Today XCOR begins a full week at the American Geophysical Union’s 46th annual Fall Meeting in San Francisco. We’re talking with Khaki Rodway, Director of Payload Sales and Operations, about the future of research opportunities onboard Lynx as they relate to AGU participants.
Khaki handles all research and education missions onboard Lynx flights. She is the “Your Mission. Our Ship.” side of the XCOR equation.
The XCOR team, including Khaki, will be at booth 245 from Monday, December 9th through Friday, December 13th. Please drop by and say hello!
Khaki Rodway: XCOR is at AGU to deliver a glimpse of the emerging opportunities onboard Lynx for anyone involved with atmospheric science, planetary observation or space physics (for instance). These opportunities are new and provided through Lynx, our commercial suborbital vehicle.
So what I am doing this week is talking to scientists about the paradigm shift Lynx provides the AGU community.
BC: For the uninitiated, can you elaborate on that shift, and how Lynx connects with AGU participants?
KR: When it comes to space-based research and observation, scientists now have the ability to get into the field as never before, and get to where they want to go with Lynx.
BC: And what are the main advantages of Lynx for atmospheric scientists, planetary scientists and space physicists?
KR: It’s threefold: First it’sthe ability to fly at low cost, which makes high flight rates achievable. Second, the fact that researchers can fly with their experiments will be a game changer. And third, the greatest advantage, the one that makes Lynx so exciting and beneficial to scientists, is that each flight can be entirely dedicated to the scientist’s mission–they don’t have to share their g-profile or pointing profile with other experimenters.
Scientists will be able to gather in-situ measurements at multiple points in the atmosphere or direct a telescope at a specific planetary object, for instance.
BC: Can you give some specific examples of how advances in suborbital space flights will change research and experimentation for the better?
KR: Sure. Take space hardware, where automation is the norm.
Before hardware is ever on orbit you have to know that it’s going to work. Because if it doesn’t work you can’t just go up there and fix it.
But if you can do your calibration tests with a human in the loop and fly frequently at low cost in a relevant environment, you can save yourself time and heartache by knowing that the instrument will work the first time it’s put on a satellite.
If something goes wrong with your hardware, your experiment, you’d like to get your hands on that hardware and fix it… but you can’t. After launch, there is no way to tweak and modify anything. Perhaps months later you’ll retrieve it.
Lynx is designed for low cost, high frequency flights. By comparison–take sounding rockets as an example. Much of the research conducted at this level of the atmosphere currently involves sounding rockets, and those are about ten times the price of a Lynx flight, maybe a few flights per year per experiment.
And this ability for Lynx to fly at such low cost and high frequency makes high flight rates achievable, which is what makes the whole future of suborbital research so attractive. With increased frequency, you have the opportunity to test equipment in-situ and know much more about what to expect well before launch.
With Lynx, we can dial up flights on a couple of hours’ notice, which matters a lot for anyone wanting to perform research at a pace that’s interesting.
BC: OK so that’s low cost and high frequency flights, and in-situ measurements for instrumentation development. How would Lynx be relevant to, for instance, an atmospheric scientist?
KR: Let’s say I’m a researcher who wants to gather data on noctilucent or polar mesospheric clouds. These clouds form spontaneously and hang around for several hours. With Lynx rapid call-up time—Lynx can be ready to fly in 2 hours—it can get me to 80 kilometers before the clouds disappear. That has not been possible until now.If the weather changes and I only have two hours to fly to 80 kilometers, I now know I can do that.
BC: So a researcher can have increased frequency with Lynx, and at a sharp decrease in cost from today’s offerings. What else?
KR: One of the most interesting opportunities on the horizon with Lynx is that Lynx can be used as a dedicated space-based research vehicle that flies a single scientific mission. Much like oceanographers and marine geoscientists have their ocean-going research vessels that go to their areas of investigator interest, Lynx can do the same for space researchers. Space scientists can get into the field, collect samples at a particular altitude in a particular part of the world, or look at specific object in the solar system or area of the Earth when and how they want.
It is my flight, “my” vehicle with a scientific mission.
