Bailet, Gilles

Hastie, Peter

McInnes, Colin R.

White, Craig

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The Use of In-Space Manufactured Solid Foams for AerocaptureP.G.B. Hastie1, G. Bailet1, C. White1 and C.R. McInnes11James Watt School of Engineering, University of Glasgow, Scotland, UK. G12 8QQFor more information and collaborations: 2591092H@student.gla.ac.ukAcknowledgmentsThis work is supported by a Royal Academy of Engineering Chair in EmergingTechnologies (CMcI, GB, PH)References[1] J. L. Hall, M. A. Noca, and R. W. Bailey, ‘Cost-Benefit Analysis of the Aerocapture MissionSet’, Journal of Spacecraft and Rockets, vol. 42, no. 2, pp. 309–320, 2005, doi:10.2514/1.4118. [2] E. M. Repic, M. G. Boobar, and F. G. Chapel, ‘Aerobraking as a potentialplanetary capture mode.’, Journal of Spacecraft and Rockets, vol. 5, no. 8, pp. 921–926,Aug. 1968, doi: 10.2514/3.29389. [3] A. M. Dwyer Cianciolo et al., ‘Entry, Descent andLanding Systems Analysis Study: Phase 1 Report’, NASA, NASA Center for AeroSpaceInformation,7115 Standard Drive Hanover, 7115 Standard Drive, Hanover, MD 21076-1320,NASA/TM-2010-216720, Jul. 2010. [4] L. J. Gibson and M. F. Ashby, ‘Cellular solids:structure and properties’, 2nd ed. Cambridge: Cambridge University Press, 1997. [5] G.Bailet et al., ‘Radiation and ablation studies for in-flight validation’, 2019. [6] J. T. Schofieldet al., ‘The Mars Pathfinder Atmospheric Structure Investigation/Meteorology (ASI/MET)Experiment’, Science, vol. 278, no. 5344, pp. 1752–1758, Dec. 1997, doi:10.1126/science.278.5344.1752. [7] K. Bhaskar and T. K. Varadan, ‘Plates: Theories andApplications’. York: John Wiley & Sons, 2014. [8] K. Sutton and R. Graves, ‘A generalstagnation-point convective heating equation for arbitrary gas mixtures’, NASA, USA, NASATechnical Report (TR) NASA-TR-R-376, Nov. 1971. Accessed: Jul. 14, 2021. [Online].Available: https://ntrs.nasa.gov/citations/19720003329 [9] C. White, et al., dsmcFoam+: AnOpenFOAM based direct simulation Monte Carlo solver, Computer PhysicsCommunications, Volume 224, 2018, Pages 22-43, ISSN 0010-4655,https://doi.org/10.1016/j.cpc.2017.09.030. [10] D. Lichodziejewski et al., ‘Design andTesting of the Inflatable Aeroshell for the IRVE-3 Flight Experiment’. doi: 10.2514/6.2012-1515.Aerocapture has been investigated as a means of capturing platforms into a planetary orbitusing minimal mass [1]. Using aerocapture, the drag created by the spacecraft traversing aplanetary atmosphere can provide sufficient deceleration to capture it into a bound orbit[2]. The delta-V delivered through aerocapture is a function of the drag force, the mass ofthe platform, the density profile of the atmosphere as well as the entry profile. This posterexplores a novel method of increasing the drag force by using in-space manufactured solidfoams to create a large diameter aeroshell. The density of the foam is critical, as it affectsboth the scale of the aeroshell and the aeroshell’s mechanical and thermal properties. Asensitivity analysis was carried out to find a suitable foam density and aeroshelldimensioning that would be suitable for an aerocapture on Mars. The final aeroshellparameters where then used in a Direct Simulation Monte Carlo (DSMC) to moreaccurately evaluate the mechanical and thermal loads.AbstractFor a given payload mass, there are two options for providing the delta-V required tocapture the spacecraft in the planet's orbit 1) a trajectory with a pericentre in the denserlower atmosphere 2) a grazing trajectory in the upper atmosphere with a large aeroshell.In approach 1 the low minimum altitude results in a high maximum heat flux. In approach2 the platform has a higher minimum altitude and so lower maximum heat flux. A lighterTPS is required for this approach [3] but the diameter of the vehicle needs to be muchlarger for the same effect.In-space manufacturing technology opens the possibility of designing space products thatare tailor made for their application, free from the constraints of ground-basedmanufacturing and launch. In the case of an aeroshell designed for aerocapture, in-spacemanufacturing could enable the construction of an aeroshell with a large diameter and lowmass resulting in an ultra-low ballistic coefficient. This aeroshell would require a highspecific strength to support the deceleration of the spacecraft. Solid foams have highspecific strength and low density [4] so make an interesting candidate material for theaeroshell.The foam aeroshell must be capable of surviving the aerocapture’s atmospheric pass. Tosurvive, the aeroshell must be capable of supporting a high mechanical load and a highheat flux while passing through the atmosphere. This is somewhat of a balance, as higherpasses require larger deceleration to capture the spacecraft in the planet's orbit, whereaslower passes have higher heat flux. To examine the conditions for which a foam aeroshellwould be suitable, a trajectory model was used to carry out a sensitivity study. Mechanicaland thermal models were used to understand whether or not the aeroshell would survive.ContextTrajectory ModelThe trajectory analysis was performed using a 3 degree-of-freedom simulation codedeveloped by Bailet et al [5]. The Martian atmosphere parameters were derived from theresults of the Mars Pathfinder mission [6].A sensitivity analysis was performed assessing the effect of entry flight path angle andballistic coefficient (ß). The baseline geometry of the aeroshell was fixed (see Fig. 2) withonly one variable being the radius of the aeroshell (a). ß was calculated using equations 1and 2.