Meet Nujoud Merancy, a senior lead engineer at Booz Allen, where she currently serves as the Mission Planning & Analysis Lead for NASA's Orion. She brings to NASA's mission more than six years of experience in Orion vehicle integration, systems integration, and performance analysis. She previously worked for seven years with Boeing on the International Space Station Guidance, Navigation, and Control team as a systems engineer. In that position she was responsible for real-time flight operations engineering, international partner integration, and software interface development.

This extremely talented engineer discussed Orion’s mission with me and how it will be executed. This article which will go into detail regarding the sequence of events as Merancy has determined for optimal thermal, electrical and maneuvering sequence steps to efficiently and safely guide Orion through its journey.

Nujoud Merancy’s group is Mission planning; that is, how Orion gets to where it is supposed to go knowing Orion’s capabilities, her team goes over the thermal and power profiles that they have, are the solar arrays sized correctly so that if they do a specific “burn” do they have to turn equipment off to balance the power. They do all the power and thermal management; the Con ops—putting all the pieces together—the timeline. She interacts with the Flight Ops Division which will actually control things and her team needs to be sure that their expectations are being met. They supply all the integration pieces to put this together.

So when you take all of the electronics on board and turn them on, what has to be on, what is the redundancy management scheme, do they operate everything on? They have 4 computers—do they keep 4 on all the time or can they power down 2 of them when there is not much going on to conserve power or charge batteries faster—that’s systems management. Same thing with thermal, they need to be sure that the attitudes they are choosing provide the proper heat rejection from the radiators, as well as balance the solar demands for getting power on the solar arrays. It’s the trade-off between everything regarding how they are going to fly the vehicle.

When the astronauts exercise they actually produce a ton of heat so Merancy’s team has to balance that with other things going on too so they don’t plan for crew exercise at the same time a main engine burn is going on because those are both really high heat demand. They have to make sure that they schedule things appropriately and identify those constraints, so in general it is not good to stack all those heat loads on top of one another.

If the team does not work these things out, then the designers might not build the radiators large enough. They need to make sure that what they are building will meet their needs and then identify how they can operate within what they have built. Although the design is mostly there, it kind of goes back and forth but at this point they try to live with what they have but they need to work those things out. There was a great deal of analysis up front in the design of the arrays and radiators to make sure they were large enough.

NASA is now using the EFT-1 data to get ready for the next launch called EM-1. This will be a distant retrograde orbit of the Moon—about 70,000 km on the far side of the Moon. All the crew systems will not be on board for this mission since there are no people on the flight. EM-1 is the first full-up Orion with the European Service Module (ESM), the whole propulsion system and power system, all of the computer architecture. See Figure 1

Figure 1: Nujoud Merancy, Mission Planning and Analysis Lead for Orion in JSC Innovation Center

The distant retrograde orbit: “Distant” means we will not be very close to the Moon’s surface. “Retrograde” is in relation to the Moon’s travel—So if you are looking down onto the North Pole of the Earth, the Moon is traveling counter-clockwise around the Earth and Orion will travel clockwise around the Moon. See Figure 2 and this video link.

Figure 2: Orion’s EM-1 mission (Image courtesy Dan Dumbacher, NASA)

EM-2 is a design reference mission, adding the crew, and will go into a high lunar orbit or some other variations being discussed for the 2020/2021 timeframe. Now the Crew life support systems are tested, as well as the crew themselves with testing out more equipment and making sure that all the pieces come together to wring out the vehicle and get ready for exploration. We insert into a 100,000 by 10,000 km Lunar orbit—Merancy and her team are sizing the mission. It is designing the minimum thermal configurations, their ability to get in and out of Lunar orbit, but the actual mission is still being discussed. Right now they are using the high Lunar orbit as their design case. Between EM-1 and a Mars mission there will be many other interim flights including habitat modules and more. This is all a building-block approach to a Mars mission.

Figure 3: Orion’s EM-2 possible mission (Image courtesy Dan Dumbacher, NASA)

In the future NASA has plans to add things to Orion like a docking system, a sublimator or also known as Active Thermal Control System (ATCS) for the thermal system so that if they go into a low Lunar orbit they will need more heat rejection because the Moon can be hot. There are empty volumes and “scars” in place where they are keeping track of the things they need to add on in the future depending on what the mission is. Part of Merancy’s job is to make sure that they are capable of many missions but were not putting everything on the first time. Not every mission will need the same things so they have this building block vehicle. So depending on the flight you might add the docking system or a sublimator or extra water for example. See Figure 4.