BC: Last question: What is the “Ignorosphere”.
KR: The Ignorosphere is a phrase scientists use for the Mesosphere/Lower Thermosphere (MLT) region, which is at about 50 to 140 km altitude, and is likely the least sampled and understood region of the Earth’s atmosphere.
It’s the region of the atmosphere where all of this research will happen.
Scientists call it the Ignorosphere because it is above the region accessible for sampling by aircraft and balloons, and below the region of satellite access. Sounding rockets do get into the MLT, but they quickly pass through it.
Lynx is going directly into the MLT, which means scientists can examine up close transition zones such as the mesopause and turbopause, or Earth’s highest clouds known as Polar Mesospheric Clouds (PMC’s), or the regions where solar UV variability has its greatest impact gravity waves dissipate momentum. With Lynx floating in this region for several minutes, scientists now have the ability to do fine scale in-situ sampling of key chemical trace gases, meteoritic dust, isotopes of trace gas elements, water vapor, sulfates, CO2, just as an example. All this can be accomplished frequently, repeatedly, and at an extremely lower cost than existing platforms or capabilities.
The Lynx flight panel is designed around a two-screen electronic flight instrumentation system. This system gives our pilots all the flight path and performance they require on the left screen and, on the right, all the information necessary to manage the engine and Lynx systems. Other instruments surrounding the main screens are present as backups. It is hinged around a center post and swings out for easy maintenance.
More on cockpit origins and progress in the coming weeks.
Pictured is an illustration of the final product in action at about 100 kilometers.
The propulsion system on Lynx is supported by a steel truss that attaches to the rear firewall of the fuselage. Composite blast shields surround each engine.
In front of the engines, the truss supports all the valves, pumps, and plumbing needed to control and deliver fuel and oxidizer to the engines. In these shots, engineer Jeremy Voigt checks for small control line leaks using a stethoscope.
As we discussed recently, XCOR engines are set apart from the rest by their long life, reliability and reusability.
But they are also set apart by how they are pump-fed.
XCOR’s rocket piston pump simplifies the overall propulsion design versus traditional rocket engines. It lowers the overall weight of the vehicle by enabling the use of low pressure liquid oxygen and conformal kerosene tanks, and enables the quick turnaround of the vehicle since it enables “gas and go” rocket engine operations.
Usually high-performance rocket engines use turbo pumps that include complicated design features, extreme internal operating conditions (thus needing exotic materials), have limited (bounded) range of thrust once they are designed, and typically require extremely-skilled, highly-paid staff to produce and maintain the pump inventory. The typical life-span of a high performance rocket turbo pump today is about 30 minutes (sometimes less, sometimes more) before it renders itself unusable and in need of replacement. A good rocket turbo pump for an upper stage expendable launch vehicle will cost between $500,000 and several million dollars apiece.
By comparison, XCOR’s piston pumps require no exotic manufacturing processes or materials, and the component parts can be built by readily available high-precision machine shops. The pump may be serviced on a typical shop bench in under a few hours by a technical school graduate or junior grade FAA licensed Airframe & Power Plant (A&P) mechanic. The XCOR rocket piston pumps can then be mounted on a rolling test trailer, checked-out the same day and installed on the Lynx. The all-in purchase and assembly price is an order of magnitude less than a turbo pump of similar capability.
Our rocket piston pumps will undergo regular preventive maintenance as we check on internal wear and tear, replace seals, and ensure the pumps are ready for flight. XCOR believes that rocket piston pumps in use for Lynx will last hundreds if not thousands of hours, with regular preventive maintenance. And at three minutes per flight, this adds up to a lot of rocket flights!
Each piston pump can run at a different speed to supply different amounts of propellant for various engine outputs within a fairly broad range of thrust levels. They can also provide propellants for more than one engine at the same time.
For example, recently XCOR sought to increase the thrust of an engine by 30 percent. In the turbo pump world, that probably would have precipitated a completely new design of the turbo pump, including millions of dollars of non-recurring engineering and one to two calendar years of time. In our case, we had significant margin and just turned the pump speed up to achieve the desired thrust level.
