Isogrid

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Type of partially hollowed-out structure

title: "Isogrid" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["components", "aerospace-materials"] description: "Type of partially hollowed-out structure" topic_path: "general/components" source: "https://en.wikipedia.org/wiki/Isogrid" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Type of partially hollowed-out structure ::

::figure[src="https://upload.wikimedia.org/wikipedia/commons/e/ef/Orion-Delta_IV_adapter_isogrid.jpg" caption="Isogrid on the interior of the adapter connecting the Orion spacecraft to the Delta IV rocket for [[Exploration Flight Test 1]]"] ::

Isogrid is a type of partially hollowed-out structure formed usually from a single metal plate with integral triangular stiffening stringers. It was patented by McDonnell Douglas (now part of Boeing) in 1975.{{cite conference |url = https://www.iccm-central.org/Proceedings/ICCM12proceedings/site/papers/pap357.pdf |title = GRID STIFFENED STRUCTURES: A SURVEY OF FABRICATION, ANALYSIS AND DESIGN METHODS |last1 = Huybrechts |first1 = Steven M. |last2 = Hahn |first2 = Steven E. |last3 = Meink |first3 = Troy E. |date = July 5–9, 1999 |location = Paris, France |conference = Proceedings of the 1999 International Conference on Composite Materials |access-date = Jan 10, 2020 |quote = The McDonnell-Douglas Corporation (now part of The Boeing Company) holds the patent rights for development of the first aluminum isogrid |archive-date = December 22, 2019 |archive-url = https://web.archive.org/web/20191222012416/http://www.iccm-central.org/Proceedings/ICCM12proceedings/site/papers/pap357.pdf |url-status = dead Isogrids are extremely light and stiff.{{Cite thesis |type=PhD |last=Black |first=Jonathan T. |date=2006 |url=https://uknowledge.uky.edu/gradschool_diss/390/ |title=NEW ULTRA-LIGHTWEIGHT STIFF PANELS FOR SPACE APERTURES |publisher=University of Kentucky Doctoral Dissertations |access-date=Jan 10, 2020}} Compared to other materials, it is expensive to manufacture, and so it is restricted to spaceflight applications and some aerospace use.

Theory and design

::figure[src="https://upload.wikimedia.org/wikipedia/commons/c/c5/Isogrid_topview.png" caption="Top view of isogrid panel" alt=""] ::

::figure[src="https://upload.wikimedia.org/wikipedia/commons/6/6d/Isogrid_flange.png" caption="Cross-section of isogrid flange stiffener{{cite patent" alt=""] ::

| country = US | number = 4012549 | status = patent | title = High strength composite structure | pubdate = Oct 10, 1974 | gdate = Mar 15, 1977 | fdate = Oct 10, 1974 | inventor = Paul Slysh ]] Isogrid structures are related to sandwich-structured composite panels; both can be modeled using sandwich theory, which describes structures with separated, stiff face sheets and a lighter interconnecting layer. Isogrids are manufactured from single sheets of material and with large-scale triangular openings, and an open pattern to the flanges, compared to closed sheets and foam or honeycomb structures for the sandwich-composite structures.

Isogrid structures are constituted by a thin skin reinforced with a lattice structure. Such structures are adopted in the aeronautical industry since they present both structural resistance and lightness.

The term isogrid is used because the structure acts like an isotropic material, having the same properties along any axis. Traditionally, the equilateral triangle pattern was used because it was amenable to simplified analysis. |url=https://femci.gsfc.nasa.gov/isogrid/NASA-CR-124075_Isogrid_Design.pdf |title=Isogrid Design Handbook |author=McDonnell Douglas Astronautics Company |date=February 1973 |publisher=NASA |number=NASA CR-124075 |access-date=Jan 10, 2020 |page=1.0.002 (12/252)}} |last1 = Meyer | first1 = R. R |last2 = Harwood | first2 = O. P. |title = Isogrid design handbook |publisher = Marshall Space Flight Center |date = Oct 1, 1973 |orig-year = 1973 |url=https://ntrs.nasa.gov/search.jsp?R=19730000395&qs=Ns%3DNASA-Center%7c0%26N%3D4294753258 |id=19730000395 OrthogridA variant is the orthogrid (sometimes called a waffle grid), which uses rectangular rather than triangular openings. It is not isotropic (has different properties in different orientations), but matches many use cases well and is easier to manufacture.

Manufacturing

The stiffeners of an isogrid are generally machined from one face of a single sheet of material such as aluminium with a CNC milling machine. A thickness less than 0.04 in might require chemical milling processes.{{cite web | url = http://www.isogrid-sst.com/machine%20design.htm | archive-url = https://web.archive.org/web/20120324153516/http://www.isogrid-sst.com/machine%20design.htm | archive-date = March 24, 2012 | url-status = live | title = The Isogrid | first = Paul | last = Slysh | access-date = May 27, 2011

A major push has been made toward additive manufacturing techniques due to a decrease in overall material and production costs and high efficiency and accuracy while providing control over parameters like porosity. Also, the ease of prototype manufacturing for testing purposes has made a huge contribution.