Figure 4: Orion’s sublimator or Active Thermal Control System (ATCS). The two Interface Heat exchangers (IFHX) A and B are shown as part of two Command Module (CM) ATCS cooling loops and two Service Module (SM) ATCS cooling loops. The ATCS will control the crew environment inside the CM as well as maintaining the temperature of all avionics within their specified safety limits. (Image courtesy Reference 2)

When Orion returns to Earth it will take a direct entry there will be no getting into Earth orbit. They will come in at 25,000 miles per hour with temperatures rising to about 5,000 degrees Fahrenheit on the heat shield. It will be the highest entry return since the Apollo timeframe for a human-manned space vehicle. They will do a “skip entry” maneuver in which they will come in over the South Pacific but will land within a 10 km radius off the coast of San Diego. A “skip entry” means they are actually dipping into the atmosphere a little bit and then will use the aerodynamics of the CM alone to fly to a target location.

If you actually come right back, you can’t shape your trajectory a whole bunch. You can’t hit a precise 10 km entry point direct from the Moon at all times. What the “skip entry” does is allows them to make that precision landing so you only have to stage your recovery forces in one place. They will come in thousands of miles away and then use fly and guided entry to the right place. Apollo had the forces of the Navy and lots of resources that they could move around anywhere they wanted in the ocean. See Figure 5.

Figure 5: Skip Entry Maneuver Diagram. A Skip-Trajectory results if the vehicle leaves the sensible atmosphere and a second entry occurs downrange of the atmospheric exit point. The Orion capsule is required to have landing site access (either on land or in water) inside the Continental United States (CONUS) for lunar returns anytime during the lunar month. This requirement means the vehicle must be capable of flying ranges of at least 5500 nm. For the L/D of the vehicle, this is only possible with the use of a guided Skip-Trajectory. A skip entry guidance algorithm is necessary to achieve this requirement. (Image courtesy of Reference 3, 4)

EFT-1 Heat Shield performance

The EFT-1 flight also tested the integrity of the heat shield. Merancy said that her understanding is that it was phenomenal. Overall there were 1.200 sensors on the vehicle, quite a few of these were for the heat shield, across the center-line, around the tabs that hold the service module; everything was instrumented. NASA got a great deal of data that enhanced the ground sensing and wind tunnel sensing data which can only get so close, so there are many uncertainties. You initially have to oversize your heat shield a bit to cover the uncertainties and limitations of your ground testing.

Now with flight data, it gives the chance to fine tune the heat shield. They will be going to a block Avcoat instead of the present one big piece of Avcoat. Avcoat was used for the Apollo capsule heat shield and on select regions of the space shuttle orbiter in its earliest flights. It was put back into production for the study. It is made of silica fibers with an epoxy-novalic resin filled in a fiberglass-phenolic honeycomb and is manufactured directly onto the heat shield substructure and attached as a unit to the crew module during spacecraft assembly. PICA, which is manufactured in blocks and attached to the vehicle after fabrication, was used on Stardust, NASA's first robotic space mission dedicated solely to exploring a comet, and the first sample return mission since Apollo. See Figure 6.

Figure 6: The Orion heat shield was critical to the success of the spacecraft's first flight last December. After the flight it was sent to NASA’s Langley Research Center Thursday, June 4. The 16.5-foot-diameter heat shield will be integrated onto a high-fidelity Orion mockup later this year and undergo water-impact tests at Langley's Hydro Impact Basin next spring. (Image courtesy of NASA)

There were no fundamental surprises from the EFT-1 flight, but all of NASA’s data was fine-tuned with this test flight and especially with hyper-speed returns to Earth’s atmosphere, the less the uncertainty, the less the mass Orion needs to carry since a wider margin for error will not be needed. The heat shield alone is 5.5 meters worth of material; if we can shave even a little bit off, that’s a lot less mass.

Avcoat was used on Apollo, so there is no fundamental change in the material on Orion with regard to the heat shield. However, the thickness of the Avcoat needs to be determined. Right now to cover any uncertainties, most of the acreage of the heat shield is about an inch thick. If they could, for example, shave that down to ¾” and if they know there will not be so much heating in certain areas they can further customize how thick the coating needs to be. So better and better data will help them save weight and cost.