In the Lynx, each pump is so powerful it can drive propellant for two (of the four) main engines with significant margin. In other words, one pump is so powerful it provides the liquid oxygen for two engines! And a second pump provides the fuel (kerosene) for the same two engines. This makes the baseline for the Lynx propulsion system four pumps and four engines. Each engine is roughly 3000 lbf of thrust.
Given all the advantages of the rocket piston pump above, one might ask why turbo pumps are ever used in rocket propulsion systems. For smaller thrust levels below 60,000 to 100,000 lbf of thrust (depending on the fuel, liquid hydrogen or kerosene, respectfully), we ask the same question. But above these thrust levels, the turbo pump output performance per unit of weight becomes an advantage over the piston pump.
In later posts we’ll discuss more about the propulsion system, piston pumps, and at a high level, the thermodynamic cycle that makes it all work.
Tomorrow we will show you a test article for the cockpit.
Engineer Mark Street assembles a sub-sonic wind tunnel model Lynx, which was used at the U.S. Air Force test facility at Wright-Patterson Air Force Base near Dayton, Ohio.
In addition to computer modeling with computational fluid dynamics, wind tunnel models provide the necessary real-world data that together informs the final shape of the vehicle. We will cover all of these topics and more in the near future.
Tomorrow we cover some questions from the week, and update you a bit later on where you can find us on the road.
Lynx landing gear is carefully designed to be as light as possible while handling all possible load cases. Many tests are conducted to ensure the gear will withstand the forces involved. Here XCOR Engineer Brandon Litt prepares a Lynx landing gear prototype for a drop test. Over the coming weeks and months, we will show you more of the process around landing gear development.
Tomorrow we’ll show you a shot of the Lynx subsonic wind tunnel model. It’s pretty awesome, look for it at 9am PST.
Before creating the final cockpit, we first made a full-sized engineering model to help us engineer its various sub-systems including avionics, life support, ingress-egress, seat hardware, payload locations and more. This model was pulled from a mold that was also used to make the final item.
In this photo, the engineering model of the Lynx cockpit has just been pulled from its mold, which sits upright and partially obscured by the tarp on the left.
XCOR’s Derek Nye and Ray Fitting prepare the Lynx truss for a test day.
XCOR follows a rapid design-build-test approach to developing new products and systems critical to the success of all XCOR programs. We excel at the fast hardware design, build and test of non-toxic liquid propulsion systems. This includes our Lynx main engines, as discussed last week. While non-toxic systems are critical to the overall safety of the Lynx system, they are also vital to the low cost of operation and ownership of Lynx.
“Build a little, test a little”
This “build a little, test a little” approach allows for many Lynx concepts to be evaluated, physically validated and changed rapidly using inexpensive and practical analysis and test methods, rather than relying solely on costly and time-consuming modeling and simulation. It also allows for other projects to generate serious results.
For example, other programs have received multimillion dollar contracts to study pumps without building any hardware. Eventually, a pump may be produced for many more millions of dollars. On the other hand, over a period of 2 years and at dramatically less cost, XCOR has worked with ULA to produce a working liquid hydrogen pump that demonstrates convincingly that it will work for a similar-sized engine with much higher reliability and reusability, and again, at far lower cost. Such outcomes are possible due to frequent and routine testing followed by fast iterations. This produces truly innovative results, and a serious increase in safety and reliability.
When fast iteration is pursued, XCOR focuses on critical operational parameters and requirements for propulsion such as low production costs, ease of maintenance, long life, full reusability and long term producibility. For long-term producibility, we are designing to anticipate the related techniques, materials and processes that may be readily available 20 to 30 years from today.
There are further critical elements, and by focusing on these parameters we drive down total cost of ownership of our systems through upfront procurement cost, maintenance man hours per flight, vehicle turnaround time, life of the product, cost of replacement parts, and reduced support crew and equipment. This positive feedback loop is a benefit to our customers, but also enables enhanced safety. The lower cost of the system to operate, the more that system may be flown. The more it is flown, the more we learn. And the more we learn, the safer we can be.