Composite isogrids are rib-skin configurations, where at least a part of the rib is a different material from the skin, the composite assembled by various manual or automated processes.{{cite journal | last = Huybrechts | first = Steven | author2 = Troy E. Meink | author3 = Peter M. Wegner | author4 = Jeff M. Ganley | title = Manufacturing theory for advanced grid stiffened structures | journal = Composites Part A: Applied Science and Manufacturing | volume = 33 | issue = 2 | pages = 155–161 | publisher = Elsevier | year = 2002 | url = http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA430878 | archive-url = https://web.archive.org/web/20160304055254/http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA430878 | url-status = dead | archive-date = March 4, 2016 | access-date = 26 May 2012 | doi = 10.1016/S1359-835X(01)00113-0 | url-access = subscription This can give extremely high strength-to-weight ratios.{{Cite conference | last1 = Wegner | first1 = Peter M. | last2 = Higgins | first2 = John E. | last3 = VanWest | first3 = Barry P. | title = Application of Advanced Grid-Stiffened Structures Technology to the Minotaur Payload Fairing | book-title = 43rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference | place = Denver, CO | year = 2002 | url = http://handle.dtic.mil/100.2/ADA510804 | archive-url = https://web.archive.org/web/20120527163248/http://handle.dtic.mil/100.2/ADA510804 | url-status = dead | archive-date = May 27, 2012

Uses

::figure[src="https://upload.wikimedia.org/wikipedia/commons/a/a3/CST-100_pressure_vessel.jpg" caption="Isogrids on the [[CST-100]] pressure vessel"] ::

Isogrid panels form self-stiffened structures where low weight, stiffness, strength and damage tolerance are important, such as in aircraft or space vehicles. Aerospace isogrid structures include payload shrouds and boosters, which must support the full weight of upper stages and payloads under high G loads. Their open configuration with a single, sealed sheet facing the outside makes them especially useful for propellant tanks for rockets, where sealing the propellant in, but allowing it to drain in use or maintenance are necessary features.

Examples

Some spacecraft and launch vehicles which use isogrid structures include:

  • Delta families{{Citation |last = Knighton |first = D. J. |title = Delta launch vehicle isogrid structure NASTRAN analysis |journal = Nastran: Users' Experiences |publisher = Goddard Space Flight Center |date = Sep 1, 1972 |orig-year = 1972 |hdl = 2060/19720025227 |url = https://ntrs.nasa.gov/search.jsp?R=19720025227 |archive-url = https://web.archive.org/web/20210129191829/https://ntrs.nasa.gov/search.jsp?R=19720025227 |archive-date = January 29, 2021 |access-date = July 7, 2017 |url-status = bot: unknown
  • Atlas families
  • Skylab space station Orbital Workshop module
  • SLS Core Stage{{cite web |url=https://www.spacelaunchreport.com/sls7.html |archive-url=https://web.archive.org/web/20140404120940/http://spacelaunchreport.com/sls7.html |url-status=usurped |archive-date=April 4, 2014 |title=Progress on NASA's Space Launch System and Orion |last= Kyle |first= Ed |date=Jan 26, 2014 |website=Space Launch Report |access-date=Jan 10, 2020 |quote=Boeing's SLS core will use AL-2219 Aluminum machined with isogrids}}
  • CST-100 Starliner
  • SpaceX Crew Dragon

Orthogrid

Orthogrid (also known as waffle grid) is similar to isogrid, but with a square pattern; examples include:

  • Saturn rocket tanks, due to the lower cost and ease of manufacture{{Citation | last = Wagner | first = W. A. | title = Liquid rocket metal tanks and tank components | publisher = NASA Lewis Research Center | date = May 1, 1974 | orig-year = 1974 | hdl = 2060/19750004950 | pages = 55–58 | url = https://ntrs.nasa.gov/search.jsp?R=19750004950 | archive-url = https://web.archive.org/web/20210130173055/https://ntrs.nasa.gov/search.jsp?R=19750004950 | archive-date = January 30, 2021 | access-date = November 26, 2019 | url-status = bot: unknown
  • Vulcan rocket
  • New Glenn rocket tanks
  • Space Launch System core stage tanks

References

References

  1. "Stiffened composite structural member and method of fabrication".
  2. (2016-05-20). "Design and manufacturing of an isogrid structure in composite material: Numerical and experimental results". Composite Structures.
  3. "Evolution in Manufacturing of Grid Stiffened Structures through CAM and Additive Techniques".
  4. "Atlas V 500 series". United Launch Alliance.
  5. (23 June 2014). "Boeing displays CST-100 progress at Kennedy Space Center". [[SpaceNews]].
  6. Editor, SpaceRef. (2010-10-05). "SpaceX Update: COTS Demonstration Flight 1 (with photos)".
  7. Bruno, Tory. (Apr 20, 2017). "Orthogrid trial panel for Vulcan Rocket propellant tank. (Bigger than it looks...)".

::callout[type=info title="Wikipedia Source"] This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page. ::

componentsaerospace-materials