Swimming With Astronauts Off The Florida Keys

Sea Technology, Dec 2006 by McLay, Scott, Cooper, Craig

Both Astronauts and Divers Experience the Benefits of a Cabled Umbilical

With so little yet known about space, mankind continues in its pursuit to better understand the iineharted areas of the solar system. The issues of exploring the vast frontiers of space have prompted astronauts to train in an environment much closer to home-the sea.

Future exploration of space requires a greater understanding of the limitations of the human performance when exposed to the challenges of this exclusive environment. Furthermore, limited experiences of vital procedures undertaken in space, and the extreme cost of space launches, have undoubtedly presented unique problems for enterprising astronauts. Thus, astronauts have turned to the ocean depths in their attempts to familiarize themselves with the complexities of space.

Indeed, the ocean depths are still far from fully understood. However, astronauts do not have to go to extremely deep waters to replicate the conditions of space travel. At depths of only around 50 feet, they can fully familiarize themselves with the comparable affects they can expect to experience at 100 kilometers above the Earth. This is a true testimony to the skills that commercial and sport divers have, many of whom work daily in depths well in excess of 50 feet.

Divers are very aware of the diffieulties of moving underwater and the iniluence this has on their center of gravity (CG). These environmental conditions underwater can he used to the advantage of astronauts, allowing them to replicate the CG found in space. With the development of a special CG backpack. acquanauts are able to familiarize themselves during sea walks with the various effects space has on their CG.

The reconfigurable CG backpack is designed to be used while the aquanauts carry out underwater experiments and get acquainted with the different gravity levels they would experience on the moon, on Mars or while on the International Space Station (ISS).

The moon has a gravity one-sixth of that of the Earth. Mars has a gravity three-eighths of that of the Earth. The difference in gravitational forces critically influences the astronauts' CG. Apollo moon walks demonstrated that the CG of the space suit and portable life-support system backpack had a crucial affect on astronaut performance. Preparing astronauts for the effects of this change in their CG is essential if space exploration is to continue in an effective and efficient manner.

Aquarius Habitat

In 1992, the National Oceanic and Atmospheric Administration (NOAA) Undersea Research Center (NURC) at the University of North Carolina, Wilmington, completed the refurbishment of Aquarius, an underwater ocean laboratory, deploying it at Conch Reef in the Florida Keys National Marine Sanctuary. Owned by NOAA and operated by NURC at the university in Wilmington, Aquarius provides scientists with the world's only remaining underwater experimental habitat.

The habitat has the capacity to support a six-person crew, with approximately 400 square feet of living and laboratory space. Contact to the surface is made possible via an umbilical linking Aquarius to a life-support buoy that in turn relays information through wireless telemetry to a land-based support station. The gravitational training undertaken by astronauts at the facility is primarily in preparation for future space missions.

Umbilical Design

Originally known as Diveline, Umbilicals International (UI) recently supplied the NURC team with newly improved life-support umbilicals, allowing less obtrusive tethered excursions to be carried out from Aquarius. These umbilieals allow astronauts to navigate effortlessly throughout the reef on excursions out to the full 400-foot length of the umbilical. The spirally wound umbilicals were selected in preference over the conventional straight-laid and strapped type of umbilical because their near-neutral buoyancy and construction minimizes the potential of snagging on the coral reefs found in the surrounding water at the training facility.

The traditional solution to combining these different elements is to lay out a rubber hydraulic hose, an air tool line, a military surplus cable and a length of poly rope, then strap them all together with copious amounts of duct tape every foot or so. So, how does this traditional umbilical actually perform in the field? The answer is that it works, but barely.

It is heavy (in air and water), hard to handle (for diver and tender), apt to throw loops and snag, and generally fails prematurely. The cabled (or ropelike) umbilical using purpose-built components rather than military surplus and industrial hose offers a superior solution.

These umbilicals are specifically designed for the undersesa application. Like a rope, the individual elements are spiraled around each other, allowing them to adjust their relative positions during bending to eliminate stress build-up due to differential lengths.

With a spirally wound umbilical, no one component sees excessive compression or tension and, therefore, is much less likely to be considerably damaged, increasing the life of the product. In addition to the cost savings of reduced maintenance and extended life, cabled umbilicals made from purpose-designed components offer very significant user benefits over traditional solutions: being kink-resistant, smaller, more flexible and lighter (both in air and water).