The 1,200 sensors on EFT-1

Those 1,200 sensors, are in addition to all of the regular sensors, and they will not all remain permanently on further flights. The normal sensors are on the thermal system to check temperatures on heaters and things like that. The heat shield alone had dozens of sensors. The additional 1,200 sensors were Developmental Flight Information (DFI) for extra data to verify flight tests and validate NASA models. Those sensors were accelerometers for structures, thermocouples for the heat shield and heating in other areas, acoustic microphones in the cabin to measure the interior noise and high frequency vibrations, forward bay and other area cameras—all to verify NASA’s model accuracy in every aspect of the spacecraft. There were pull sensors on the fairings to measure the dynamics as the fairings came off and so much more. See Figure 7

Figure 7: Like common rocket fairings, the panels support the spacecraft and help it endure the aerodynamic pressure, heat, wind and acoustics it encounters as it goes from sitting on the launch pad to traveling thousands of miles per hour in a matter of minutes. But unlike conventional fairings, Orion’s panels support about half of the weight of the spacecraft’s crew module and launch abort system, which improves performance, saves overall weight and maximizes Orion’s size and capability. (Image courtesy of NASA)

There will be more sensors as well on the next flight, EM-1, for the same types of verification.

Figure 8: Electronics architecture of Orion (Image courtesy of NASA)

The DFI system was all recorded on a separate computer aside from the standard on-board computer. Normal operational instrumentation will be fed into Orion’s standard on-board computer.

Shedding extra weight upon reaching the void of space

Several minutes into flight, when the panels no longer are needed, they are jettisoned using a series of pyrotechnic devices that must fire in precise sequence to move the panels away from the spacecraft and allow it to continue its mission.

See the video below.

This video shows the first test in a series of tests for the NASA Orion spacecraft's fairing separation system. Engineers made design changes to the system as a result of data collected during Orion's first test flight on Dec. 5, 2014. (Image courtesy of NASA and Lockheed Martin)



Budgets, schedules, risk

All spacecraft have a budget, a schedule and an amount of risk they are going to accept. Obviously, with people on board they have less risk that can be accepted; Curiosity Rover is a very expensive program and you want to make sure it gets to Mars, but you ultimately do not have a human life at stake there if it fails.

NASA has to accept less risk, but they have to do it on a budget and a schedule just like everyone else.

Contractors

Lockheed Martin is the prime contractor and they do all of the building, much of the analysis. NASA is the customer that works as a partnership with them. Lockheed delivers the system and NASA will operate it. There are hundreds of other contractors as well. Unlike Boeing and Space-X that have a different model as both builder and operator.

NASA does do some things themselves like the parachute system which is a government furnished system in which they design and test it. It then gets delivered to Lockheed. There is a sharing of where the best technical expertise lies, so things like interplanetary trajectory design in which NASA has a great deal of experience.

Analyses and models

For the power and thermal analysis, Lockheed has the models, where every piece of electrical equipment is located. NASA has profiles of how they turn that equipment on and off; NASA runs the simulations and see what their power margins are for any given point in the mission. Merancy and her team also run many “edge” cases, especially for thermal, so for example if one thermal loop fails then everything will be run on the other thermal loop. That would cause a mission abort and they would return home in this case. However, they would still need to ensure that they can do everything safely on the return trip home with a major failure like that.

Most of NASA’s design cases are around a failure and being able to make things still function in the mission. In a nominal mission they will have plenty of power and thermal capability, but once there is a failure, they still have to bring the crew home safely.

The Glass Cockpit and astronaut controls/switches

Even though Orion can fly fully automated, NASA has back-up capability so that the crew could manually pilot the spacecraft. They have rotational and translational hand controllers. On the three screens in the “glass cockpit”, there are buttons and a “swizzle” knob on all of them, so all of the screens for the crew will bring things up and the astronaut can press the right button or turn the “swizzle” knob. This allows far less than the 2,000 knobs and controls that the Space Shuttle had.

There is also one module, an auxiliary but control unit that has only a handful of switches for emergency situations. Things like switches for manual chute deploy, for example, but there are a very limited number of critical survival items that have an alternative means of deployment in the event the main control fails. There is also a Power bus panel with backup reset switches.

This makes for a much more “clean” and less cluttered cockpit.

Paper manuals vs. electronic procedures

So NASA essentially got rid of the bulky and heavy manuals that the Space Shuttle had and replaced it with electronic procedures on board, but the new system presents its own challenges. What if there is a last minute change? Now you will have to interact with the software and you can’t just ask for a faxed or e-mailed page.

Radiation challenges: The Van Allen Belt and Solar events

Orion will pass through the Van Allen Belt twice in the “Distant Retrograde” orbit, so there is some extra shielding, for example, for the Honeywell computers running simultaneously on Orion, but you are never fully protected. There are four of these fault-checking computers for redundancy so that if one gets a single-event upset, then astronauts can disregard that data and one of the other three will re-integrate into the system. NASA has calculated that the chance that all four computers will have an event simultaneously is very small, but they can also re-boot the spacecraft for example in a complete power failure due to these events. This is called the “dead bus” recovery capability. On Apollo 13 they lost everything, so now astronauts can recover from that as well and power back up.

