Orion configuration considerations
“The thing that kept me up at night just gagging was the prospect of needing to shift twenty-five metric tons three kilometers per second out of low Earth orbit into trans-lunar injection,” Wood said. At the outset, one of the things the study group looked at was how they might reduce Orion’s mass to make it better fit one of their launcher options.
The twenty-five metric tons is the approximate in-space mass of Orion; however, the spacecraft launches with a massive, tractor rocket abort system that also serves as an aerodynamic fairing.
“The Launch Abort System and what they call the ogive shroud, those were items that I wanted to attack immediately because between the LAS and the ogive shroud and the tri-sector cylindrical aerofairing that’s ejected from around the Service Module in flight after dynamic pressure falls off, that was a lot of mass, that was on the order of twenty-thousand pounds mass or approaching ten metric tons on its own,” Wood noted.
“Not only is it mass that we think we didn’t need in flight — obviously we weren’t going to be jettisoning the capsule — but also that was a lot of additional mass to simply have to handle in the ground integration.”
The Orion Launch Abort System (LAS) covers the Crew Module (CM) during the early part of launch ascent. Credit: NASA.
Setting aside crew safety, since EM-1 is an uncrewed launch and mission, flying Orion inside a standard payload fairing might have released those ten extra metric tons of launch mass. “[The goal] would have been keeping them within the static envelope that’s allowable either by the SpaceX five-meter fairing that flies on Falcon or the five-meter ULA fairing,” Wood said.
“They have specific static envelopes that are allowable that constrain you both in diameter as well as axial station and so that would have been the limiting factor and it would not have fit.”
As they dug deeper into the problem, consulting with Orion’s prime contractor Lockheed Martin, they came full circle. “When we looked at their system-level impact they needed the LAS to get the ogive fairing off of the command module (Orion crew module), they couldn’t just fly the command module without some kind of fairing,” Wood explained.
“We weren’t going to be able to fit the command module and that stack inside of a conventional payload fairing that we would have to bring to bear on either Falcon Heavy or the Delta 4 Heavy, so we said really we need to leave the LAS in place and we need the LAS to get the ogive fairing off. We can jettison it earlier in the flight than it would be for a crewed mission, but we pretty much have to leave it on there.”
“And then the aerodynamicists came back; our aerodynamicists did a preliminary look at what buffeting considerations we would have to look at,” he continued. “For example EFT-1 (Exploration Flight Test-1) flew with the Orion outer mold line integrated into a five-meter core on a Delta 4 Heavy, but on a Falcon Heavy that’s a less than four meter diameter core and so you’re talking about having a hammerhead configuration aerodynamically and we would have to look at that as to whether or not we were going to be inducing aerodynamic buffet considerations.”
“So from an aerodynamic standpoint it also made the most sense to leave the LAS in place and that hurt because I really wanted to get rid of that thing, but it made sense,” Wood continued.
The EFT-1 Orion as it was mated to the Delta 4 Heavy launch vehicle in November, 2014. Credit: NASA/Radislav Sinyak.
“From the standpoint of initial consideration going in I think the spacecraft customer would have wanted us to leave it in as a ground rule. In challenging that ground rule and challenging what we could do with it and what benefit we could take from it we worked our way around back to say, you know, it’s not really worth chasing this, we’re not going to get enough benefit out of the deal.”
Orion mass reductions and docking additions
In-space mass was also going to be an issue, and the Orion crew module was going to need to be stripped of any non-essential items for performance reasons. “We stressed the Lockheed Martin and the Orion folks quite a bit, and I say that positively but we definitely pushed them outside their comfort zone with our requests to investigate what they might do to shed mass on the command module and on their stack,” Wood said.
“Of course realize, most of the EM-1 spacecraft stack is built and the command module is closed out. So we can blindly talk about removing mass simulators and say ‘hey that would save us over a thousand pounds of dead weight that we don’t have to push into trans-lunar injection any more.’ And they said ‘yeah, but we’re the ones that have to do it, our command module is buttoned up.'”
“These things are not sitting out there saying ‘hey take me I’m a mass simulator and unload me off of the capsule,'” he continued. “That was going to take quite a bit of work on their part.”
“They did work it out how they would approach the problem and do it and then we would also work with them on ideas of different fuel, partial fuel loading options on the European Service Module and tried to explore every bit of the trade space that they had available to them from the Europeans and from their own requirements for being able to vary the amount of propellant that was loaded on there.”
The public debut of the feasibility study was accompanied by the suggestion of doing a dual-launch, Earth Orbit Rendezvous style mission, so rendezvous and docking options were another avenue studied at the outset.
“Before the performance answers would even start to favor or not favor a rendezvous solution one of the things we needed to establish, and this was working with the JSC Orion project office and Lockheed Martin the prime contractor, was on the Orion side whether or not they would even have a capability for a rendezvous and docking of another vehicle, should another vehicle become available or be created to apply the delta-V to the stack to finish getting it out to the trans-lunar injection,” Wood explained.
A Lockheed Martin technician looks at the EM-1 Crew Module hatch in the Operations and Checkout Building at Kennedy Space Center in March. Credit: NASA/Ben Smegelsky.
