Trial by Water

“When we decided we were going to do a water landing,” said Alan Rhodes, part of the Orion test and verification team at NASA’s Johnson Space Center, “we sat down and looked at all the different things we needed to review, all the things we hadn’t done with this new design.”

For starters, the engineers at Carderock built a 1/10-scale model to verify the flooding potential of the full-scale model. “It’s a long way to go from a computer to a physical object,” explains Mark Melendez, a mechanical engineer and solid modeling expert at Carderock. And the engineers wanted to see whether their test article would flood.

Lockheed Martin sent Melendez three different models of Orion, from various stages of the design cycle. Using stereolithography (a fabrication process using a liquid resin and a laser to build parts one layer at a time), Melendez constructed a see-through 1/10-scale model.

“All of the detail that’s inside the full-scale model,” says Todd Carrico, Carderock's lead test engineer on the project, “is in the 1/10-scale model. And because of the nature of the material—it’s transparent—we could see the flooding potential very easily.”

Next, a quarter-scale model was developed by a team at NASA’s Johnson Space Center (JSC), and taken to Carderock for testing.

The quarter-scale experiment had two goals. “The first was to determine the optimum towing configuration of the capsule,” said Carrico. “We also looked at the equipment that would be installed post-splashdown,” such as a sea anchor and flotation collar, that will help the search-and-rescue teams to retrieve the astronauts (and recover the capsule) more quickly.

The quarter-scale model was tested for the best possible towing configuration in Carderock’s tow tanks, which are normally used to test ships, submarines and unmanned vehicles. Then they were taken to the outdoor wave pond at the U.S. Army’s Aberdeen Proving Grounds in Maryland, where the engineers tested it in Sea States 3 (a sea wave with a significant wave height of about three feet) through 6 (a wave height of at least 16 feet). “On average,” says Carrico, “those waves are taller than the capsule. It was pretty dramatic. It would be lost as it would go down into the troughs of the waves, and then reappear back on the crest.” The results allow NASA to predict the behavior of the capsule—and gauge how rough seas will affect returning astronauts.

“We got a first-hand look at what it takes to tow the capsule,” said Richard Banko, the lead engineer and construction manager at Carderock. “If the weather is bad enough, and the recovery ship isn’t close by, any ship of opportunity can tow the capsule into sheltered waters.”

When the Orion crew capsule design was originally given to Carderock, the heat shield was to be made of PICA (Phenolic Impregnated Carbon Ablator) material. (NASA has since chosen the Avcoat ablator system that was used on Apollo capsules.) “Our heat shield,” says Carrico, “obviously isn’t PICA. But it serves the same function in terms of weight distribution. That’s all it has to do. This is not a flight article, this is just for at-sea testing. So we’ve simulated the weight of the PICA, but we’ve taken it a step further because the PICA saturates”—which adds significantly to the weight of the capsule.

“The point of the full-scale article,” says Carrico, “is attention to detail. Not only the detail on the outside that you can see, but there’s a lot of effort on the inside to make this the most high-fidelity test article in the whole [Constellation] program.”

The Orion spacecraft will seat six people—twice as many as fit in the Apollo capsule. “The Space Station today only has three people on it,” continues Pearson, “but we hope to build it up to six people within a year. And then, if there’s an emergency, we’d like to be able to put all six in one capsule. Another reason it’s bigger, is that when we go to the moon, we want to send four people instead of three. And this time all four people will go down [to the lunar surface].”

“A lot of the time,” says NASA’s Alan Rhodes, “people will ask ‘Well, you did this in Apollo, you don’t need to worry about this.’ But this is a completely new vehicle, it’s much larger, and the added space will affect how it’s going to float on the water and react to the waves.”

Parajumpers from Air Force Special Operations Command were at Carderock to get practice adding the floatation collar and sea anchor during a night dive. The decals on the capsule show the divers the locations of windows and thrusters that will be exposed to the water.

“If there’s a problem, and that capsule lands somewhere in the world between 51.6 [degrees] North and South, [NASA] wants to know that we can rescue the astronauts in 24 hours or less, which is a huge challenge,” says Commander Andy Quiett, of the Department of Defense, who leads NASA’s launch and recovery group. The DoD is responsible for handling recovery contingencies from launch until the Orion capsule is docked to the International Space Station—a span of two or three days. The DoD team would have two Zodiac boats loaded with equipment (such as the flotation collar and the sea anchor) on a 24-hour alert, able to launch with an hour’s notice. Rescuers would carry a small bottle on their leg with a 30-minute supply of air, although, says Quiett, “We don’t know right now how long it will be before the capsule is determined safe.”

After the Orion full-scale model left Maryland, it spent a day on the National Mall, parked in front of the National Air and Space Museum, before heading to NASA’s Kennedy Space Center in Florida for two weeks of at-sea testing.