Iterative improvement

Proudly presenting the SR-2c


This design is quite different from SR-2b. Instead of relying on two large RD-101 engine stages, the second stage is now powered by an engine that's part-way between the SR-1 and SR-2 engines offering 28.8kN of thrust in atmosphere.

Historical aside: In fact, the engine is based off an engine designed for use by rocket planes: The XLR11 used by the X-Plane project. We're re-purposing it here, but we'll probably also stick it to our plane as our new project after the SR-2.

The overall rocket has a significantly higher delta-v than the SR-2, easily capable of achieving 40% of that needed to get in to Earth orbit in fact! Delta-V is the 'main currency' of space flight and reflects a rocket's total change in velocity over time, a reflection of its overall capability. Our long-term goal is to get our delta-v up to 10,000dV, at which point we should be able to achieve a Low Earth Orbit of 2,000km.

I have also added launch towers to ensure it takes off straight upwards, giving it an advantage off the launch pad. The overall much lighter (only 10 tonnes!) design doesn't rely on any spin stabilisation for the first stage. Although it has a habit of veering off during the de-coupling stage, the second stage is light enough that it quickly self-stabilises on its fins just like the SR-1 did, with the assistance of just a small amount of spin.

Although it took a lot of thought to get it to this stage, the design is now believed to be quite stable and reliable, ready to break some records and take up a payload of insects.

Historical aside: The first biological payload sent in to space was a set of fruit flies, sent up on a (seized) V-2 rocket in 1947. They were recovered alive after breaking the Kármán line!

In fact, the largest issue with the design is that it's a little too efficient. When the rocket achieves 4,000dV the payload re-enters Earth's atmosphere too fast for our current late 1951 technology (remember, we're still using un-shielded steel!) and this often results in the payload being destroyed by the heat!

By intentionally reducing the fuel in each stage and adding an extra layer of 'ablative' steel shielding in the nose cone, I'm confident this design should be able to re-enter under typical conditions.


Even downscaled to keep the speed lower, the design should be capable of taking our biological payload up to 400km, vastly more than our previous rockets! No avionics are required and the tooling costs are much more reasonable than the hypothetical SR-2b design. Overall it's an objectively superior design in every respect, even if it did require quite a bit of iterative development to get to this stage.

With the money from its maiden flight, I hope to get enough to pay outright for the costs to kick-start the Y-Plane programme.

Next Post: There and back again, a fruit fly's tale




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