A Space & astronomy forum. SpaceBanter.com

Go Back   Home » SpaceBanter.com forum » Space Science » Technology
Site Map Home Authors List Search Today's Posts Mark Forums Read Web Partners

SSTO propulsion overview



 
 
Thread Tools Display Modes
  #1  
Old January 13th 04, 02:48 AM
Henry Spencer
external usenet poster
 
Posts: n/a
Default SSTO propulsion overview

Catching up on some unread journals, I note that the March/April 2003
issue of JBIS has a very interesting paper: "A comparison of propulsion
concepts for SSTO reusable launchers", by Richard Varvill and Alan Bond.
While the authors have a mild case of hydrogen religion -- non-hydrogen
rockets are never mentioned -- and they obviously have their own axe to
grind, they generally give a good overview of the alternatives, including
why scramjets are such a lousy idea for space launch.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |
  #2  
Old January 14th 04, 02:57 AM
James Graves
external usenet poster
 
Posts: n/a
Default SSTO propulsion overview

Henry Spencer wrote:

Catching up on some unread journals, I note that the March/April 2003
issue of JBIS has a very interesting paper: "A comparison of propulsion
concepts for SSTO reusable launchers", by Richard Varvill and Alan Bond.
While the authors have a mild case of hydrogen religion -- non-hydrogen
rockets are never mentioned -- and they obviously have their own axe to
grind, they generally give a good overview of the alternatives, including
why scramjets are such a lousy idea for space launch.


This is all my opinion, of course...

After reading this newsgroup for a while, I have come to the conclusion
that any type of air-breathing for orbital launch is a waste of time
and money. Turbojets, scramjets, whatever. It just makes getting into
orbit harder, not easier.

The only exception to this is an aircraft carrier 1st stage. There are
some advantages to high altitude launch (less altitude compensation
needed for your rocket nozzle, for example), and it can give you a lot
of flexibility with launch site location. But that's the only
exception in my view.

I just can't understand why so much time and research dollars are being
spent on hypersonic research. If you want to get into orbit, you want
to get _out_ of the atmosphere as soon as possible. It is completely
counter-intuitive to try and gain lots of velocity while still inside
the atmosphere, where you are subject to drag (inefficiency) and heating
(exotic materials and/or cooling systems needed).

While this is drifting off-topic for this newsgroup, can someone explain
to me why so many in the aero/astro field still think hypersonics for
orbital launch are a good idea?

And are hypersonics a good idea for anything at all?

James Graves


  #4  
Old January 15th 04, 08:53 PM
Henry Spencer
external usenet poster
 
Posts: n/a
Default SSTO propulsion overview

In article ,
James Graves wrote:
...any type of air-breathing for orbital launch is a waste of time
and money. Turbojets, scramjets, whatever. It just makes getting into
orbit harder, not easier.
The only exception to this is an aircraft carrier 1st stage...


I'm inclined to say that the jury is still out on LACE and its relatives
(such as Alan Bond's concepts) and on things like the original Roton,
which airbreathe a little bit at the start of a largely rocket-powered
ascent. The idea is plausible; what remains unproven is that it's any
better than a pure rocket. I wouldn't build one myself, but wouldn't
exclude the possibility of success that way.

While this is drifting off-topic for this newsgroup, can someone explain
to me why so many in the aero/astro field still think hypersonics for
orbital launch are a good idea?


To some extent this is a lingering echo of the idea that spaceships are,
or *should be*, just especially high-performance aircraft. There has
never been any very strong justification for this belief, but it remains
an article of faith for many from the "aero" side of aerospace.

And to some extent, it's pure public-relations hype, the result of the
hypersonics people -- who have been largely rejected by the aero side of
the house -- trying to find funding from the space side (which has long
been the rich side of the family).

And are hypersonics a good idea for anything at all?


