Hacker News Reader

Comment by spaceflunky | Hacker News Reader

> We're building our prototype now—and will fly late next year.

Will fly late next year? Where have I heard that one before...

A brand new advanced composite supersonic jet flying in a year's time? Color me skeptical. There are literally millions of things that need to be designed for this, and many of them will be bleeding edge. And this is from some tiny startup?

A line like that sets off some big flashing red lights for me. Either they're incompetent and have grossly underestimated the amount of work needed to complete this, or it's a scam.

Not quite. According to [1], what they'll be flying is actually a one-third-scale prototype, which I'd imagine is a lot easier to build. And they've already been going for two years.

The real issue that I'm not seeing addressed is capital. No investors listed anywhere.

[1] http://www.bloomberg.com/news/articles/2016-03-21/this-aeros...

EDIT: Forgot to actually include the link.

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.

So I've actually worked on a couple of aviation projects in career as a biz dev person. A usual development technique is to build at small scale and then work your way up.

The problem is that when you get closer to 1:1 scale, new always issues come up with bigger challenges. You solve one problem at 1:5 scale, only to realize that doesn't work at 1:3 and the whole thing needs to be redesigned from the ground up.

The annals of aviation history are littered with aircraft unable to move past 1:n scale.

Lockheed Skunkworks have actually built prototype jets in under 2 years from go ahead to first flight. The A-12 (predecessor to the SR-71) went from contract to first flight in just over 2 years.

Didn't Burt Rutan make a composite aircraft from design to first flight in a year back in the 80s?

Getting the aircraft certified and into production is where most of the actual expense is.

A company like this that manages to produce a supersonic flying scale model will probably have access to the capital required for those later steps.

Reply on news.ycombinator.com