Re: [ERPS] This is one way to do it - Wonder it is works?

[Ian Woollard]

Henry Spencer wrote:

Unfortunately, a flyback booster almost certainly wants to cruise back at
subsonic speed.
Yes; I wasn't suggesting supersonic flight.

 Ramjets work poorly below Mach 1.
 

They're not that bad at about mach 0.85 or so, particularly for a point 
design which is all you'd need here.

Stir in the availability of turbofans off the shelf, and the desirability
of powered landings for operational transport vehicles,
Yes, but it's an unmanned flyback booster, not a transport vehicle.

and ramjets don't
look very attractive for this.
 

On the other side of the coin, the thrust:weight ratio is not that bad, 
you only need enough thrust to hold an altitude for a couple of hundred 
kilometers, and you may even be able to use it on the way up too (for a 
small amount of the flight envelope), they have no moving parts, they're 
more reliable, need much less maintenance, and are cheaper to build/buy 
than a turbojet.

I'm not saying they're theoretically as good as a turbojet; but quite a 
bit of the cost of a launch vehicle is in the purchase of the said 
launch vehicle and jets cost a whole lot more. Fuel is the cheap bit. 
I'd bet dollars to donuts that it's more cost effective in this case.

                                                         Henry Spencer
                                                      [EMAIL PROTECTED]
 

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