[ExI] darpa's notion of using a retrofitted fighter jet to launch payloads

spike spike66 at att.net
Mon Feb 9 21:18:58 UTC 2015

-----Original Message-----
From: extropy-chat [mailto:extropy-chat-bounces at lists.extropy.org] On Behalf
Of BillK
Sent: Monday, February 09, 2015 12:10 PM
To: ExI chat list
Subject: Re: [ExI] darpa's notion of using a retrofitted fighter jet to
launch payloads

On 9 February 2015 at 19:13, justin corwin  wrote:
> I don't think I've ever seen a setup with engines mounted so high on 
> the fuselage, is there an engine/reference design that could be used for
> The artist seemed to have some very specific details one wouldn't just 
> assume.

It is a new design for small rockets launched from aircraft.

There is a good review here:
>...Boeing plans to take a unique approach with the ALASA launch vehicle
that is also intended to lower complexity and thus costs. The rocket will be
powered by a monopropellant: a combination of nitrous oxide and acetelyene,
mixed together in the same propellant tank and "slightly chilled" below room
temperature, Clapp said. That propellant choice offers simplicity as well as
a specific impluse "not far off"
from LOX and RP-1. "That's kind of a big deal," he said. "In general, it's a
dramatic simplification of the complexity of a rocket vehicle."

>...The rocket's design is also unusual, mounting four engines just below
the payload on the vehicle. The engines are used for the first and second
stages of the rocket, with propellant tanks below the engines dropping away
when exhausted. This approach avoids the expense and complexity of separate
sets of engines for the first two stages.


Cool thanks BillK.  I should have read this before I wrote the previous.
The Booeing boys are thinking the same thing I did: lose some cost by using
the same nozzles all the way up.  If you go that route, your penalty for
acetylene/nitrous really isn't all that much, because your nozzles are
forced smaller anyway, so you under-expand the exhaust, so you wouldn't get
full advantage of LOX/kerosene engines, and... you also get a small
advantage in higher fuel/oxidizer density with acetylene/nitrous rockets.
So this all makes sense to me and I welcome the day.  Reason:
government-funded rockets are always so very no-compromise on performance,
or performance at the expense of everything, specifically, expense.
Government-funded rockets are too expensive.  We have long known that cost
can come down if we accept lower performance.


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