By Bob Granath
NASA John F. Kennedy Space Center
Preparations for the launch of NASA’s new Orion spacecraft recently took an important step forward. A prototype seal for the launch tower’s crew access arm, or CAA, was successfully tested at the Kennedy Space Center’s Launch Equipment Test Facility in Florida.
The simulation evaluated the new technology used in the design and function of the inflatable seal. The assessment team used mockups of Orion’s outer mold line and the access arm White Room to evaluate the performance of the seal while simulating vehicle to CAA work.
The testing went very well and proved the concept works,” said Kent Batchelor, a senior mechanical engineer with Stinger Ghaffarian Technologies, Inc., (SGT) working under the space agency’s Engineering Services Contract.
“We want to do the best we can to protect the hatch area of Orion,” he said. “The seal will give us a water-tight connection between the White Room and the spacecraft.”
The Orion spacecraft is designed to take crews of up to four astronauts on missions to deep space including asteroids and, eventually, Mars. The initial Orion launch will be atop a United Launch Alliance Delta IV rocket. Later the spacecraft will be sent beyond low Earth orbit by NASA’s Space Launch System.
For either rocket, the crew access arm attaches to Orion near the top of the launch umbilical tower. At the end is a box-like clean room that moves to within inches of the crew module’s hatch.
Prior to flight, the CAA and White Room provide technicians access to the Orion spacecraft. On launch day, the flight crew will ascend the launch tower’s elevator and walk across the access arm to enter the Orion from the White Room.
While this is the same concept used for Apollo and the space shuttle, the inflatable seal is an innovation. The final inches between the White Room and the Orion will be filled by the tube-like seal pressing against the spacecraft.
“The shuttle had a low-pressure, inflatable Herculite seal covering the last few inches between the crew access arm and the orbiter,” said Batchelor, who was the seal testing lead for SGT. “It was assisted by an over-pressure inside the White Room. For Orion, the inflatable seal is an advancement over Apollo and the shuttle. That seal is designed to fit tightly enough to prevent dust, debris or even insects from getting in.”
A White Room mockup structure was designed and fabricated to hold the prototype seal in place. The White Room, with the seal attached, was fixed on a pedestal next to the vehicle motion simulator (VMS). The Orion outer mold line then was attached to the VMS at the Launch Equipment Test Facility.
Design of the seal and preparations for the test have been ongoing for the past few months. Confirmation that the design would, in fact, work came on Nov. 14.
“We originally planned for the test to stretch over two days,” Batchelor said, “but it went so well, we completed the task in one.”
The assessment included ensuring the seal did not press too hard against Orion. The pressure is designed to be firm enough to keep rain-water out, but only press from 0.15 to 0.3 pounds per square inch.
“We want to protect the Orion, but we don’t want to damage it either,” Batchelor said.
Protection against Florida’s typical weather is another concern. Wind can cause the launch vehicle to move from side to side. Dynamic testing with the VMS demonstrated that the launch vehicle could sway up to eight inches in and out and 16 inches from side to side with the seal remaining in place.
“While the CAA should be rock solid, the launch vehicle may move slightly on Florida’s windy days,” he said. “The seal fit well against the simulated Orion exterior and kept out water that was sprayed from above to simulate rain. This was a good demonstration that the access arm seal can stand up to wind and rain while continuing to protect Orion and keep the White Room clean.”
Batchelor pointed out that testing showed some minor design changes will be necessary.
“During some of the tests, the seal collapsed improperly, but it looks like a few changes should take care of that,” he said.
Ultimately, the verification testing showed the innovative concept works.
“I’m very proud of the team,” Batchelor said. “Overall, our checks verified that the seal will not damage the spacecraft and can provide the needed protection.”