US space startup Stoke Space is focusing its efforts on solving the single biggest remaining challenge in making space travel truly routine: creating a rapidly and fully reusable second stage rocket. While companies like SpaceX have mastered the recovery and reuse of the large first-stage booster, the upper stage, which reaches orbital speeds and faces extreme heat during re-entry, has remained a piece of expensive, disposable hardware. Stoke Space aims to change this with its Nova medium-lift launch vehicle, designed for 100% reusability. The ability to fly both stages repeatedly would lower launch costs drastically, making access to space affordable and quick.
Key Takeaways
- Stoke Space’s Nova rocket is designed to be 100% fully and rapidly reusable, targeting the tricky second stage.
- The second stage, called Andromeda, uses a unique actively cooled metallic heat shield integrated with its engine.
- The cooling system circulates liquid hydrogen (the rocket’s fuel) through the shield to absorb re-entry heat.
- This design avoids fragile ceramic tiles and allows for minimal refurbishment, aiming for a 24-hour turnaround between flights.
- Nova is a two-stage-to-orbit rocket, with a planned payload capacity of 3,000 kg to Low Earth Orbit (LEO) in its fully reusable configuration.
The second stage is crucial because it takes the rocket from the edge of space to the required high velocity for orbit. This higher speed means a much more demanding and fierier re-entry compared to the first stage. Traditional second stages burn up or are discarded in orbit. Stoke Space recognized that full reusability, where both stages can return and fly again with minimal preparation, is the only way to genuinely reduce the cost and manufacturing cadence of space launches.
The Andromeda Second Stage Solution
Stoke’s answer lies in the innovative design of its second stage, known as Andromeda. The stage features an integrated engine and heat shield system. Unlike conventional spacecraft shields that use ablative materials or brittle ceramic tiles which need frequent inspection and replacement, the Andromeda stage has a regeneratively cooled metallic heat shield.
This metallic shield is built into the base of the vehicle. During the intense heating of atmospheric re-entry, the rocket’s liquid hydrogen fuel is pumped through cooling channels embedded within the shield. Hydrogen has excellent heat capacity, meaning it absorbs the extreme heat and keeps the structure protected and cool. This active cooling method uses existing fuel flows, simplifying the overall system and reducing weight. The metal shield is designed to be durable and resilient, allowing it to survive re-entry and be ready for the next flight with minimal maintenance.
The Andromeda engine, which uses liquid hydrogen/liquid oxygen (hydrolox) propellant, is an expander-cycle engine with 24 individual thrust chambers arranged in a ring around the shield’s perimeter. This arrangement also helps create an aerospike-like effect, improving performance. Stoke Space successfully tested a full-scale prototype of this second stage, nicknamed ‘Hopper2,’ demonstrating vertical take-off, hovering, and controlled landing, a major step in validating the key technology.
The full Nova vehicle stands at 40.2 meters tall and has a diameter of 4.2 meters. The first stage will be powered by seven Zenith full-flow staged combustion engines, using methane/liquid oxygen (methalox) propellant, and will perform a propulsive return-to-launch-site landing. The combined system is designed to transform launch operations from bespoke manufacturing into an airline-like system. Stoke Space is targeting an orbital test flight for Nova by 2026.
Related FAQs
Q: What is the main barrier to fully reusable rockets today?
A: The biggest technical difficulty is making the second, or upper, stage fully reusable. This stage reaches orbital velocity, causing it to experience much higher re-entry speeds and heat loads than the first stage, which makes recovery and rapid reuse difficult.
Q: What is the Nova rocket’s payload capacity?
A: The Nova launch vehicle is designed to carry a payload of 3,000 kg to Low Earth Orbit (LEO) when operating in its fully reusable configuration.
Q: How does Stoke Space’s heat shield work?
A: Stoke Space uses an actively cooled metallic heat shield. It circulates the super-cold liquid hydrogen fuel from the rocket’s tanks through channels in the metal shield structure during re-entry. The hydrogen absorbs the intense heat, protecting the stage, and then is used to power the engine for the final landing burn.
Q: What is the expected turnaround time for the Nova rocket?
A: Stoke Space aims for a 24-hour turnaround time for the Nova rocket, meaning the entire vehicle (both stages) can be ready to launch again one day after landing.
Q: What fuel does the Nova rocket use?
A: The Nova rocket uses two different propellant combinations: the first stage uses methane and liquid oxygen (methalox), while the reusable second stage uses liquid hydrogen and liquid oxygen (hydrolox).
