By Aerik Carlton
While working with private space industry clients on launch complex structures, we have found some notable structural challenges. This article is meant to share some of Nishkian Dean’s recent launch site design experience. Specifically, an atypical structural load consideration that was identified and requested to be evaluated by our client.
Recently, launch tower structures, designed by others, near one of our project sites had been found to present weld failures at circular structural member support connections. The design and construction team that completed the nearby tower believed the weld failures to be representative of “bad welds” during construction. This conclusion was drawn because there appeared to be random failure locations. The failed connections were rewelded, but the repaired welds were found to have failed at the same locations in a follow-up inspection.
Aerospace is one of the most remarkable market segments in which the Nishkian firms have been privileged to contribute their engineering expertise. Nishkian Dean VP and Managing Principal, Edwin T. Dean, designed rocket launch facility infrastructure prior to founding Nishkian Dean in 1999 and, since then, this small firm in Portland, Oregon, has designed or assisted in the construction of some major aerospace projects throughout the United States. During this same time, the aerospace industry has transformed from a large institutionally-focused bureaucratic process to one that has embraced commercial innovation.
There are many things to take into account when designing and operating cryogenic systems. Possibly the most important consideration is the extreme temperature ranges involved. Two of the most commonly used propellants (rocket fuels) are liquid oxygen (LO2) and liquid hydrogen (LH2). The boiling point of LO2 is 297 degrees below zero Fahrenheit, while LH2 boils at -423 degrees Fahrenheit. Moving these super-cold liquids from Point A (likely, a storage tank) to Point B (a rocket or shuttle) requires a great deal of careful engineering.
For example, a 100 foot-long section of stainless steel pipe, exposed to super-cold LO2 temperatures, will shrink about four inches in length. Although this may not seem like much of a difference, it equates to thousands of pounds per square inch of stress on the piping. If the pipe section is rigidly restrained, the stress forces could cause pipe supports to fail, welds to crack, and rocket fuel to leak from the piping.
The solution is to design cryogenic systems with enough flexibility that the piping is allowed to contract and expand as necessary. This is commonly accomplished through the use of expansion loops (see Figure 1). These loops are essentially U-shaped pipe sections that allow for cryogenic piping to move and flex when necessary.
As 2015 began, the New Horizons spacecraft awoke from an extended hibernation period on its journey to Pluto and the Kuiper Belt. The spacecraft, currently in the ninth year of its trip, is nearing the outer fringe of our solar system and is documenting this previously unexplored area. It has flown over 3 billion miles so far and will conclude its planned mission after completing approximately 135 million more, sending images of Pluto and its’ moons 4.67 billion miles back to Earth. This monumental undertaking would have been postponed for years if not for the rapid response of support firms, including Nishkian Dean, in the late Fall of 2005.
On October 24, 2005, Hurricane Wilma, part of that year’s record breaking hurricane season, moved through the Yucatan Peninsula, into the Gulf of Mexico, eventually making first landfall on US soil in Cape Romano, Florida. The storm devastated the coast and blew through Cape Canaveral Air Force Station and SLC-41, causing catastrophic failure of a major potion of the 40’ wide by 280’ tall folding fabric door (Megadoor) on the vertical integration facility (VIF), which housed the launch vehicle for the New Horizons mission. This nearly resulted in an estimated three-year delay of NASA’s planned New Horizon’s launch.
The ending of the Shuttle program in 2011 meant that the US would no longer possess the capability to put men and women into space, making us completely reliant on other nations for transit to the International Space Station and destinations beyond. Although our team has the opportunity to work on many exciting projects every day, no challenge has been as exciting as our role in restoring US capabilities to support human space flight. On December 4, 2014, NASA’s Orion Exploration Flight Test 1 is scheduled to launch aboard a Delta IV Heavy off of Launch Complex 37 (LC-37) at Cape Canaveral Air Force Station. During the planning process for the upcoming launch, Orion’s preparations hit some complications that Nishkian Dean was excited to have a hand in repairing.
Orion is assembled in the Neil Armstrong, Operations and Checkout Building, commonly known as the O&C. Recently renamed after astronaut Neil Armstrong, the facilities heritage goes back to processing Apollo missions when it was first built in 1964. In 2012 the O&C was totally re-outfitted and restored to operational condition in order to support the assembly and future refurbishment of the Orion space capsule and Crew Service Module (CSM). Nishkian Dean took on an important role in the restoration when the Orion tooling and test fixtures proved to be far heavier than what the O&C floor was capable of supporting. Our team worked with Lockheed Martin Space Systems and Hensel Phelps to install an innovative pile underpinning system to permanently shore up the floor. The 140 piles were installed through the floor and bear on the heel of the basement retaining wall below, leaving only a 20-inch hole to patch in the clean-room environment of the O&C. The need to shore the floor was realized only late in the construction process so it was critical that a method be developed that wouldn’t damage existing construction, disrupt ongoing work, or contaminate the clean environment of the O&C. The solution proved to be efficient, keeping the O&C project on schedule, and Orion was successfully assembled and tested in the O&C then shipped out for the next step on its journey into space.