Longshot Space Technology is developing a ground-based gun for hypersonic testing, with space launches as its eventual aim. The two uses require very different scales: the company’s current equipment accelerates projectiles on the ground, while a payload headed for space would need its own propulsion and a gun about 10 kilometers long.
Rockets leave little room for error, and only a small share of their weight makes it to orbit. Other proposed options include space elevators, centrifuges, and a chain hanging from a satellite to lift cargo from Earth. Blue Origin explored the chain idea before it appeared in a Neal Stephenson novel. Longshot is working on another alternative, an approach associated with Jules Verne: shooting a projectile into space.
The Alameda, California, startup was co-founded by CEO Mike Grace and CTO Nato Saichek and has raised about $20 million from venture investors. Grace says frontier-technology companies have to choose between novelty and taking on a hard problem: “you can build something that has a lot of novelty, or you can do something really hard. You don’t get to do both.”
As an example of scaling established technology, Grace cites SpaceX, which he says has “taken classically de-risked technology and scaled it aggressively.” Longshot intends to apply a similar approach to multi-injection guns. Developed for World War II and in research programs during the 1960s, these designs boost a projectile repeatedly as it travels through the barrel. Grace says Longshot’s effort follows the example of SpaceX’s use of NASA rocket research.
The company’s design shifts the work of a launch vehicle’s first stage to a reusable accelerator on the ground. A horizontal steel pipe has ports along its length fitted with high-pressure gas tanks. As a projectile passes through the barrel, the tanks fire in sequence at carefully timed moments, pushing it faster. Longshot says its system has so far reached Mach 4.
Longshot is testing a 70-foot-long gun with a six-inch diameter near Barstow, California, and says it can accelerate projectiles to near-hypersonic speeds. The company expects to begin firing a 140-foot-long gun with a 30-inch diameter at its Alameda test site soon. It is also preparing a 328-foot-long, 30-inch-diameter gun, with plans to extend it to about 3,000 feet. Longshot says the completed gun would be the largest on the planet and could launch 220-pound payloads at Mach 8.
The guns are intended both to demonstrate Longshot’s technology and to bring in revenue from hypersonic testing for the U.S. military, which has awarded the company several contracts. Grace has proposed placing a gun at a U.S. military installation such as Fort Bliss to help test the next generation of U.S. interceptors.
The gun does not have to point upward. Longshot’s projectile is a lifting body: its shape creates lift, allowing it to gain altitude aerodynamically after leaving the barrel. Grace says the system could also make hypersonic target practice much cheaper than using a $30 million target. “If you want to practice shooting down a Chinese or Russian hypersonic missile, wouldn’t it be nice not to pay $30 million for that?” he asks. “This is a way for half a million, a quarter of a million bucks, of doing hypersonic clay pigeons, throw them and shoot them down, and do it really fast and really cheap.”
Longshot’s ultimate aim is to send large payloads into space. The team believes it can scale its design to accelerate payloads to as much as five kilometers per second, or more than 11,000 mph. That speed could get a payload into space if it carried its own propulsion system and effectively acted as a rocket’s second stage.
A gun capable of reaching that performance would need to be 10 kilometers long, about six miles, and nearly 10 feet in diameter. Finding a site suitable for such a structure is one obstacle. “The hard part is not building the thing, it’s finding a place where they will let you build the thing,” Saichek jokes.
If Longshot realizes its vision, Grace says the system would be cheap to construct and fuel, and highly reusable. He puts the potential launch cost at $50 per kilogram, or about $22 per pound. The much-hyped orbital data center industry needs launch prices to fall to around $300 per kilogram to get off the ground, leaving Longshot plenty of room to offer a competitive price relative to that threshold. Spacecraft would need changes to suit the system’s form factor and conditions, but satellite operators would be willing to try it at that price, according to the article.
