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Launch Vehicle MLI (LVMLI)

The product family includes Launch Vehicle MLI (LVMLI), which offers the insulating properties of IMLI with a robust structure and more durable outer layer to withstand aerodynamic launch loads. LVMLI offers more structural strength than IMLI to withstand aerodynamic loads in the launch environment. LVMLI can help reduce boiloff losses, enabling longer on-orbit coast times for cryogenic upper stages. LVMLI has successfully completed thermal and structural testing, validated some thermal and aerodynamic properties with testing, and is ready for R&D for integration into a launch vehicle and additional aerodynamic and aerothermal testing .

Launch Vehicle–MLI (LVMLI) is an innovative thermal insulation robust enough to survive launch on the outside of launch vehicles and provide high on-orbit thermal performance for reduced boiloff of cryopropellants. During LVMLI Phase I the team designed, built and tested a robust LVMLI system that had a measured heat leak of 3.46 W/m2 for a 3 layer blanket (with areal mass of 0.35 kg/m2), and withstood aerodynamic shockwave and vibration loads of an Atlas launch ascent profile.  The LVMLI prototype had 68-fold lower heat leak than 0.75” SOFI tank insulation, and 43% of 0.75" SOFI mass.  Feasibility of LVMLI was successfully demonstrated with a component laboratory validation and performance close to that modeled, moving the technology from TRL2 to TRL4.

One goal for LVMLI was to reduce heat leak by half over current state-of-the-art SOFI, or to have a heat leak <47 W/m2 (half of 95 W/m2 heat leak through SOFI plus white paint), and LVMLI achieved a heat leak of 3.46 W/m2.  LV-MLI reduced the heat leak through bare, unpainted SOFI foam (236 W/m2) by 98.5%.

 

Another goal was to demonstrate the survivability of LVMLI in the aerodynamic launch environment. A collaborative effort of NASA, ULA, Ball Aerospace and Quest established preliminary aerodynamic and thermal requirements for LVMLI.  Atlas Centaur aerodynamic launch profiles were used to design an aerodynamic launch simulation test fixture that delivered 2.5psi air pressure over 10cm at 18Hz (simulating shockwave attachment loads).  Static and dynamic Finite Element Analysis was performed, and predicted LVMLI would maintain structural integrity during launch ascent. Three LVIMLI configurations were fabricated and tested under aerodynamic loading, and survived with no damage to the structure, mylar or spacers. One coupon tested LVMLI bonded over SOFI, a likely initial flight configuration, with no degradation. Coupons underwent vibration testing at the GEVS 14.6Grms profile with no damage. Compressive and shear loads were applied to measure the strength of the spacers, and compared to modeled values.

Thermal performance was modeled via a network Thermal Analysis Kit thermal model that included various conductive and radiative heat flows between layers and through the discrete spacers.  The thermal model accurately predicts IMLI and LVMLI thermal performance over the range of 20K to 295K. 10-layer IMLI heat flux was predicted to be 0.95 W/m2 and measured at 0.95 W/m2 via boiloff calorimetry. A three layer LVMLI was predicted to have 3.56 W/m2, in fair agreement with a measured 3.46 W/m2. IMLI allows accurate thermal performance calculations, typically within 5 to 10% over the range of 20K to 295K. The thermal model predicts that a 2 layer LVMLI system could provide a heat leak of 5.73 W/m2 (2.4% of the heat leak of 0.75" SOFI), with a mass as low as 0.16 kg/m2 (20% of the mass of 0.75" SOFI).

LVMLI uses Quest Thermal's proprietary and patented Discrete Spacer Technology™ in a rugged bonded up structure. It could be bonded to the sidewalls of LOX/LH2 cryotanks in the Centaur/DCSS/iCPS/Vulcan ACES or other cryogenic second stage vehicles, and withstand aerodynamic loading during launch ascent.  LVMLI can significantly decrease heat flux into upper stage cryotanks and increase payload capacity for NASA, national security and commercial missions that require multi-hour coasts for MEO and GEO orbit insertion, or as part of a Zero Boil Off full system.

This Phase I program evaluated Launch Vehicle-MLI aerodynamic and thermal requirements, designed an LVMLI insulation system, designed and built an aerodynamic simulator, built and tested LVMLI prototypes, installed a 3 layer LVMLI structure on a small test, tested thermal performance via LN2 boiloff calorimetry, built and struturally tested coupons, had thermal performance closely matching that modeled, successfully demonstrated the feasibility of LVMLI, and reached TRL4.

Performance Compared to SOFI

Launch Vehicle MLI

Cryogenic upper stages on launch vehicles have payloads limited partly by on-orbit coast times and propellant boil-off, and LVMLI provides an insulation solution with high thermal performance and low mass. LVMLI has 144x lower heat transfer per thickness than SOFI. For a 200 m2 tank, the difference in propellant lost to boil-off is estimated at 3600kg over 10 hours. LVMLI mass is estimated as 70kg, SOFI mass is 160kg. As a low-risk path to flight demonstration, LVMLI could be used over top of SOFI to provide both ground hold and long on-orbit coast times.