Key points
- Longshot Space is building a 10-15 km hydrogen gun to launch payloads for under $100 per kilogram, versus Falcon 9's $5,000-$7,000.
- It builds with pipeline mild steel, concrete, and a $5 homemade feedthrough, rejecting a $5bn aerospace cost estimate.
- Gerald Bull's HARP fired cubesat-sized masses to orbital altitudes for $5,000 a shot, but SpaceX's cost focus now makes the market.
Longshot Space bets a 15 kilometre gun can undercut rockets
Longshot Space is betting the cheapest route to orbit is a gun. Gas expansion alone tops out near 2.5 kilometres per second, so the company pops burst discs in sequence down a 10 to 15 kilometre barrel, buying speed with length instead of propellant. HARP proved the physics in the 1960s and found no market, but SpaceX made launch cost matter. Longshot aims to undercut rockets by an order of magnitude using pipeline steel and $5 parts.
Takeaways
- Gas acceleration caps near 2.5 kilometres per second. Hydrogen's speed of sound is 1,270 metres per second, and a projectile pushed from behind reaches about twice that. Beyond it the pressure drops below 100 psi, so the barrel must run 10 to 15 kilometres to reach orbital speed.
- Burst discs fire in sequence to re-accelerate. The barrel is lined with pressure vessels charged with hydrogen at 1,000 psi. As the projectile passes each set at eight and a half kilometres per second, burst discs pop and more gas floods in behind it. A capacitor bank opens them in ten microseconds.
- Longshot targets under $100 per kilogram. Falcon 9 sells for $5,000 to $7,000 per kilogram and a future Starship lands near $1,000. Longshot targets under $100, with cofounder Mike quoting $10, and at $50 a kilogram space freight would cost twice what it costs to reach Europe.
- Longshot is an infrastructure project disguised as aerospace. Longshot buys mild steel and concrete from the pipeline industry and ignores the Space Mission Analysis and Design estimate of $5bn. Its power feedthrough carries 100,000 amps into a 1,000 psi vessel and was built from a one-inch NPT fitting and epoxy for $5.
- HARP proved the shot but found no buyers. Gerald Bull fired cubesat-sized masses to orbital altitudes for $5,000 a shot in the 1960s and 1970s with his Martlet rocket. There were no cubesats and no commercial space industry, so nobody bought. SpaceX later made cost per kilogram matter.
- A fixed barrel means a fixed orbit. A 10 to 15 kilometre gun cannot change its angle, so unlike a rocket it launches into one orbit and the customer has to fit. Longshot's space tug then takes the satellite to its chosen orbit in about fifteen minutes using chemical propulsion.
Selling a giant gun to investors
- Mike made hundreds of calls and got rejected for hours and weeks. Investors cared either about short-term weapon applications or about space launch, and the company's timeline outran their investment horizon.
- Early investors did less technical diligence than Nato expected. A 300-foot concrete tunnel with the world's largest gun inside is a better demo than a B2B SaaS dashboard.