Redundancy management

Autonomy is also being built into the power system so that if all of it shuts down, when it gets to a certain state of charge the system will begin to turn systems back on in the most optimum sequence so that the most critical systems go on first. Of course life support systems need to turn on as quickly as possible. Also, for example, do you turn on all four computers of do you turn on the thermal system? At what power level do they begin to turn things back on? So Merancy and her team decides what the most important systems will be and in what sequence they get powered up. The solar arrays will always be in a maximum position to acquire the best energy from the sun, but that may have to be re-adjusted as well.

Then there can also be unexpected Solar particle events as well. These are much more dangerous to the astronauts, so there are storage lockers on board in the backbone and when they get close to maximum dosages on their radiation badges, the astronauts will have to wedge themselves down into the storage lockers in the “heart” of Orion. Two fully-suited crew members will fit into each bay surrounded by a great deal of spacecraft structure for protection.

Some dynamic event situations like Main Engine Burn at the Moon, there is literally a window of only seconds to do the burns and if they are not done properly the spacecraft goes off skipping into space. So in that case there will be full redundancy powered up and everything on the vehicle will be powered up to ensure maximum capability. On the other hand, during quiescent days of coasting between the Moon and Earth, they can turn many non-essentials off.

This is a large part of Merancy’s role on the Orion program—that of Power and Thermal management; the operational management of what can or can’t be done at any given time during every phase of the mission.

Solar Arrays and battery power

Orion has four solar arrays and four main batteries. The main batteries are needed for example as the backup to the solar arrays in case they went out or there is a solar eclipse, such as being behind the Moon or the Earth. The batteries are also needed for when Orion returns to Earth because when the Service Module is jettisoned, the solar arrays go with that. So on re-entry Orion is on battery power from separation to splash-down and recovery. The batteries are sized to support recovery—four batteries of 30Ah each in the Crew Module. For re-entry, Orion is able to return on 3 batteries and NASA is now in the process of determining if it can come back only on two batteries.

If half the power was lost, NASA can actually turn of half the power drain since just about every major function is redundant. Mercancy believes that they should be able to since they can keep shutting down non-essential systems to save battery power in this case. There are a few things that need to be tweaked such as the heaters of which are balanced across all the channels and in this case they may have to move some of the heater power over to keep the spacecraft balanced.

A novel Carbon Dioxide removal on Orion

Merancy told us that a big improvement on Orion will be to use Amine Swing beds for Carbon Dioxide removal. This technique has enhanced reliability for space travel since it has no moving parts. This is a big technology advance for the Environmental Control and Life Support System (ECLSS) System. This system is being tested out on the International Space Station (ISS) and it has gone phenomenally well. See Figures 9 and 10.

Figure 9: Amine filter beads (NASA TV)

Figure 10: NASA astronaut Kevin Ford, Expedition 34 commander, performs maintenance on the Amine Swingbed assembly in the Destiny laboratory of the International Space Station. (NASA TV)

Sensor Test for Orion Relative Navigation Risk Mitigation – DTO 703 (STORRM)

Merancy was also a part of the STORMM DTO which is a test for the future navigation sensor that is a flash LIDAR on the second-to-last Shuttle flight. The flash LIDAR was flown in the payload bay of the Shuttle next to their other ranging sensor. The crew did a demonstration rendezvous with Merancy’s system which was the first use of the flash LIDAR system in orbit. This system will provide range and range rate and relative attitude for when trying to rendezvous with very tight tolerances on the docking adapters.

Summary

The caliber of the talented people at NASA are exemplified in people like Nujoud Merancy and others I have met during my various NASA visits. These technical experts in their field are the ones who make things happen, on time, in budget and with an emphasis on safety for the astronaut travelers who will journey beyond the Moon to Mars and other deep space endeavors in the future. What was once science fiction is becoming a reality with such technical expertise and experience that the NASA teams have to make such events happen in our lifetime.

Stay tuned for many more technical articles to come regarding NASA efforts.

References

1 Orion, Space Launch System, and Ground Systems Development Operations, Dan Dumbacher, Deputy Associate Administrator, NASA Exploration Systems Division, 2014

2 Independent Verification and Validation of the Orion Multi-Purpose Crew Vehicle Active Thermal Control System Performance, Xiao-Yen J. Wang, NASA Glenn Research Center, Cleveland, Ohio

3 The Prospect of Responsive Spacecraft using Aeroassisted, Trans-Atmospheric Maneuvers, Dissertation, Robert A. Bettinger, Captain, USAF, Air Force Institute of Technology.

4 A Comparison of Two Skip Entry Guidance Algorithms, Jeremy R. Rea, NASA Johnson Space Center; Zachary R Putnam, The Charles Stark Draper Laboratory, Inc., Houston, TX.