[AR] Re: 500,000 tons OFF TOPIC

  • From: Keith Henson <hkeithhenson@xxxxxxxxx>
  • To: arocket@xxxxxxxxxxxxx
  • Date: Thu, 10 Apr 2014 08:04:44 -0700

Ian is exactly right on this post.  Laser propulsion is just awful
till you reach about 1/4 of the velocity to orbit.

On Thu, Apr 10, 2014 at 7:39 AM, Ian Woollard <ian.woollard@xxxxxxxxx> wrote:
> It's because rockets are highly inefficient at "low" speed (i.e. below about
> Mach 7) while hydrogen upper stages (even laser powered ones) have low GLOW
> but don't have SSTO delta-v on their own.
>
> And it's not just a 'little more fuel' it's all the hardware to carry and
> push that fuel around that you have to carry to orbit. And really 80% of the
> thrust of Skylon is nitrogen; Skylon is a way to use nitrogen for
> propulsion.
>
>
> On 10 April 2014 09:37, Jake Anderson <jake@xxxxxxxxxxxxxxx> wrote:
>>
>> I think at a fundamental level, we aren't seeing what air breathing brings
>> to the table over using a standard rocket.
>> I mean sure the laser boosted thing is nice but why do you need to breathe
>> air with your beamed power application, it just makes things more complex vs
>> adding a little more fuel.
>>
>> The pro's and cons of HTHL vs something else are a separate issue but not
>> one that would be insurmountable.
>>
>>
>> On 10/04/14 15:52, Keith Henson wrote:
>>>
>>> On Wed, Apr 9, 2014 at 3:09 PM, Monroe L. King Jr.
>>> <monroe@xxxxxxxxxxxxxxxxxx> wrote:
>>>>
>>>>   I only need to be right twice a day to make progress.
>>>>
>>>>   There is no sense arguing with you guy's I guess you have it all
>>>> figured out.
>>>
>>> Ah, how I wish I had it figured out.
>>>
>>> Which bring us around to what amateur rockets are about.
>>>
>>> It is fundamentally a way to have fun.  A reason to make things that
>>> go whoosh, or sometimes BANG and sometimes whoosh *and* BANG.  I had a
>>> run with amateur rockets when I was a kid, built and static fired a
>>> liquid fueled rocket engine when I was in the ninth grade, made ZnS
>>> rockets in high school.  Can post pictures of the crashed remains of
>>> one that went to 7200 feet.  *Might* be able to find the liquid rocket
>>> engine.
>>>
>>> But besides the fun, it's where I got my first appreciation for
>>> exhaust velocity.  Worked out what it would take to put a ton in orbit
>>> with ZnS (a rotten exhaust velocity if ever there was one).  I
>>> reworked the problem recently and we got it right back in the late
>>> 50s.  The first stage of a one ton orbital ZnS rocket would cover the
>>> entire state of Arizona.
>>>
>>> snip
>>>
>>>>   I hope Skylon flies
>>>
>>> Me too.  I am hanging the entire power satellite economic model on a
>>> laser boosted Skylon.  Reaction Engines people think this is a fairly
>>> nifty idea.  No wonder, it's an extension of their stock in trade,
>>> high exhaust velocity.  I met with the lot of them in Culham a and a
>>> half year ago.  Don't hesitate to ask any of them, including Alan
>>> Bond, what they think of a laser boosted, hydrogen only variation on
>>> Skylon.
>>>
>>> snip
>>>
>>>>   I do wish arocket would help out the amateurs and more discussions
>>>> where based on real work being done by amateurs. This really could be a
>>>> great place to make progress for everyone as it is these day's I can't
>>>> even post relevant to amateur rocket progress.
>>>>
>>>>   There is nothing "new" in AMATEUR rocketry.
>>>
>>> That's a sad fact.  Short of changing the physical constants of the
>>> universe or nanotechnology we can't do anything about it.
>>>
>>> If you want to do serious things in space, amateur won't do it.
>>>
>>> On the other hand, this list is one of the very few places on the net
>>> where you can talk about exhaust velocity and people know what you are
>>> talking about.
>>>
>>> Keith Henson
>>>
>>> http://en.wikipedia.org/wiki/L5_Society
>>>
>>> PS.  The Firefox browser on gmail highlight misspelled words for me.
>>> Without it, my spelling is no better than yours.
>>>
>>
>>
>
>
>
> --
> -Ian Woollard

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