Comment by jandrese | Hacker News Reader

Comment by jandrese | Hacker News Reader

Parent Full thread

That link didn't make me feel much better. They're planning to "tweak an off the shelf engine for supersonic speed". When I hear off the shelf engines, I think turbofans, but no amount of tweaking is going to make a turbofan work at supersonic speeds. It's possible they can get some military grade afterburning turbojets from somewhere, but it's not something you can buy off of the shelf.

Their webpage has a bunch of guys standing around what looks like a Vietnam-era jet engine.

Also, if they're planning to have something flying in 20 months, they should be beyond the cardboard and plywood mockup phase of development.

The more I see about this company the more I think it's a scam.

For comparison, the Concorde took about 21 years to develop. Granted, it was a massive clusterfuck, but they also had to solve a lot of issues along the way.

> but no amount of tweaking is going to make a turbofan work at supersonic speeds

Sure they can. It's the inlet's job to slow the flow to subsonic. Turbofans have been used on supersonic military aircraft since the 1960's. Go read about intake ramps. Then learn about diverterless supersonic intakes.

You're yelling scam pretty loud for someone that clearly doesn't know basics of the topic area.

Edit: My guess is the engine they're standing in front of is a JT8 of some flavor, which have been heavily used by both military and commercial aircraft.

But those intakes don't work for free. You will encounter huge losses and drag penalties. And military jets aren't designed to fly 3500 miles supersonically the entire way. The vast majority of miltiary jets have a maximum supersonic time that can be measured in minutes.

This isn't quite so cut and dried: the ram effect can help or hurt depending on the exact context and numbers.

There are several 4th generation fighters with sustained supersonic cruise, as well as older aircraft like the B1. The basic technology has been around for decades. Nothing about the proposed supersonic small commuter jet is impossible from an engineering perspective, though aspects of it won't be _easy_, and it is entirely possible the business case doesn't work out.

I mostly replied above because of the categorical statement that supersonic flight with turbofans is impossible. The reality is that virtually all supersonic aircraft use engines with some bypass. The Concorde's engines oddly enough are one of the few zero bypass designs used in industry.

Reply on news.ycombinator.com