Randall Clague | 1 May 05:29 2003

Re: NASA views on nuclear propulsion

On Wed, 30 Apr 2003 15:59:01 -0700, Sawyer, Steven D. (PS, NE) 
<Steven.Sawyer <at> gene.GE.com> wrote:

> An interesting story and video on Project Prometheus with NASA views on
> nuclear propulsion ...
>
> http://www.msnbc.com/news/906920.asp?0dm=N22BT

Not really relevant to ERPS except as an example of the kind of shoddy 
reporting ERPS can expect when it achieves public visibility.

> The ability to explore planets beyond our solar system will require
> the use of space vehicles with nuclear-powered propulsion systems,
> NASA Administrator Sean O’Keefe said Tuesday.

Ya think?

The problem with this statement is that while it is true, it is not nearly 
sufficient.  It implies that nuclear-power propulsion systems will enable 
exploration of extrasolar planets - and unless you consider antimatter to 
be nuclear power, that simply isn't true.  Interstellar travel is millions 
of times more difficult than interplanetary travel.  Given that our batting 
average for interplanetary propulsion is only .661 (43 for 65), the 
prospects for interstellar travel look dim.  And O'Keefe is talking about 
exploring extrasolar planets?  Let's run a little exercise.

Exploring extrasolar planets means the probe has to be able to reach the 
nearest star with extrasolar planets, epsilon Eridani, within the working 
lifetime of the Principal Investigator.  Let's be generous and call that 40 
years.  eps Eri is 10.4 light years away, but let's be generous again and 
(Continue reading)

GDNordley | 1 May 22:53 2003
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Re: NASA views on nuclear propulsion


<< > The ability to explore planets beyond our solar system will require

> the use of space vehicles with nuclear-powered propulsion systems,

> NASA Administrator Sean O'Keefe said Tuesday.

Ya think?

 >>

I think the reporting of what O'Keefe said, is probably accurate.  His lack 
of understanding of science and technology is again on display--he's easy 
prey for mid-level empire builders with dumbed-down presentations of pet 
projects to push and turf to defend.   Direct nuclear propulsion systems, 
with exhaust velocities around 0.05c are generally inadequate for 
interstellar exploration -- unless you're willing to wait for decades to 
centuries for the data to come back.  (I'll waffle a little bit about the 
Alpha Cen. system, but no planets there yet.)  

One really wants to approach the speed of light, and that seems easiest with 
some form of beamed propulsion (photons, particles, or hybrid systems using 
both) wherein the vast majority of the propulsion system mass remains behind. 

The relevance to ERPS, I think, is to think about the powerful leverage of 
launch assist technologies for the Earth to orbit mission, some day.

--Best, Gerald
i.woollard | 2 May 03:24 2003

Re:[ERPS]NASA views on nuclear propulsion

"OK, so since our required delta-v is 15 times our exhaust velocity, then our mass ratio needs to be e15. 
That's 3.27 million.  Expressed as a mass fraction, that's 0.9999997.  I think the best humans have done in a
flight vehicle so far is, what, about 0.95?"

No, much better. Careful here. You're comparing the mass fraction of a STAGE with the mass fraction of a
vehicle. 0.95 is good for a launch stage, but a space stage could probably manage more like 0.99 IMHO. After
all there's no gravity so the engines can be relatively small, and the tankage may well dominate the mass fraction.

Also, consider drop tanks; if your tank weighs even 5% of the mass of the propellents, but you toss it as soon
as it is empty; then the tank just decreases the effective impulse of the fuel in the tank by 5%. (Approximately)

In deep space it seems quite plausible to do that, and there's no emergency if a tank doesn't fall off when it
should, you go along with a crowbar later sometime in the next 10 years...)

So the mass fraction of the vehicle is still in the millions, but the effective ISP is about 95% of the real
exhaust velocity.

"A mass fraction of 0.9999997 means that if you used as much hydrogen fuel as the Space Shuttle, your tank,
engine, payload, power system, and communications system, all together, could weigh just over an ounce."

Yes, you'd have to start with a vehicle much bigger than the Shuttle if you're going interstellar.
(Actually, I was surprised how small the shuttle really is when I saw one). Anyway, if you're mining the
materials for your vehicle from off planet (e.g. asteroids). I don't see that this is a very big problem;
but it's certainly a big vehicle ;-)

This is all assuming we have nuclear fusion, but the scientists currently assure us that we will have that in
under 30 years time, which is good because 30 years ago it was 50 years away, so the series is converging ;-)

Anyway, I agree that ERPS probably shouldn't be studying interstellar travel at this point.
(Continue reading)

Thomas J. Williams | 2 May 04:55 2003

RE: Paraffin Rocket

Folks,

Another article with a bit more detail on the paraffin hybrid (reported by
AW&ST) can be found at:
http://thomasc.stanford.edu/aw50_54.pdf

It mentions adding Aluminum to the wax when using it with peroxide (although
I'm not sure what
that would buy if you are running it with decomposed HTP).

You might be able to set it up almost like an add-on after-burner for a
mono-propellant engine.

-Tom Williams

--__--__--

> From: Michael Wallis <mwallis <at> Ceres.wallis.com>
> To: erps-list <at> lists.erps.org (ERPS Main List)
> Date: Tue, 29 Apr 2003 17:53:09 -0700 (PDT)
> Subject: [ERPS] Paraffin Rocket
>
> Hi ...
>
> Many years ago a few ERPS members helped with a conceptual design for
> a paraffin wax rocket engine, using high temperature HTP exhaust to
> melt the wax. We thought it was a funny idea for a high density
> propellant. Little did we know that it wasn't so weird:
>
> 	http://www.sciencenews.org/20030322/bob9.asp
(Continue reading)

Michael Wallis | 2 May 18:40 2003

E.R.P.S. Annual Meeting - 03 May 2003

The Experimental Rocket Propulsion Soociety will hold it's Annual
Meeting and Elections this coming Saturday. The meeting is open to all
members and interested parties. The meeting will also see the election
of Directors and Officers for 2003. Voting on Elections is limited to
the Participating Members of the Society.