“The EM-1 mission configuration does not have a docking collar, nor the software and avionics to accomplish a rendezvous on its own. So one of the things that we did early on was investigate with Orion and Lockheed Martin the feasibility of being able to integrate a docking collar and associated hardware into the command module on EM-1 such that we could accomplish a rendezvous with their spacecraft in what was called a passive-passive mode.”
“And that is to say not try to accelerate the docking capability but rather allow the capsule to just be a passive target and let someone else like a Dragon based vehicle accomplish the rendezvous as the active participant with the active docking collar, something like what was accomplished when the Dragon DM-1 mission flew to the Space Station and it accomplished an automated docking there,” Wood continued.
“That was an area where Lockheed Martin and JSC Orion put in some serious effort to be able to characterize, identify the hardware, the schedules, the timelines that would be necessary in order to put a docking collar onto the EM-1 Orion and be able to facilitate that kind of in orbit rendezvous.”
“In parallel we worked with SpaceX, because of course they’re the only ones with a flight-demonstrated autonomous rendezvous capability and so I spent some time with their Dragon GN&C (Guidance Navigation and Control) folks out in Hawthorne, we spent some good bit of time on the phone discussing the specifics of what that system needed, what its capabilities were for rendezvousing with a passive target with just optical targets and laser reflectors on it.”
“That was one of the crucial enabling technical elements to say ‘is rendezvous even in the picture?’ Now ultimately from a performance standpoint, there was no rendezvous option that bore any fruit that we could realize in the short design and integration timeline that we had available and the reason for that is just that even if I had an Orion stack in orbit that had a docking collar on it that could accept a docking from an active participant, shifting that amount of mass out into trans-lunar injection from low Earth orbit was just such a Herculean task there’s nothing on the shelf today that would accomplish that.”
“Essentially, a new stage would have to be designed around Dragon’s rendezvous/docking and propulsion elements,” they added in a follow-up email. “Certainly keeping the Falcon second stage attached to Dragon would have been an option to meet performance requirements, but as indicated during our initial interview, the thrust generated by the SpaceX Mvac engine produces loads that are not acceptable to this payload, so this option was quickly ruled out.”
Horizontal integration
Another area that was tackled at the beginning was integrating Orion with the SpaceX Falcon Heavy launch vehicle — Orion was designed for vertical integration, Falcon for horizontal integration. “That was one of the things that we attacked right away, knowing that Falcon Heavy was a candidate and there was a potential that the horizontal integration could render that option infeasible right off the bat,” Wood explained.
“So that was when we worked directly with the Lockheed Martin spacecraft team who, as it happens is down here in the same building that we are, and so I kind of short-circuited the process just a bit and worked with a couple of their senior engineers. In the course of two or three days we worked through the problems and the challenges that would be associated with integrating the spacecraft in the horizontal.”
Falcon Heavy with the Arabsat-6A communications satellite is raised from horizontal to vertical at Launch Pad 39A on April 10. Launch-ready Falcon payloads are mated horizontally in the Horizontal Integration Facility at the pad. Credit: Brady Kenniston for NSF/L2.
“When the spacecraft goes up to Plum Brook for their thermal vacuum testing, they’ll fly in the Super Guppy and they will fly in an unfueled, but horizontal configuration,” Wood continued.
“Now they won’t have the LAS on there, but the spacecraft can take some degree of horizontal handling and transport loads, but there’s quite a bit of propellant for a spacecraft in a launch configuration and of course you’ve got the heavy LAS that would be attached to the nose of the command module structurally and would have to be factored into whether or not you could accomplish a horizontal to vertical transition on the Transporter Erector necessary to launch a Falcon Heavy in the configuration that they have today.”
“We only made it far enough before the end of the study to be able to say that the team working the problem had found no obvious showstoppers, but that there was going to be a considerable amount of work that still had to be completed. And a lot of that would have involved coordination with the Europeans, because now we would be handling their Service Module in a fueled condition that’s not consistent with the vertical integration and vertical handling that they had planned for all along for their nominal processing here at Kennedy.”
“Again the enemy here is time, so if you’re going to do a short timeline for integration, currently they have no vertical integration capability at Complex 39 for a Falcon 9 single stick or a Falcon Heavy,” Wood added. “The National Reconnaissance Office and the U.S. Air Force have asked them to look at a vertical integration capability and so some design work has been done in that direction, but nothing would be ready in time to support integration and processing in mid-2020.”
The Orion Crew and Service Module Horizontal Transporter (CHT) with a low-fidelity Orion “short stack” goes through a fit check with NASA’s Super Guppy aircraft in March at the Shuttle Landing Facility at Kennedy Space Center. Credit: NASA/Kim Shiflett.
“Really the best option would have been to work through the problems and make the horizontal integration and normal Falcon Heavy style of erection, to make that work. That would have been the least risk option.”
The spacecraft will also need some set of ground services, but that was also not considered to be a showstopper. “We had expected that we would be required to accommodate a ground umbilical servicing, which would be [a] normal part of our mission design for any of our spacecraft customers, so that level of mission integration design work was something that we didn’t have time to go into and we had judged that that was not going to be a discriminator on whether we had a feasible solution to fly them on a commercial vehicle.”