𝛽 =𝑚𝐴𝑆 +𝑚𝑃𝐿𝐶𝑑𝜋𝑎21𝑚𝐴𝑆 = 𝜌𝐹𝑜𝑎𝑚 𝑉𝑜𝑙𝐹𝑟𝑜𝑛𝑡 +13𝜋 𝑎2 + 𝑎𝑏 + 𝑏2 ℎ (2)Here mAS is the mass of the aeroshell, mPL is the mass of the payload, Cd is the dragcoefficient, b is the radius of the central hub containing the payload, h is the thickness ofthe aeroshell, VolFront is the volume of the foam around the central hub, and ρFoam is thedensity of the foam. In addition, the spacecraft has an entry interface speed of 5.5 km/sand a fixed mass of 12.5 tonnes (10 tonnes payload). The target orbit aims for a range ofapoapsis altitude between 30,000 and 40,000 km.Mechanical and Thermal ModelsThe dynamic pressure on the skirt section of the aeroshell is one of the critical parametersto design the mission. Using the Gibson-Ashby model [4], the mechanical properties ofvarious densities of PEEK-based foam were assessed. The aeroshell was modelled as anannulus plate, fully supported by the payload central hub using plate theory [7].The mechanical Factor of Safety (FoS) is derived from this analysis and displayed along sidethe maximal heat flux at the nose in Fig. 1 and represents the maximum stress found bythe mechanical model as a proportion of the tensile yield strength of the foam.Alongside the FoS, Fig. 1 display the peak heat flux at the nose of the aeroshell for thedifferent ballistic coefficients. For this purpose, the Sutton-Graves approximation for Marswas used [8], this will help us determine in future analysis if the nose heatshield could beconstituted of disposable PEEK-based foam or if a traditional TPS needs to be used at thenose.Finally, dsmcFoam+ [9], a direct simulation Monte Carlo (DSMC) solver was used to moreaccurately evaluate the mechanical and thermal loads allowing us to confirm our initialdimensioning. The simulation was performed for a velocity of 5.16 km/s, an altitude of 91km and the geometry shown in Fig. 2.PerformancesThe final aeroshell design was selected based on the mechanical performance. The finaldesign has a foam density of 86 kg/m3, a ß of 12 kg/m2 and an outside diameter of 25.5 m(a=12.75 m). The performance of this aeroshell has been compared with a chemicalpropulsion system and the inflatable entry system HIAD [3] system in table 1. The analysisshows that the aerocapture with a foam aeroshell is able to save half of the allocated massand three quarters of the volume for the same mission compared to the chemicalpropulsion solution. In comparison with a HIAD type system, the foam aeroshell is not ableto perform a full entry but could be a enhancement to HIAD or an intermediate stageallowing a first aerocapture with the foam aeroshell from a more constraininginterplanetary approach before the final entry with HIAD.System Foam Aeroshell HIAD (Ø23m) Chemical PropulsionMission Context12.5 tonne mission Aeroshell Ø25.5 m109 tonne missionAeroshell Ø23 m12.5 tonne missionEngine Isp 370sPercentage of Mission’s Mass20% 25% 40%Storage Volume 3 m3 120 m3 11 m3Ballistic Coefficient (ß) 12 kg/m2 135 kg/m2 N/AHeritage None Demonstrator tested [10] Extensive heritageTable 1: Foam aeroshell performance compared to HIAD and chemical propulsionConclusionThe in-space manufactured foam aeroshell presented in this poster shows promises todeliver a 12.5 tonne mission (10 tonnes payload) in Martian orbit using an aerocapturemanoeuvre (minimum altitude of 91 km).Further studies will allow the validation of thermal and mechanical properties of theproposed PEEK-based foam and demonstrate in-orbit manufacturing of such large scalesystems. This novel approach could allow a drastic change in the future mission conceptwhere qualification and repair of the system in-flight becomes a reality thus increasingsystem reliability.Figure 1: Peak heat flux and mechanical FoS for captured trajectories as a function of ßFigure 2: Cross section of the axisymmetric aeroshell (left) and DSMC results for the maximal heat flux point of the selected trajectory (right)Velocity = 5.15 km.s-1Aeroshell radius (a) = 12.75 mh = 1 mb = 3.5 mPayload

The Use of In-Space Manufactured Solid Foams for Aerocapture

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The Use of In-Space Manufactured Solid Foams for Aerocapture

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