Mobile launcher gets Orion crew access arm, inches closer to completion
KENNEDY SPACE CENTER, Fla. — Workers with NASA’s Exploration Ground Systems at Kennedy Space Center (KSC) recently passed another landmark in their effort to prepare the center’s infrastructure for the maiden launch of the Space Launch System (SLS). Secured to its perch at the 274-foot (83.5-meter) level, the installation of the crew access arm marks the latest item to be crossed off the list as NASA moves toward the launch of SLS on Exploration Mission 1 (EM-1), officially targeting liftoff in late 2019.
The crew access arm was manufactured at nearby Precision Fabricating and Cleaning in Cocoa, Florida. It consists of a truss assembly as well as an environmental enclosure—colloquially known as the “white room”—and is one of twenty major components to be installed on the 380-foot (115.8-meter) tall mobile launcher.
To date, 17 of the 20 major connection elements have been installed on the tower, with only the Interim Cryogenic Propulsion Stage Umbilical and two Tail Service Mast Umbilicals left to be installed.
The crew access arm will allow astronauts to board the Orion spacecraft as it awaits launch at KSC’s historic Launch Pad 39B. The arm will retract before launch to allow for a clear ascent from the pad. Although EM-1 will launch without a crew, the access arm will provide workers access to the Orion spacecraft for equipment loading and checkout.
Once workers complete the installation and assembly of the remaining components, the mobile launcher will be transported out to Pad 39B for fit-checks. Following the launch site validation work, the launcher will be ferried back to the Vehicle Assembly Building (VAB) atop the upgraded Crawler Transporter for further verification tests.
Reports of leaning
The launcher’s tall steel tower, rising from the Mobile Launch Platform, has been the subject of concern for some. It was reported by NASASpaceflight that the tower is leaning in a direction that would tilt it toward the launch vehicle. However, some at NASA have contradicted this and similar reports.
“The mobile launch platform is not leaning and it is built within the standard steel design and construction codes,” said Darrel Foster, NASA’s chief project manager of exploration ground systems.
Ars Technica issued a report by Eric Berger that stated the tower would only be used once and that it leans. Foster’s comments also appear to contradict Berger’s article.
“We are planning on using this for more than just EM-1, for EM-2. Our plan is to modify [the launcher], in fact we’ve already started design efforts to modify it,” Foster said. “Right now we’re planning on modifying this and reuse it and that’s our plan for the foreseeable future.”
NASASpaceFlight reported last week that not only was the ML leaning (to the north) but that it was also bending, citing “notes” and that engineers were concerned about this issue, prompting delays in further access arm installations. NASA told NSF’s Phillip Stoss, who asked the space agency for clarification on the issue, that the ML bending/leaning wasn’t the cause of the delays involving the installation of the crew access arm.
“The measurements we’ve done on it, for a tower this size, it is very straight and it is within the steel code tolerances that they lay out…,” Foster went on to say, noting that he is comfortable with the ML’s status. “It does not keep me up at night.”
Foster said the platform, which cost almost $1 billion to build (according to a report appearing on Popular Mechanics), could be used for more than the first and second flights (Exploration Missions 1 and 2) of NASA’s SLS, but did not know how many launch cycles the ML would be able to support. This would appear to contradict Avery Thompson’s report in Popular Mechanics which states that, “It’s unlikely the giant structure will be used for more than a single launch.”
According to Foster, while NASA has considered producing more than one ML for use with SLS, at present the plan is to use it for multiple flights of the massive new rocket.
“We have looked at some plans for a second mobile launcher, because there are some advantages, and there are some disadvantages too,” Foster said. “Like any other trade study that we do within NASA, we look at all of the pros and cons, we look at the cost benefit, we trade the technical risk, the cost risk, the schedule risk … we take all of that into account. Right now, our current plan is to modify this one. Yes, we are looking at it, It has been talked about, but we have not made any decisions on that.”
Foster said the Block 1B version of SLS, which will be used for EM-2, is approximately 40 feet (12 meters) taller than earlier planned versions of the new rocket.
For now, NASA states that the tower was designed to handle the loads being placed on it and it is behaving as expected. According to an agency release:
“Similar to skyscrapers and other large structures, engineers designed the mobile launcher to withstand the movements associated with predicted loads and compensate for anticipated forces. As each piece of hardware is installed, teams precisely measure the structure to ensure the required alignment of the swing arms and umbilicals with the vehicle interface are within the design tolerances.”
The agency expects workers to complete the umbilical assemblies on the launch tower by the end of the Summer of 2018. The mobile launcher should be rolled into the VAB for the first time during this period.
“One of the things that we’re doing right now, I like to call the virtual fit check,” Foster told members of the media including SpaceFlight Insider during a recent interview session at KSC. “What we’re doing is taking highly-precise survey measurements of the mobile launcher, the VAB and out at the pad to make sure that everything lines up when we put them together.”
Video courtesy of NASA
Curt Godwin has been a fan of space exploration for as long as he can remember, keeping his eyes to the skies from an early age. Initially majoring in Nuclear Engineering, Curt later decided that computers would be a more interesting - and safer - career field. He's worked in education technology for more than 20 years, and has been published in industry and peer journals, and is a respected authority on wireless network engineering. Throughout this period of his life, he maintained his love for all things space and has written about his experiences at a variety of NASA events, both on his personal blog and as a freelance media representative.