satellite Debris
  • B Couchman
  • M Haynes
Couchman B, Haynes, M, "Navier-Stokes Computations for Hollow Cylinders and Cubes Relevant for Satellite Debris", 8th European Symposium on Aerothermodynamics for Space Vehicles, March 2015.
Progress in Hybrid Spacecraft/Object Oriented Destructive Re-Entry Modelling using the SAM Code
  • J Beck
J. Beck et al. "Progress in Hybrid Spacecraft/Object Oriented Destructive Re-Entry Modelling using the SAM Code" Proc. 7 th European Conference Space Debris Darmstadt, 2017