Final test of TMT M1 shipping container at Larson Packaging Company in California, July 2020 -
From right: TMT engineers Fred Kamphues and Ben Gallagher; Larson engineers and management Hector Monrroy, Mark Hoffman, Jason Short, Ray Horner and Gary Fanella; Jack Kiebach (BayAT) and Russel Wosk (Enidine) next to the TMT shipping container prototype -
Image credit: TMT international Observatory
TMT Mirror Segment Shipping Container Design and Prototypes Completed through Collaborative Effort with Larson Packaging Company
Pasadena, CA – TMT, in partnership with Larson Packaging Company, recently celebrated the successful design and completion of TMT’s Primary Mirror Assembly Shipping Container (PMASC). The shipping container will enclose and protect TMT’s primary mirror segments during transport and storage between their international destinations.
Each of the 574 manufactured TMT Primary Mirror segments (M1) (including 82 spare segments) will have its own dedicated shipping container to provide safe transport between TIO partners and the final destination at the construction site. TMT Segment Support Assemblies (SSA) and Polished Mirror Assemblies (PMA) will be manufactured in Japan, China, India and the US. Each TMT M1 container will take at least three long trips through its lifetime, totaling more than 1,700 separate journeys, including final transportation to the site.
Map of TMT Primary Mirror Assembly journeys around the world - Each TMT M1 Segment Support Assembly (SSA) will be fabricated in India and will travel to one of the four mirror integration facilities distributed among TMT partners. M1 segment packages will then be shipped to a US-based facility for undergoing an Ion Beam Figuring optical correction process before their final destination to the observatory site, where they will be integrated with the telescope - Image credit: TMT International Observatory
The Primary Mirror Assembly Shipping Container (PMASC) needs to support the safe transport of TMT’s highly delicate and expensive mirror parts, over multiple destinations, during a journey from a partially- to a fully-assembled segment. The transit path for each PMASC includes all major means of transport such as sea, air, truck and rail, as well as the standard handling equipment (forklifts, trucks, or cranes) used by cargo operators. Each 500-pound TMT segment is extremely fragile and can withstand shocks no greater than seven times the acceleration of Earth’s gravity in the vertical plane, and 3.6 times in the horizontal plane. Additionally, the PMASC needs to be optimized for the multiple loading/unloading of the partially assembled TMT segment.
TMT defined stringent requirements for securing full protection of TMT’s segments during their periods of shipment and storage. TMT selected Larson Packaging Company (LPC) to work on the project, and starting in March 2019, TMT and LPC have worked jointly on the container specifications, design, engineering drawings, and complete instruction guide for manufacturing the PMASC. The use of wire rope isolators was central in providing significant dampening for the extremely fragile TMT segment due to its size, weight, and fragility. Enidine Inc’s wire rope isolators from Bay Area distributor Bay Advanced Technologies (BayAT) were selected for their performance. Both Enidine and BayAT participated with LPC and TMT in the testing and placement of the dampeners within the PMASC.
“Congratulations to the entire container design team, who worked under a global lockdown and very difficult conditions,” said Ben Gallagher, TMT M1 System Lead Engineer. “The LPC team was very flexible and creative, providing the ground for a very good collaboration with TMT. Larson engineers showed critical insight and expert understanding to make this work, and they delivered a very-high quality product.”
TMT Primary Mirror Assembly Shipping Containers (PMASC) - TMT Primary Mirror Assembly Shipping Containers (PMASC)The wooden container is closed at all ends, with a finished size of approximately 2m x 2m x 1m. The design of the container allows the boxes to be placed in a most convenient way. The containers can be stacked three high to form a single unit and bolt to each other for stability during storage and any seismic activity at the site - Image credit: TMT International Observatory / LPC
The heavy-duty PMASC requires few tools to be assembled, dissembled and maintained. Its opening from both top and front sides allows fast loading/unloading of its content, without damaging any of the components.
The PMASC’s unique design provides the high degree of flexibility required to accommodate TMT’s needs, with a positioning frame that can be used with different specific configurations.
TMT’s SSAs will be shipped assembled, first mounted with a dummy mirror segment attached with 27 rods that are used for shipping. The container will then be shipped to the glass manufacturers who will substitute the dummy segment with a polished mirror. After integration of the polished mirror, each PMA will be mounted and protected within the container.
TMT Primary Mirror Assembly Shipping Container (PMASC) Interior - Thanks to LPC’s ingenious design, the SSA “floats” over the M1 segment and they are stored into a zipper-side reusable anti-corrosion bag. Several wire rope isolators are required to keep the material protected from shocks and vibration - Image credit: TMT International Observatory
The combination SSA & PMA will be mounted on a very stable metal frame structure that will hold the primary mirror facing downward, and the SSA will be secured by three custom metal brackets within the wood container. The rigid custom-designed welded frame will be mounted on a floater base with six wire rope isolators that serve as cushioning system to restrain vibration and shock stress.
To minimize potential damages of the PMASC content in case of drop, impact collision, or simply due to rough conditions on the road during transport, it is paramount to keep the shock and acceleration levels as low as possible. In that respect, TMT and LPC conducted three dynamic test campaigns, following the conception and manufacturing of the first container prototype. A series of iterative testing, including vertical drop, side impact and vibration tests, were carried out at the LPC testing facility, with the aim being to assess the capability and quality of the prototype. Few minor revisions were fulfilled to optimize the product and meet TMT requirements, and a complete final test campaign using a full-size dummy primary mirror and support assembly was successfully reviewed in September 2020.
Slow-motion side impact testing of TMT Primary Mirror Assembly Shipping Container (PMASC) at Larson Packaging Company, September 2020 - Significant violent crash impacts of four meters per second were conducted and demonstrated the level of protection for TMT’s extremely fragile equipment. Shock loads on the SSA and PMA did not exceed maximum allowable values - Video credit: TMT International Observatory
Still, the shipping container will not only protect TMT’s polished mirror and support structure from acceleration events and shocks, but also from dust and splashing water. Data loggers with extra-long battery life will be mounted into the container and on the segment to monitor and record shock amplitude, temperature, and humidity of the environment during transport and storage. The container will also include a reusable moisture and anti-corrosion barrier bag made of Intercept fabric to seal and protect its content from the environment, especially during overseas shipments. The placement of the SSA and PMA into the bag will prevent the corrosion process and help keep parts clean, dry and ready for use upon removal from the packaging.
“This was a very interesting and challenging project for us, and allowed us to both demonstrate--and extend--our capabilities,” said Mark Hoffman, CEO of Larson Packaging Company. “I’m glad we were able to work collaboratively and closely together with TMT to successfully design, prototype and test a unique packaging solution for a sensitive and valuable system. This product helps the TMT project moving forward, and we will be thrilled to see the telescope get built.”
TMT Primary Mirror Assembly Shipping Container, India - First TMT M1 segment and new custom design shipping container arrived at ITCC facility in Bengaluru, India in early 2021 - Image credit: TMT international Observatory / India TMT
Larson Packaging Company has so far manufactured six complete prototype containers that can be shipped to partners’ locations. Two of them have already been used in real-life shipping environments and arrived successfully at the TMT partners.