
The Industrial Crystallization Facility (ICF) is a commercial in-space manufacturing device designed to provide proof-of-principle for diffusion-based crystallization methods to produce high-quality optical crystals in microgravity relevant for terrestrial use. ICF launched to the International Space Station (ISS) on Northrop Grummanās CRS-15 on February 20, 2021.Ā
Expanding onĀ RedwireāsĀ space-enabled manufacturingĀ capabilities, the ICFĀ missionĀ focuses on advanced materials engineering to explore diffusion-based crystallizationĀ methods that areĀ not viableĀ on EarthĀ because ofĀ thermalĀ convection.Ā Ā Space-enabled manufacturingĀ leverages microgravity toĀ produceĀ materials that are either completely new orĀ enhancedĀ comparedĀ toĀ theirĀ counterparts onĀ Earth.Ā These materials could improveĀ performanceĀ of industrial machines and systems that we use on Earth.Ā Ā ICFĀ will offerĀ important insightĀ intoĀ microgravity-enabledĀ growth processes for industrial crystals,Ā which could yield opportunities forĀ commercial production on-orbit.Ā Ā


RedwireĀ has identifiedĀ a solution growth technique targeting potassium dihydrogen phosphate (KDP), a type of nonlinear optical (NLO) crystal.Ā KDPĀ crystals haveĀ beenĀ studiedĀ since the 1930sĀ and commonly used within industry, includingĀ well-definedĀ laserĀ applications.Ā These crystals are often subject to laser-induced damage which limits the output of the system. This damage is often caused by impurities created during the crystal growth process.Ā WithĀ ICF, diffusion-based crystallization techniquesĀ canĀ avoid growth disturbances from thermal convectionĀ toĀ potentiallyĀ yieldĀ crystals with high optical quality that may be used to produce improved laserĀ componentsĀ on Earth.Ā This will be the first time a KDP crystalĀ has beenĀ grownĀ aboard theĀ ISS.Ā Ā
TheĀ KDPĀ Growth ProcessĀ in MicrogravityĀ
There are several crystal growth techniques,Ā with each growth process optimized for various types of crystals.Ā RedwireāsĀ objectiveĀ with ICFĀ is toĀ evaluateĀ KDP crystalĀ growth processĀ in microgravityĀ andĀ establishĀ aĀ baseline comparison between terrestrial and on-orbit KDP crystals as well as key end-use applications.Ā Ā
Existing low-temperature solution growth methods take daysĀ orĀ weeks to complete, so parabolic flights and suborbital vehicles are not suitable for establishing process baselines and making effective comparisons.āÆĀ


ICFĀ eliminatesĀ the negative effects ofĀ thermalĀ convectionĀ onĀ diffusion growth ofĀ theĀ crystalĀ in microgravity.āÆThrough the solution growth technique,Ā the gravity independent diffusion process could yield a much higher laser damage threshold with fewer inclusionsĀ and defects.Ā Ā
With the successful completion and understanding of the diffusion process in microgravity, this growth technique can be applied to other materials and crystals that are currently being identified byĀ RedwireĀ as having high-return commercial use cases onĀ Earth.Ā Ā

ApplicationsĀ of Space-Enabled CrystalsĀ Ā
KDP crystals are used for a variety of applications,Ā including high-power, large laser systems.Ā Because of theirĀ good UV transmission, highĀ laserĀ damage threshold and birefringence, KDP crystals are among the most widelyĀ used commercial NLO materials.Ā KDP crystals are usually used for doubling, tripling and quadrupling ofĀ Nd:YAGĀ laserĀ systemsĀ at room temperature.Ā Ā
Other applicationsĀ for KDP crystalsĀ includeĀ electro-opticĀ modulators, Q-switches, ultrasonicĀ transducers, frequencyĀ doubling and high-power laser frequency conversion for fusion research. The NLO crystal market, whichĀ includes several different NLO crystals, including KDP,Ā is estimated to be worth $7.8B byĀ 2026.Ā Ā
CommercializationĀ Ā
ICF represents another near-termĀ opportunity to spur demand inĀ low-Earth orbitĀ (LEO)Ā by leveraging a commercial capabilityĀ thatĀ deliversĀ value to industries on Earth.Ā This technology also expands utilization ofĀ the ISS intoĀ previously uninvestigatedĀ optical products.Ā ICF is an EXPRESS rack singleĀ locker-sized module with interchangeableĀ components,Ā makingĀ the facilityĀ readily available for future crystal growth experiments.Ā


ICF is one ofĀ severalĀ RedwireĀ facilitiesĀ aboard the ISSĀ focused onĀ commercializingĀ space-enabledĀ materialĀ development,Ā such as the recently launchedĀ Ceramics Manufacturing ModuleĀ (CMM). CMMĀ was the first demonstration of stereolithography ceramic fabrication in space. Another facility,Ā theĀ Made In SpaceĀ Fiber OpticsĀ miniatureĀ fiber-pulling machine,Ā focusesĀ on producing high-quality exoticĀ ZBLANĀ fiber forĀ long-haul telecommunicationsĀ purposes. Following the launch of ICF,Ā RedwireĀ plans to launchĀ a superalloy casting moduleĀ to the ISS.Ā Ā Ā Ā
Learn more about ICFĀ mission:Ā Redwire To Launch New Technology to the International Space Station Focused on Improving Laser Optics Products
Related news: International Space Station National Laboratory “Redwire to Develop a New Industrial Crystal Growth Platform on NG-15”