Project Earendel: Open Source Rockets
Project Earendel: Open Source Rockets
Open source space access. Build, fly, and release drawings for a liquid powered suborbital rocket.
Open source space access. Build, fly, and release drawings for a liquid powered suborbital rocket. Read more
About this project
Earendel will be the first vehicle capable of reaching space, i.e. greater than 100 km, with an entirely open source design. Every component, design code, flight code, and vendor part number will be fully documented and available in a manner that will allow anyone to make, study, or modify the vehicle. Earendel is the old English name for the morning star. Similarly, we hope to act as a guide, making space accessible to everyone.
Why is this necessary?
In 1957, the first satellite, Sputnik, was placed in orbit. In 1961, the first man, Yuri Gagarin, orbited Earth. In 2015, over half a century later, there is no way for anyone short of a major government or multi-millionaire to access and use space. This is equivalent to no consumer cars in 1942, no private airplanes in 1959, or no personal computers in 1994.
The two major reasons for this situation are that building rockets is expensive and, since a primary use of rockets has been as a weapon, much of the development was classified. While the commercial space access market is growing, namely with SpaceX, Blue Origin, Sierra Nevada, and others, they have not made a dent in the most significant issue: an almost complete lack of open source data on how to build a Space Launch Vehicle. To date, the best open information is NASA SP-125 and the 8000 series monograms, both of which are from the early 1970s. As recently as 2013, even some of these basic texts have been temporarily taken off NASA’s public database. In order to ensure that we, and future generations, can have access to space, we need to act to create open source documentation on how to build vehicles capable of reaching space - and the best way to find out how to do something is to go out and do it!
This project’s immediate goal is to put a payload into suborbital space, but to do it with a completely transparent design (i.e. all part drawings, code, and design guidelines will be released via normal Open Source standards). Furthermore, a detailed design handbook will be published to allow anyone to understand these designs and build upon this work. At the end of the Kickstarter, the maker community will have a better baseline for designing high altitude rockets.
The goal for the vehicle is to get a payload equivalent to a standard cubesat (1.33kg) into space (above 100 km). To do this, we will build the rocket design shown below, but we need your help to bring the dream of personal spaceflight closer to everyone.
The Earendel rocket is a single stage liquid sounding rocket. It is powered by a 200 lb thrust Liquid Oxygen (LOX) / Isopropanol (Rubbing Alcohol) film-cooled stainless steel rocket engine. For simple, robust operation, the vehicle is a pressure fed system running at 180 psi chamber pressure. The LOX is self-pressurized and the fuel is pressurized by stored gaseous nitrogen. For ease of construction and repeatable assembly, the propellant tanks are machined aluminum and form the primary structural load paths. All the valves are solenoid actuated or motor driven to simplify plumbing by removing pneumatics. The control computer is a commercial Gyroscope, Accelerometer and GPS running on Arduino hardware for easy accessibility. The nosecone and recovery system are standard high power rocketry parts modified to allow for high Mach operations allowing us to leverage existing components. The vehicle is 6ʺ in diameter, 8.5’ tall, and weighs 76 lb at takeoff. Numerous cameras are employed to document the flight both on the vehicle and on the ground.
Simple rockets, buildable and flyable in the same realm of complexity as building kit cars or your own boat.
This means no toxic propellants, no helium, and large safety factors (2x or greater) on pressurized components. All parts will be released as open source and will be made as simply and cheaply as possible for the end user. We will use a kit style design with a few complex machined parts capable of being sent to a machine shop or 3D printing vendors and with the majority of components assembled by hand tools. This philosophy trades some performance for robustness and low cost, but is more than sufficient for a suborbital vehicle.
What do you get out of this?
Awesome swag! And more! You get access to a detailed rocket design capable of accessing space while ensuring open availability of the material for the future builders. There are, of course, some cool posters, pendants, and patches as well as the opportunity to put components into space for a reasonably small outlay.
How do you know I can build the vehicle?
The general vehicle was laid out above, but something as complex as a suborbital rocket needs slightly more planning that a paragraph. Below are some details of the budget, timeline, a detailed part listing, and the basic design of major components.
Part Design Detail
- Engine: The main propulsion is a pressure-fed film-cooled engine. It runs at 180 psi for relatively low pressure tanks and produces 200 lb thrust. The design, shown in cross section, is a machined concentric tube chamber. The injector is a metal 3D printed piece with integral inlet and pressure ports. It uses a sparse field of unlike doublet impinging jets and film cooling - effectively boiling alcohol on the chamber wall to keep it cool. The engine is designed for ease of use, simple fabrication, and durability and is expected to achieve a sea level Isp (specific impulse) of 205 sec with a 90% efficiency.
- Tanks: Tankage is one of the most difficult components of a rocket to fabricate due to their relatively large size and thin walls (as well as high pressure, vehicle stress, etc.). To simplify production, the tanks will be machined assemblies with bolted connections and fluoropolymer seals. The endcaps are machined from billets and the body from thickwall tube. At this scale, machining is the quickest and cheapest production method (almost no tooling costs). The tanks run at 220 psi and have a factor of safety of 2.5. This high safety factor also minimizes stress on the seals for more robust sealing.
- Fincan and Fintabs: The vehicle needs control to achieve its mission and this will be provided by fins and actuated fintabs. Normally, the vehicle has fins for aerodynamic stability so that it will point in the apparent wind direction and not tumble out of control. To stabilize the rocket, fins are integrated with the rocket to move the center of pressure behind the center of gravity, just like a dart or shuttle cock. To make sure Earendel remains on its design trajectory, a set of servo-actuated fintabs will be added to actively control the vehicle via the guidance computer.
