Andrew Roberts,
WB-57 Program Manager,
NASA’s Johnson Space Center, Houston, TX

When the Space Shuttle Discovery (STS-114) returned to flight in July, a pair of NASA WB-57 chase jets that provided extra “eyes in the sky” escorted the shuttle to watch its flight and help safeguard its crew. The jets carried innovative, on-board video imaging systems, dubbed the WB-57 Ascent Video Experiment (WAVE), that captured detailed images of how the space shuttle behaved as it climbed toward orbit. Andrew Roberts is the program manager of the WAVE project.

NASA Tech Briefs: What is the WB-57 Ascent Video Experiment (WAVE)?

Andrew Roberts:  The experiment came out of the Columbia Accident Investigation Board (CAIB) results. One of the board’s recommendations was to have airborne or sea-born imagery of the shuttle during launch. In the past, we had flown a system called Skyball on our WB-57, which was the chase airplane for the Global Hawk aircraft. We had a small 15” ball that we had on the airplane used to track the Global Hawk. So we went to NASA management and suggested that we could quickly press this into service for the shuttle.

Bob Page, who is the head of the Inter-Center Photography Working Group at JSC, which is in charge of all of the HDTV imagery for the agency, had some very specific requirements. He wanted everything to be HDTV, and he wanted much better resolution than the system we had previously flown had been able to support. What we discovered was that nobody had anything in existence that could do the job. As a result, we proposed the WAVE system with a 32” ball that we put on the nose. In that ball we have both HDTV and infrared cameras that work off the same telescope, which has a 4.2-meter focal length and an 11”-diameter optic on it. We also have a third camera – the acquisition camera – that has a much larger field of view. The telescope, or the HDTV and infrared cameras, have a field of view of about 1/10 of a degree, which makes it rather difficult to spot something in the sky looking through a hole the size of a soda straw. With the acquisition camera, we can lock onto the vehicle and move the HDTV to the correct position.

NTB: Was the launch viewed in real time? 

Roberts: There was no real-time imagery being broadcast from the aircraft – it was all post-process. There are many issues with emitting electromagnetic radiation around the shuttle. There is so much of it that anyone who wants to add one more frequency would have to go through a major review and analysis process to be allowed to emit in that area.

One thing of value from the IR camera was the reentry work. Initially, the reentry purpose was mainly to benchmark what a normal reentry looked like. A second purpose – developed during the year we were building it – came from a team at Langley that does aerothermal analyses. There is a big concern about when the boundary layer of the shuttle, during reentry, goes from laminar flow to turbulent flow. The reason this is important is because there is about a 300°C increase in the temperature of the vehicle. They have a process where they analyze that and make a determination when that occurs, and one of the things they wanted us to do was to validate it. Since we had the IR system on board, a prime capability for us was to see that change in temperature when it occured.

NTB: Was the imagery obtained useful?

Roberts: There were several firsts that we ended up with. One surprise was that the foam on top of the external tank, which they always knew to change color and heat up during the launch process when it gets up to high enough Mach numbers, occurred much earlier then previously believed. We were the first people to capture that view of the top of the tank. The other big surprise, which was never really part of the plan, was that when the shuttle was passing some clouds we were able to see all of the shock waves coming off of the shuttle due to the way our folded optics worked on the WAVE sensor. That was really very impressive – you could actually see the shock waves coning down as the Mach number was increasing. The aerodynamicists are now taking that data and comparing it to the wind tunnel data that they’ve had for years. In the wind tunnel you get reflections of shock waves, while our system was able to determine the real situation.

NTB: Will NASA continue to utilize this technology in future space flight missions?

Roberts: The experiment has been funded to go through the first two launches and catch the first five entries. Following the two missions, we’re going to take a look at it and decide if we want to turn it into an operational system.

NTB: Are there commercial applications for the WAVE Technology?

Roberts: There have been many calls that have mostly come from within the government. For example, we’re going to try and catch the Stardust spacecraft’s return next January. The Missile Defense Agency (MDA) has requested that we track some bad missile launches out of Hawaii, and the Department of Homeland Security also is interested in looking at our system. So it’s mostly governmental-type programs outside of what NASA developed, but there has been a lot of interest from many different organizations to potentially utilize this system.

As for commercial businesses, especially since we were able to see the shock waves come off of the vehicle, if someone is trying to develop, for example, scramjet, hypersonic, or supersonic aircraft, this may be a line of work where we could validate the wind tunnel work or find things that the wind tunnel did not catch.

For more information, contact Andrew Roberts at andrew.c.roberts@nasa.gov.