The Kestrel at eight years: what we got right and what we would change

The Kestrel Light Shuttle first flew on 3 September 2179, and this autumn it turns eight. More than 600 have been built, they have flown an estimated 90 million kilometres between Earth orbit, Luna and L5, and the type has never had a fatal accident. I am proud of that record and of the team that earned it, but an anniversary is also a good time to be honest about what we would do differently.

What we got right was restraint. The Kestrel's original brief was a two-pilot shuttle carrying eight passengers and 6 tonnes over a 14 AU range for under 15 Mc. Every time someone wanted to add a feature, we asked whether it served that brief. The result was a 34-metre ship with methalox engines that any orbital depot can refuel, and a commissioning price that has crept only to 12.8 Mc today.

We also got maintenance right. The Kestrel was designed so that every line-replaceable unit could be swapped by a technician in a pressure suit in under 40 minutes. Operators routinely achieve 96 percent availability, and the average Kestrel spends fewer than nine days a year in the hangar.

What would we change? Three things:

• Fuel economy. At 9.5 tonnes per 100 AU, the Kestrel is thirsty by modern standards. Methalox was right for 2179 because it was available everywhere; a hybrid drive would make sense today.
• Cabin noise. Passengers consistently rate the ride as loud, and our acoustic damping was an afterthought.
• The flight deck. The original interface was designed for two pilots splitting workload equally. Modern autonomy means one pilot could manage most phases, and the second seat should be a supervisory role.

Those lessons are already showing up elsewhere. The Wren and the Sparrow Trainer both inherited the Kestrel's maintenance philosophy, and the next shuttle, currently in concept studies, will start from a single-pilot cockpit with an optional second seat.

I want to thank the operators who have flown Kestrels for eight years and sent us thousands of pages of feedback. Many of the best ideas in our current fleet started as a complaint written in a Kestrel logbook.