Marcia Domack and John Wagner, Engineers, NASA Langley Research Center, Hampton, VA
- Wednesday, 01 August 2012
Domack: It’s a well-established commercial capability to make a dome structure, which, if you look at it in cross-section, is a big arc-shaped component. We’re trying to extend this technology to the next level of development, and the next level of complexity. And if we’re successful at showing that we can make something this complex, we’re already, from a commercial standpoint, making a simple geometry and advancing this technology area, where we can make just about any shaped component that we need.
Wagner: Typically, in the work that we do, we look at both the innovative manufacturing, like the spin forming technique, but we also try to incorporate lightweight, advanced materials. The best of both worlds would be to be able to do this innovative technology, like this spin forming of the Orion crew module, and do it with a lighter weight material. The current material that we used for the demonstration article is an aluminum that has a designation of 2219 aluminum alloys, an alloy that has been around since the 1950s. There’s a more recent type of aluminum lithium alloy, alloy 2195, that’s about ten percent lighter, and ten percent or more stronger than some of the regular aluminum, like 2219. We don’t have as much experience with that material, so the next step we envision is to do this innovative forming with a lighter-weight aluminum lithium alloy.
Domack: In the long-term, the goal for a component like the Orion crew module would be to significantly reduce the weight in the vehicle and improve the performance, and do that by a combination of using this single-piece, spin-forming technology to get rid of the welds and the joints, and fabricate that from the aluminum lithium alloy. Either one by itself should gain us weight reduction in the vehicle, but when you combine the spin-forming technology with aluminum lithium, we feel like that weight reduction can be significant. Getting the weight down in the crew module allows us to add something inside, whether it’s additional personnel, like another astronaut, additional support systems for the crew module, or additional payloads.
NTB: Can you take us through that process of spin-forming a single-piece crew module?
Wagner: Originally, we’ve worked a suite of numerous near-net-shape technologies, and in the beginning, most of those were pretty standard: cylinders, and rings for attaching domes to, say, cylindrical sections. We thought that the next step would be: Could we do something that’s close to near net, using any kind of forming technology or spin-forming or flow-forming, but do it in a cone or conical section? Originally, we were trying to make a transition from straight cylindrical sections like you would have on a barrel section of a propellant tank, and a conical section like you might see in a transition region between two stages on a rocket, where it has a big diameter or small diameter. We took that idea to several companies, and we settled on trying to do that by spin forming. During the discussions with our technical colleagues at Spincraft, we mentioned almost in a joking manner, “It’d be nice ultimately, to be able to make a whole Orion crew module by spin forming this technology.” And after we examined that further, we determined that it wouldn’t be that big of push, technology-wise, to do either a conical section, or just go for broke or try to do the whole crew module that we were successful in doing?
NTB: Are there any hang-ups? Why would someone hesitate to use this method?
Wagner: One thing that we’ve found in some of the launch vehicle and aircraft industries is the mentality, and rightfully so, of “If it ain’t broke, don’t change it.” If it works well, why introduce the variable of new technology? There’s got to be a real driver for the new technology to earn its way on to either a rocket or an airplane.
Domack: The next step in our work is to quantify just how much of a benefit this kind of a single-piece construction can be over what the Orion now uses, and the many-piece, multi-piece welded construction.
NTB: Are there any other big design challenges when spin-forming?
Domack: Not so much with spin forming, but with an article like this, there’s a lot of hesitation, once a manufacturing path is established, to insert new technology, particularly technologies that significantly change how things are done. One thing we will have to address with single-piece construction is how you would add other systems to it. There are other things that have to attach to this forward pressure vessel bulkhead. If you look at the Orion crew module, or other crew capsules that are being developed, there’s a nice, smooth outer mold-line that’s on an angle. Obviously inside that, there are many systems. There are parachute systems. There are all kinds of support systems. Within all of that is a pressure vessel that the astronauts ride in. What we are making is that underlying structure. So we are planning to work on an upcoming project with the designers of all those systems. With multi-pieces: as they’re welding two pieces together, they can add in an extra flange. We’ll have to work with them to design how they would make those additions to our bulkhead.
NTB: Can you talk a bit about the partnerships that you’ve formed as you’ve been going through this spin-forming process?
Wagner: We’ve been partnered very closely initially with Lockheed Martin Michoud Assembly Facility, which is outside of New Orleans. NASA and Lockheed Martin Corporate have a Space Act Agreement that allows for the exchange of information and material and ideas between these two companies. The Space Act has been very instrumental in providing a vehicle with which we can work with our colleagues in private industry. Also, we have been working with the people who did the actual spin forming, which is Spincraft in North Billerica, MA. Marcia Domack, in particular, worked with them on a spun-form dome project a couple years ago, under the NASA Exploration Technology Development program.