Design-build-test and XCOR culture
Mobile test stands also feed into our approach. With only minimal fixed test infrastructure at remote locations, we eliminate the need for separate crews reporting to different parts of a larger organization. This fosters a unified design-build-test culture in our company. All equipment and personnel return to the hangar at the end of each test day. Propulsion systems under test are worked on in the comfort of the hangar with all tools and personnel available, then taken to the nearby test site. All engineers and technicians work together toward the common goal of a working product.
Nothing is duplicated, we are one team, costs are contained and safety improves yet again.
Tomorrow: The importance of an actual Lynx cockpit engineering model
In this image, XCOR engineer Brandon Litt makes final preparations to a Lynx supersonic wind tunnel model before performing a test at the storied NASA Marshall tri-sonic wind tunnel in Huntsville, Alabama.
Above, a NASA Marshall spaceflight engineer tests a similarly sized supersonic wind tunnel model of the Space Shuttle in the same facility during the early years of the Shuttle program. The results of the Shuttle tunnel tests were critical to the go-forward decision to build and fly the Space Shuttle.
We believe that test pilots and customers alike require confidence that the spacecraft they fly on has been evaluated and tested extensively prior to flight. And in this day and age, many rely on computer simulation to be sure that their aircraft can perform at the level required.
XCOR used Computational Fluid Dynamics (CFD) and other software analysis tools to design the shape of the Lynx aeroshell. However, things really accelerated when we were able to perform a series of seven subsonic and supersonic wind tunnel test campaigns at United States Air Force (USAF) and NASA labs.
Typically, the faster the tunnel, the smaller the available space. Supersonic wind tunnel models are traditionally smaller than their subsonic counterparts due to the available space in supersonic tunnel test sections. The models must not only fit, but have room to change pitch and yaw inside the tunnel without approaching the side walls of the tunnel. If the model is too close to the walls, edge effects from the walls can be picked up in the data, and ruin the test.
Because supersonic wind tunnels are so small, Lynx models themselves must be highly precise to adequately simulate the full scale spacecraft. The models have many pieces that are interchangeable to test different configurations of the vehicle. For example, a model may have 5-10 different nose shapes, 5-10 different permutations of wing aileron settings, and so on. Because of this, the models can become quite expensive, sometimes approaching several hundred thousand dollars.
Because the actual Lynx is so much smaller in real life than the Space Shuttle attached to the solid rocket boosters and center fuel tank, the Lynx model shown above is actually much larger (almost 3-4 times larger) in scale than the Space Shuttle model.
Tomorrow we answer some of the week’s questions and let you know where you can find XCOR on the road in the near future. In particular, we’ll have some updates for future appearances of XCOR team members and the Lynx full scale model.
The Lynx flight weight fuselage is mounted on the fire wall test stand, awaiting re-installation of the engine truss structure.
On Wednesdays we highlight progress on various structural components such as the fuselage, strakes, wings, nose and landing gear.
Always build a house with a strong foundation. Always anchor a suspension bridge into bedrock. A similar principle holds true for spacecraft: they must always be built on a solid structural core that can stand up to flight in harsh environments.
The Lynx structure consists of several critical components: the fuselage (containing the liquid oxygen tank), the wings and control surfaces, wing strakes (containing our kerosene fuel, and main landing gear), cockpit, and nose (containing the nose landing gear).
Our spacecraft is a complex assembly of highly-engineered structures designed to maximize strength and minimize weight. Each have their own functional requirements, and must serve the function of the vehicle as a whole. More so than any other application, form follows function very tightly on a high performance launch vehicle.
At the center of the Lynx is the fuselage. The fuselage holds the liquid oxygen tank, and all other major structural components attach to the fusleage. These include the truss structure that holds the propulsion system (Monday’s post), the cockpit (yesterday’s post), the wing strakes that hold the kerosene and the main landing gear, the nose structure, and the wings with their control surfaces.
The fuselage can be seen in the photo above. In it, the carbon fiber structure has been painted to protect it from the sun’s UV radiation, as UV can degrade the carbon fiber structure. The fuselage is sitting on its cradle on the Lynx firewall test stand, waiting for the propulsion system to be re-attached.