HESE structures are a relatively new type of structures that were invented in the early 2000’s.  The term “HESE” stands for “Hydrostatically Enabled Structural Element.” It refers to the underlying structural phenomenon that allows the roof beams to carry load.  The HESE beams in the illustration would be composed of tubular membranes filled with lunar regolith.  Tensile stresses in the membranes confine and compress the regolith and place the regolith under a compressive hydrostatic state of stress.  This increases the shear strength and the stiffness of the fill.  The HESE beams owe their load carrying ability and their stiffness to the hydrostatic stress.  They are thus “enabled” by this hydrostatic stress.  The beams have this response because the regolith fill exhibits what is known as frictional “Mohr-Coulomb” response.

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Frictional Mohr-Columb materials (Coulomb, 1776; Mohr, 1900) include many geologic materials that are abundant and widespread on Earth, such as sands, gravels, crushed rock, and desert alluvia.  Frictional Mohr-Coulomb materials are believed to be widespread and plentiful in lunar regolith (Mitchell et al., 1972) and Martian regolith (Oravec, et al., 2025).

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The fact that some soils exhibit frictional Mohr-Coulomb behavior has been known since the late 1800’s.  This same phenomenon causes vacuum-packed coffee packages to be stiff and have lateral strength even though unpressurized coffee particles have neither characteristic.  What was not known until the early 2000’s is that this phenomenon can be used to construct strong and practical structural beams and columns by compressing Mohr-Coulomb type soils inside of tubular membranes.  This discovery was the result of a joint research program conducted by the US Army Engineer Research and Development Center (ERDC) and the US Army Natick Soldier Center (Doherty, et al., 2009).  The Army researchers were awarded a US patent in 2012 for their discovery (Welch et al., 2012).

 

Planet Z Tech is continuing to develop HESE technology for use on the Earth, Moon, and Mars.  We have teamed with both the Mississippi Polymer Institute of the University of Southern Mississippi, and the Mississippi State University Center for Advanced Vehicular Systems in this effort.  Planet Z’s development team has reexamined the Army’s research and verified their results.  We have extended their findings through additional sub-scale experiments, and have a pending patent that complements the original patent.  

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Using the data from HESE sub-scale laboratory tests, and traditional engineering models (e.g., Euler-Bernoulli Beam Theory), we designed the roof beams for the illustrated HESE 12-Meter Cut & Cover Structure.  The Structure has an unsupported span of 12 m and is 12 m in length.  It is overlain by a 1-m thick overburden of lunar regolith for added protection from radiation and meteor impact.  The Moon’s gravitational field (1/6 that of Earth’s), as well as construction-related loads and the weight of the roof beams themselves, were considered.  The design criteria used was a maximum center deflection of 1/40 of the unsupported span length.  This called for HESE roof beams 1.3 m in diameter.  The high-strength membrane fabric would be either Kevlar® or Vectran®, both of which have had extensive experience in Space use.  For example, Vectran® was used for the decelerating air bags for the Martian Exploration Rovers (Steltzner et al., 2003).  A hydrostatic stress of 0.7 MPa (100 psi) was assumed for the regolith fill.  Additional design details are provided in Welch, et al., (2027). 

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Lunar HESE Cut & Cover Structures would require only tubular membranes to be transported to the Moon, as the remainder of the building material is in situ lunar regolith.  Cut & Cover Structures could be constructed over excavated trenches, or take advantage of highly elongated craters produced by glancing meteor impacts.  For the 12 m by 12 m Structure shown, the membranes would have a total mass of approximately 1,440 kg, and a volume of 2.1 m3.  The transport requirements are well within the capabilities of lunar landers under development by Blue Origin (Blue Moon Mark 2; 30,000-kg payload) (Blue Origin, 2026) and SpaceX (Starship HLS; 100,000-kg payload) (Starship HLS, 2026).  In addition, further optimization of the HESE technology, such as using higher hydrostatic stresses in the fill, could allow HESE membrane mass and volume requirements to be reduced by up to 50 %. 

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The protected area of the proposed HESE 12 Meter Cut & Cover Structure is the largest of any practical lunar structure proposed to date.  It would protect some of the largest of the Inflatable Space Habitats under development, such as the LIFE® 500 system of Sierra Space (SierraSpace.com, 2025) which provides 500 m3 of work and living space.  HESE Cut & Cover Structures of other widths and lengths are also possible.

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The combination of HESE Cut & Cover Structures and Inflatable Space Habitats provides a low transport mass and low transport volume solution to building permanent habitats on the Moon and Mars.  The resultant habitats would result in living and work spaces that are protected from radiation, meteor impact, and rocket plume.  The structural combination offers the quickest near-term habitat solution for permanent lunar and Martian colonization. 

 

References: 

  

1. Bigelow Aerospace, 2025.  Wikipedia Article accessed 5Jan2005. https://en.wikipedia.org/wiki/Bigelow Aerospace

2. Blue Origin, 2026. Blue Moon Mark 1. https://www.blueorigin.com/blue-moon/mark-1

3. Coulomb, C. A., 1776. Essai sur une application des regles des maximis et minimis a quelquels problemesde statique relatifs, a la architecture. Mem. Acad. Roy. Div. Sav., vol. 7, pp. 343–387.

4. Doherty, R.M., Hynes, M.E., Hancock, S.D., Pittman, D.W (Editors), 2009. “Proceedings - Stabilization of Buildings Workshop.” Department of Homeland Security, Memphis, Tn.  25-27Aug2009.  PP 283-285.  https://www.dhs.gov/xlibrary/assets/stabilization-buildings-workshop-0825-08272009.pdf

5. ILC Dover, 2026. “Space Habitats.” ILC Dover website accessed 11Feb2026. https://www.ilcdoverastrospace.com/en/space-habitats/

6. Mitchell et al., 1972. “Mechanical Properties of Lunar Soil: Density, Porosity, Cohesion, and Angle of Internal Friction,” Proceedings of the Third Lunar Science Conference, Vol. 3, PP. 3235-3253, M.I.T. Press, 1972. https://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1972LPSC....3.3235M&defaultprint=YES&filetype=.pdf

7. Mohr, O., 1900. “Welche Umstände bedingen die Elastizitätsgrenze und den Bruch eines Materials Civilingenieur.”

8. Oravec, H.A., Asnani, V. M., Creager, C.M., Moreland, S.J., 2025. “Geotechnical Review of Existing Mars Soil Simulants for Surface Mobility,” https://ntrs.nasa.gov/api/citations/20200003046/downloads/20200003046.pdf 

9. SierraSpace.com, 2025. https://www.sierraspace.com/commercial-space-stations/life-space-habitat/

10. Starship HLS, 2026. “Starship HLS” Wikipedia article accessed 10Feb2026. https://en.wikipedia.org/wiki/Starship_HLS

11. Steltzner, A., Desai, P., Lee, W., Bruno, R., 2003. “The Mars Exploration Rovers Entry Descent and Landing and the Use of Aerodynamic Decelerators,” AIAA ADS Conference, May, 20-22, 2003.  Monterey, CA.

12. Welch, C.R., Abraham, K., Ebeling, R.M., Quigley, C., Buehler, K., 2012. “Hydrostatically Enabled Structural Element.” U.S. Patent #8,209,911, issued 3 July 2012.

13. Welch, C. R., Baylot, J.T., Shirley, C., Edwards, M.K., Stewart, B.C., Monica, M., Rhee, H. “HESE – An Ultra-Low Logistics Building System for the Moon and Mars.” To appear, ASCE Civil Engineering, March/April 2027.