XCOR Lynx: Thrusters!


Engineer Jeremy Voigt tests the Lynx 3N22 Thruster prototype. This thruster has been fired hundreds of times, and its spark torch igniter tested thousands of times.

The Lynx reaction control thruster (the 3N22) is a non-toxic, high performance, bi-propellant thruster. Bi-propellant means that the thruster uses a fuel and an oxidizer to run. The 3N22 has many attributes that make it perfectly suited to Lynx operations, for future use on satellites, and human spaceflight vehicles in orbit.


Astronaut Buzz Aldrin visits the XCOR hangar and fires the 3N22 thruster

The 3N22 has been fired hundreds of times. Its spark torch igniter, along with all of its predecessors has been tested tens of thousands of times.

Because XCOR uses nontoxic propellants, the thruster can be readily tested inside the XCOR hangar and handled without the need for more traditional and costly pressurized hazmat suits (commonly called SCAPE suits, for “Self Contained Atmospheric Protective Ensemble”).

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SCAPE technicians ready for action

Overall savings in recurring and non-recurring costs for XCOR in using the non-toxic 3N22 is estimated to be over several million dollars, and a similar amount on an annual basis. Savings are derived from avoiding the following: costs associated with SCAPE suits, handling of toxic chemicals like hydrazine or nitrogen tetroxide, and the difference in cost savings between the fuel XCOR uses and hydrazine. These savings are passed on to our clients in the form of lower prices and safer flights.

As with the main propulsion systems discussed last week, the reaction control thrusters use liquid propellants. The 3N22 uses a combination of gaseous oxygen and our own proprietary fuel blend and can be considered “gas and go.” The thrusters require no touch labor between flights except for refueling from propellant storage tanks.

There are a total of twelve (12) 3N22 thrusters on the Lynx vehicle. They are mounted in six different locations, and are implemented with dual redundancy. Each thruster in a cluster of two runs off of separate feed systems to ensure operability even if we experience an anomalous condition with a thruster or feed system. The thrusters are located on the top side of the Lynx on the nose and the engine cowling (for nose up/down pitch control), on the two sides of the nose of the Lynx (for left/right yaw control) and on the two wing strakes (for roll control). You can see their position in the Lynx image (pairs of small black dots) and diagram (wherever RCS is mentioned) shown below.

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Tomorrow we’ll hang out in the XCOR rocket engine test bunker.

Where in the world is XCOR?

Lynx at ISPCS 2012. Photo by Bill Faulkner.

In October XCOR will be back on the road at the following locations. This list will probably change, and we will update here and on Twitter if it does.

ERAU Career Services Industry Expo in Prescott, Arizona

Connect with XCOR staff and executives to explore and discuss career opportunities at the Embry Riddle Career Services Industry Career Expo October 2-4 in Prescott, Arizona .

Directions to campus
Expo details
Information for Job Seekers

ISPCS 2013

XCOR Chief Operating Officer Andrew Nelson will speak on “The Marketplace” panel October 16 at the International Symposium for Personal and Commercial Spaceflight in Las Cruces, New Mexico.

More about ISPCS here.

XCOR Lynx: DIY Aerodynamics


Engineer Mike Valant drives an XCOR wind test truck back and forth on the taxiways of the Mojave Air and Space Port during a test series.

In 2009 XCOR built a highly precise sub-sonic wind tunnel test model of the Lynx. For some preliminary data before actual wind tunnel visits, we ran tests using our ‘DIY truck tunnel’ as shown above. The truck and its fixtures include precisely instrumented appendages, structures and bit of computing and data recording capability. We also used the truck tunnel after the sub-sonic wind tunnel tests to experiment with some additional design features before returning to the real tunnel a second time.

By the way, this is not the first time that this particular technique has been applied in Mojave and “other places” in the Antelope Valley for aerodynamic development. We wish we could say we invented this technique but we did not. It has been used for many years by both neighbors in Mojave and neighbors to the west and south of us.

Stay tuned tomorrow as we answer your questions and update you on where you can find us on the road!

XCOR Lynx: Mockups for structures

Engineering mockups are very important tools for finding interferences and rapidly moving through concepts. Before detailed 3D models—and then drawings—are made, rough mockups are created using very inexpensive materials and easy assembly techniques. In this photo, XCOR CEO Jeff Greason examines tank placement in an early mockup of the Lynx engine truss made with plastic, PVC tubing, cardboard tubes, duct tape (what would we do without duct tape?!), composites and pour-in-place foam.

Tomorrow: DIY wind tunnel tests.

XCOR Lynx: Strake test article

Building a prototype spacecraft requires a lot of research and development test articles before the final item is fabricated. In the composites shop, a structural test article for the strake is fabricated by Erik Anderson and intern Nick Cantwell.

Top right: Notice the fiberglass cockpit fit check model at an early stage of development.

Stay tuned for mockups in the morning.

XCOR Piston Pumps – the Holy Grail

An XCOR rocket piston pump with colors so intense, it appears ready for the Fourth of July

Welcome back!

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.

Where in the world is XCOR?

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Above, the full-scale Lynx model at the Next Generation Suborbital Researchers Conference in Broomfield, Colorado this past June.

We have had a lot of questions the past few weeks about where to find our full-scale model this fall.

Over the coming month, our Lynx full-scale will be back on tour in Texas!

For starters, you can catch Lynx at the Commemorative Airforce Airsho in Midland, Texas on October 12-13. There will be a very good contingent of XCORians that weekend to answer any questions, and we’d love to see you there.

As always you will be able to hop in and experience Lynx for yourself.

And as more travel dates appear, we will let you know!

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An update on that question about who made the NASA Marshall tri-sonic wind tunnel. The 14-Inch Tunnel began its life with the Army in the late 1950′s under the Army Ballistic Missile Agency (ABMA). A bit more on the Shuttle history with the tunnel here.

XCOR Lynx: Aerodynamics — Sub-sonic wind tunnel model assembly


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.

XCOR Lynx: Landing Gear 101 – Drop Tests

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.

XCOR Lynx: Cockpit engineering model

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.

It’s all about the gear on Wednesday. Stay tuned.