=====
Annual Meeting
Sat 03 May 2003 - 1:00 pm  <at>  CDI

C D International Technology, Inc.
473 Sapena Court, #24, 
Santa Clara, Ca 95054

Agenda:
-------
Call to Order

Chairman's Remarks
State of the Society - President
Financial Report - Treasurer

Election of Directors - 5 seats
  - Selection of Board Chairman

Election of Officers
  - President
  - Vice President
  - Secretary
  - Treasurer
(Continue reading)

Alex Fraser | 3 May 05:35 2003
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CAD

    Just got an evaluation copy of  Autodesk Inventor. I hope I can get 
good enough to do some 3D rocket stuff. It is pretty groovy.
    How goes the TurboCAD? Did folks go with the version 9 upgrade offer?

--

-- 
>>>>>>>>>>>>>>>>----<<<<<<<<<<<<<<<<<
........ Alex Fraser  N3DER .........
......... beatnic <at> comcast.net .......
[~]_>^</\-[~]_>^</\-[~]_>^</\-[~]_>^<
GDNordley | 3 May 08:38 2003
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Interstellar Rockets


<<OK, so since our required delta-v is 15 times our exhaust velocity, then 
our mass ratio needs to be e15.  That's 3.27 million...>>
Some years ago, I spent probably more time than I should have trying to make 
a very large mass ratio interstellar rocket work (on paper, at least).  One 
has to keep in mind that the figure of merit is time to destination, not 
maximum velocity.  In other words, one needs some decent acceleration.  This 
means a lot of engine mass, which at first look is not compatible with a high 
mass ratio.  However, if as one builds up velocity and loses mass, one 
doesn't need as many engines.  The unneeded engines can be discarded or 
ground up and used as reaction mass. ;-).   Still, mass ratios in the 
millions are difficult...
--Best, Gerald
Donald Qualls | 3 May 16:24 2003
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Re: Interstellar Rockets

GDNordley <at> aol.com wrote:
> <<OK, so since our required delta-v is 15 times our exhaust velocity, then 
> our mass ratio needs to be e15.  That's 3.27 million...>>
> Some years ago, I spent probably more time than I should have trying to make 
> a very large mass ratio interstellar rocket work (on paper, at least).  One 
> has to keep in mind that the figure of merit is time to destination, not 
> maximum velocity.  In other words, one needs some decent acceleration.  This 
> means a lot of engine mass, which at first look is not compatible with a high 
> mass ratio.  However, if as one builds up velocity and loses mass, one 
> doesn't need as many engines.  The unneeded engines can be discarded or 
> ground up and used as reaction mass. ;-).   Still, mass ratios in the 
> millions are difficult...

I'm not sure I see the advantage of high initial acceleration.  At least 
over interplanetary distances, accelerations of a few tens of milligees 
and constant boost win over initial high acceleration (of the sort 
characteristic of conventional chemical rockets) and Hohmann transfer 
coasting.  ISTM that the same would be true of an interstellar rocket, 
given only that the peak velocity at turnover is allowed to be much 
higher than the coast speed for the other design.

I guess the limitation here is that you need still higher mass ratio to 
get the higher turnover velocity, which would none the less reduce trip 
time; you might get stuck with a boost-and-coast scheme if you can (for 
some reason) build a ship with a mass ratio of 10 million, but can't 
build to 25 million.

--

-- 
What you own is your own kingdom, what you do is your own glory.
What you love is your own power, and what you live is your own story.
(Continue reading)

Jonathan Andrew Goff | 3 May 19:57 2003
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CAD Stuff

Hey guys,

I have access to all sorts of CAD, FEA, and CFD
programs here at school (Solidworks, CATIA, PRO/E,
Unigraphix, Fluent, Ansys, etc.)

I'm out here in Utah, but if you have some CAD
work I could help out on, I'd be more than happy
to help.

~Jonathan Goff
Pierce Nichols | 4 May 03:30 2003
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Sparger Status

The Good News:

         We mounted the sparger column and air pump on its new stand, and 
hooked everything up. As a result, the sparger is now functional. We ran a 
quick water test to verify function, and then it was time to go home. Sean 
and I will be going up tomorrow to run a full set of tests to characterize 
its performance, and maybe even make some peroxide. Yay us. Kevin's idea 
about the screen was very good -- it suppresses nearly all the water spray 
out of the top. However, there is still enough that I won't approach closer 
than 20 ft to it without a hazmat suit when it's running peroxide. The 
water coming out the top feels markedly more humid than ambient, which I 
consider to be a good sign that it's doing something. I'll see if I can 
take some pictures tomorrow to show off.

The Bad News:

         There is something wrong with the Honda generator. Neither Sean 
nor I could get it to even kick. I have it with me, and if there are no 
objections, I will take it to the Honda dealer in town on Monday to see if 
I can get it fixed. I hope there will be no issues with our unathorized 
mods, which have no doubt voided the warranty. We were able to work today 
using an extension cord from Chuck's generator. I plan to do the same 
tomorrow.

         -p

Mars or Bust!
www.marssociety.com

Gmane