- Computer: The rocket requires limited computing power but lots of analog and digital inputs and outputs. There are nominally 33 channels (13 Analog In, 5 Digital In, 15 Digital Out), as well as a few serial communication ports for GPS, antenna, IMU, and data logging. The system only needs to operate at a relatively slow 100 Hz rate so the total processing power is fairly low, allowing for the baseline to be a single Ardiuno Mega computer. In addition to the flight computer, there are two ground computers required for operating the test stands; these are also baselined to run on Arduinos. The igniter test stand has been demonstrated with 5 Analog In channels, 1 Digital In channel, and 4 Digital Out channels with a serial communication on an Arduino Leonardo. The wiring diagram and necessary code is posted on the Project Earendel website.
- Igniter: If the injector is the heart of a rocket, the computer is the brain, and the pressurant system the lungs, then the igniter is the spleen- not sexy, often overlooked, but without one you would probably die. The igniter is a completely separate small engine with about 1 lb thrust and runs on gasified LOX and a small tap off of the fuel tank. It is spark ignited by a COTS (Commercial Off The Shelf) exciter printed out of bronze infused steel and runs fuel rich enough to not burn up. It is possible to directly ignite engines of this size, but it is somewhat tricky due to the high probability of hard starts (i.e. blowing up the engine).
- Main Valve: The main run valves are piloted solenoid valves with COTS solenoids and a custom body. They are 3/8” poppet valves and have brass bodies and reinforced PTFE seats. As shown in the image, the valve uses 3D printed mounts and a main body for ease of production. The other custom valve is the LOX main vent valve which is a servo-driven poppet valve. The vent valve is normally open, that is to say safe, in case of a loss of power.
- Pressurization System: The press and purge systems have as many off the shelf components as possible. The valves are COTS solenoid valves, paintball regulators (with some modified springs for set pressures), and associated other paintball components. The tanks are custom parts made using Al 2024 tubing and composite endcaps.
- Recovery: Recovery is historically one of the hardest parts of a rocket flight, amateur and professional alike. Indeed, many rockets do not even attempt recovery to save time, money, and mass. Since Earendel will carry payloads, there will be a recovery system based on traditional high power rockets. This is a 3 stage system. The first stage jettisons the nose after engine burnout. The second stage is a drogue parachute deployed during reentry to keep the vehicle at a low speed and the payload out of the airstream. The third stage is a main parachute that will deploy at ~1000 ft above ground level to lower the vehicle gently to the ground.
In addition to detailed vehicle and component design, we have done an in-depth budget and project planning to ensure we can make the flights happen on time and within budget. An overview of the budget and timeline is shown below with more detailed information available on the Project Earendel website.
Who is the Team?
Currently the team is led by Lloyd Droppers and Jasmine Cashbaugh. Lloyd is an aerospace engineer with a decade of experience in building rocket engines and various other mechanical components, mostly at New Space companies, including launching multiple liquid and solid powered rockets. Jasmine is a mechanical engineering PhD focusing in robotics with 3 years of experience at Lockheed Martin Skunkworks. Provided we get the backing to build the vehicle, we have sufficient technical expertise, but additional team members will be added as necessary to finish the vehicle and documentation in a timely manner. In addition, credit to Brooks Cashbaugh for the poster artwork; Mateo Zlatar and Open Source Hardware Association for part of the logo artwork; and Purdue University Hybrid Rocket Project for the hybrid motor test video.
Risks and challenges
As with all projects, there is an element of risk - maybe more risk than usual considering the high temperature, high pressure, and high speeds involved in the project. In addition, there are the more normal programmatic risks of time, budget, and legality.
What if you can’t complete the project?
All things are possible given time and money. That being said, if we run out of time, it will just be delayed; if we run out of money, that is a different issue. No matter the final end state of the project, we will, at an absolute minimum, publish all of the work done with the next steps outlined for anyone interested in following the project. However, we have experience with designing, building, and flying solid, hybrid, and liquid rockets as well as small aircraft which gives us confidence in our ability to deliver on the project.
Is this legal?
Yes. There are provisions in the FAA Procedure for Handling Aerospace Matters (JO 7440.J) allowing for “Amateur Rockets.” Suborbital flights up to 150 km with total impulse less than 200,000 lb-sec are covered in this category.
Testing rocket engines and components is a matter of meeting local fire code, noise ordinance, and OSHA regulations. As long as the propellants are not explosives, it is mostly quantity, distance, and choosing appropriate sites to test in - mostly fireproof and away from other people. The plan is to test at the FAR site which is a publicly accessible rocket test site in Mojave, CA.
Oddly, one of the biggest questions is ITAR (International Trafficking in Arms Regulation). This is legislation that is intended to stop the export of weapons outside of the United States, but is much more pervasive and covers all rockets and any technical information about them. However, there are provisions, specifically 120.11(a)(2) “…subscriptions which are available without restriction…” amongst others, allowing for dissemination of public domain information, and, as the project is completely open source, it is definitely public. If you’re interested, the relevant law is at https://www.pmddtc.state.gov/regulations_laws/itar.html. If you’re a US citizen, also please consider contacting your elected representative requesting reducing ITAR and other anti-freedom of speech legislation.
What’s the worst that could happen?
As my old lab manager used to say, “It could blow up.” This, and other safety concerns, are taken very seriously and all rocket tests and high pressure testing will be done remotely and in a safe manner. This is also why government safety agencies such as OSHA, fire departments, and the FAA are necessary and useful to ensure compliance and, thus, the safety of all participants and uninvolved parties. We will comply with the appropriate regulations as well as use hard-won experience and common sense to keep the program safe and moving forward.
In addition, flying rockets is inherently risky and, in the case of a crash, the best effort will be put into returning payloads, but no absolute guarantee can be given on their safe return.
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