For high-speed cruise within the atmosphere -- assuming you have some
urgent reason to want to do that -- they look promising. But they have
nothing much to do with spaceflight.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |
  #5  
Old January 16th 04, 02:50 AM
Joann Evans
external usenet poster
 
Posts: n/a
Default SSTO propulsion overview

James Graves wrote:

Henry Spencer wrote:

Catching up on some unread journals, I note that the March/April 2003
issue of JBIS has a very interesting paper: "A comparison of propulsion
concepts for SSTO reusable launchers", by Richard Varvill and Alan Bond.
While the authors have a mild case of hydrogen religion -- non-hydrogen
rockets are never mentioned -- and they obviously have their own axe to
grind, they generally give a good overview of the alternatives, including
why scramjets are such a lousy idea for space launch.


This is all my opinion, of course...

After reading this newsgroup for a while, I have come to the conclusion
that any type of air-breathing for orbital launch is a waste of time
and money. Turbojets, scramjets, whatever. It just makes getting into
orbit harder, not easier.

The only exception to this is an aircraft carrier 1st stage. There are
some advantages to high altitude launch (less altitude compensation
needed for your rocket nozzle, for example), and it can give you a lot
of flexibility with launch site location. But that's the only
exception in my view.

I just can't understand why so much time and research dollars are being
spent on hypersonic research. If you want to get into orbit, you want
to get _out_ of the atmosphere as soon as possible. It is completely
counter-intuitive to try and gain lots of velocity while still inside
the atmosphere, where you are subject to drag (inefficiency) and heating
(exotic materials and/or cooling systems needed).

While this is drifting off-topic for this newsgroup, can someone explain
to me why so many in the aero/astro field still think hypersonics for
orbital launch are a good idea?


"If the only tool you have is a hammer, every problem looks like a
nail."

And to the less technically inclined, there's the carrot of not
carrying your oxidizer along. The price, of course, is taking it in at
increasing Mach numbers, and the drag imposed thereby, likely a heavier
engine for the same thrust, major thermal issues, etc. Everything you
said, and then some.

And LOX is cheap.

And are hypersonics a good idea for anything at all?


If all you *want* is high-altitude, hypersonic cruise (as opposed to
accelerationg to orbital velocity), sure. Recon, *perhaps* commercial
flights depending on the economics, etc. And perhaps expendable
hypersonic weapons.

But airbreathing to orbit, while it might yet be acheived, will be
only a niche application. Most access to LEO will be with rockets,
until/unless 'beanstalks' can be done, and even those will not
completely replace independent spacecraft.

James Graves



--

You know what to remove, to reply....
  #10  
Old January 24th 04, 02:46 PM
Azt28
external usenet poster
 
Posts: n/a
Default SSTO propulsion overview



And are hypersonics a good idea for anything at all?


For high-speed cruise within the atmosphere -- assuming you have some
urgent reason to want to do that -- they look promising. But they have
nothing much to do with spaceflight.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |


I think the sonic boom forbids any hypersonics aircraft service. If you want
such a possibility, the only practical solution is going out of the atmosphere
for most of the trip, so you get back to the rocket solution even if there is
no space travel or orbital capabilitiy. So I don't see any use for "hyper"
whatever the intended use.

Yvan Bozzonetti.
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
A revolutionary propulsion system asps Space Shuttle 49 December 21st 03 10:25 PM
Rudolphi Named NASA Space Shuttle Propulsion Manager Ron Baalke Space Shuttle 1 November 18th 03 04:16 PM
Rudolphi Named NASA Space Shuttle Propulsion Manager Ron Baalke Space Station 1 November 18th 03 04:16 PM
Ion Engine Records No Tuneups, No Problems Ron Baalke Technology 3 July 31st 03 10:03 AM
Accelerator Turbojet for SSTO johnhare Technology 0 July 9th 03 10:15 AM


All times are GMT +1. The time now is 03:59 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 SpaceBanter.com.
The comments are property of their posters.