Stoke Space: All you need to know
Stoke Space is building a fully and rapidly reusable orbital class rocket in a way that nobody has ever seen before, so in this article you will learn all you need to know about Stoke Space and their Nova rocket, and the absolutely genius systems powering it.
Stoke Space & Nova
Stoke Space was founded in 2020 by 2 former Blue Origin employees: Andy Lapsa and Tom Feldman, with the goal of building a 100% reusable rocket. Reusable rockets lower the cost of spaceflight, enabling more frequent launches and making space more accessible for everyone.
The rocket that they are building is called Nova and it is expected to make its debut in 2026. Standing at 124 feet or 38 meters high, it consists of 2 stages and will be able to carry up to 5 tonnes into Low Earth Orbit. Its first stage will use Liquid Oxygen and Liquified Natural Gas as its propellants, and its second stage will run on Liquid Oxygen and Liquid Hydrogen.
Render of Nova (Stoke Space)
The reusability of the first stage is quite similar to that of for example SpaceX and their Falcon 9, where, after stage separation, the booster returns to the launch site and lands. The 2nd stage however, is very unique.
2nd stage
In 2022, their 2nd stage prototypes already had over 20 static fires under their belt, and in September 2023 they performed a 10 meter hop test.
Hopper 2 doing its 10 meter flight (Stoke Space)
The second stage is driven by a single turbopump assembly that powers 30 separate thrust chambers, which surround a heat shield that is used for reentry. The engine uses an expander cycle, where cryogenic propellant, in this case liquid hydrogen, flows around the thrust chambers and cools them down. For Nova not only it flow past the chambers, but during reentry the hydrogen also runs past the heat shield, to also keep it cool. As this hydrogen absorbs heat, it warms up, and turns into a gas. Most of this hot hydrogen gas is sent into the combustion chambers to generate thrust, but a very small amount of this hydrogen gets sent to power the turbine that drives the engine’s turbopumps. This is a genius way of keeping the heat shield and engines cool, while powering the engines at the same time.
Schematic of Stoke Space’s 2nd stage engine (ZenothKSP)
Originally SpaceX wanted to use active cooling for Starship's heat shield, where liquid methane would be released through tiny pores in the heat shield’s hottest areas during reentry. They eventually decided not to implement this system due to concerns over mass and extra plumbing, which could negatively impact performance. Instead they now use ceramic tiles, which work nearly just as well, while weighing less. Now the reason Stoke Space is still using this actively cooled heat shield is because it is a lot more integrated into the vehicle, because like explained previously, the cooling system of the heat shield also powers the engines. Nova’s smaller heat shield (relative to the overall size of the vehicle) also makes it more feasible to use active cooling without compromising performance as much.
Steering the rocket
The first stage of Nova, just like pretty much all other rockets, uses thrust vectoring to orient itself, where an engine tilts in a specific direction to change the angle of thrust. But because Nova’s second stage has 30 individually controlled thrust chambers, it uses a thrust differential steering method, allowing precise control by individually adjusting the throttle of each of the 30 thrusters.
Simple demonstration of thrust differential steering (ZenothKSP)
It also has a more common, but equally as interesting way of controlling itself during reentry. It uses a slightly skewed heat shield, where during reentry, it creates an asymmetrical aerodynamic force. By rolling the capsule there is one area of the heat shield that generates more force than the rest. For example, if the capsule rolls in a way so the heat shield extends more on the left side, it will produce a force pushing the vehicle to the left. This skewed heat shield and rolling maneuver provides very precise control over the capsule’s re-entry path.
Demonstration of capsule reentry with skewed heat shield (ZenothKSP)
S1E rocket engine
The first stage of Nova is powered by 7 Full Flow Staged Combustion Cycle rocket engines, currently named S1E. They started development of their first stage engine in November 2022, and only 18 months later, on June 5th 2024, they fired their first S1E engine. This is really impressive considering that Full Flow Staged Combustion has only been done twice before, and it is about as complicated as it gets when it comes to rocket propulsion.
First test fire of S1E (Stoke Space)
A full flow of each propellant, so liquified natural gas as fuel and liquid oxygen as oxidizer, flow through their own separate preburners, where they partially burn with a small amount of the opposite propellant. For example, in the fuel turbopump assembly, nearly all the fuel goes into the fuel preburner, along with a small amount of oxidizer to allow for combustion. This combustion produces a fuel-rich exhaust that powers the fuel turbine, which in turn drives the fuel turbopump. Similarly, in the oxidizer turbopump assembly, the oxidizer mixes with a small amount of fuel, creating an oxygen-rich exhaust that powers the oxidizer turbine and turbopump. After powering the turbopumps, the fuel-rich and oxygen-rich exhausts continue into the main combustion chamber, where they fully combust to produce thrust.
Schematic of Full Flow Staged Combustion (ZenothKSP)
So why does Stoke Space use Full Flow Staged Combustion? Because both the fuel and oxidizer enter the combustion chamber as gases, there is a gas-gas interaction inside the combustion chamber, which is more efficient than a liquid-liquid, or liquid-gas interaction. Full Flow Staged Combustion also allows for a higher mass flow through the turbine compared to other cycles, which means an increase in turbopump power and chamber pressure. And lastly, because of the big difference in fuel to oxidizer ratios in the preburners, the preburner exhaust temperature is lower than on other engines. This cooler exhaust reduces stress on the turbine blades, making them more durable and allowing them to be reused more often before requiring refurbishment.
Facilities
As of right now Nova is still in development and will be for the coming years. Stoke Space has a testing facility near Moses Lake, Washington where they test stuff like engines and flight systems, located about 3 hours from their main manufacturing facility in Kent. They have been designated historic Launch Complex 14 at Cape Canaveral Space Force Station, which is the same pad where John Glenn was launched to become the first American in orbit, and they have recently started transforming the pad to be compatible with Nova.
Stoke Space’s 2nd stage engine test stand near Moses Lake (Stoke Space)