To Brian

[T.L.G.vanderLinden@student.utwente.nl (Timothy van der Linden)]

Hi Brian,

My name is Timothy sometimes its Tim, whatever I feel like. If you like to
read some info about me look at my humble internet-site:

http://www.cpedu.rug.nl/~N0642983/personal.html

I have the habit to comment a lot and write less myself, simply because it
is hard to figure out some well working idea. Others often try but fail
after a while (not always ;) )

By the way Steve and I have an official nickname: "reknown throwers of icewater"
Kevin, how is you snowball ship doing?

>What does Cc mean anyway?

Carbon Copy it's derived from the good old days where they didn't have
E-mail and Xerox-machines.

>Thanks for responding to my first ever e-mail Kelly!  For the group's 
>information, I'm a junior pre-med biochemistry major at Oklahoma Christian 
>University of Science and Arts (it's a long name, I know) who hates the math 
>aspect of most anything but has seen too many Star Trek and Babylon 5 
>episodes to not be interested in LIT's starship design project.

Hmmm, you don't like math, then try not to read  :)

http://www.cpedu.rug.nl/~N0642983/calc.txt

>If this system involves power beaming, then there are going to be some
>serious losses in energy during the transfer.

Why would there be serious losses? It is a non diverging PARALLEL beam!

>HERE COMES ASCII ART :-)

It really looks like garbage, are you using a proportional spaced font? If
so try using a fixed sized font...
I haven't been able to get it ungarbled...

>I'm posting a BMP file of this idea right here just to see if it works. 
>Should be easier on the readers' sanity as I've heard complaints about this 
>somewhat limited artform.  How's the color?

The colour is fine, but never sent a 400kb bmp file again. ;) (My
mail-deamon complained that it took too long, so I could start over again)

The small mirror should not be concave (hollow) but convex (spherical) !

>Unfortunately, some power would be lost as it hit the secondary mirror (we 
>could make it one-way transparant if it were glass-like) and there will 
>certainly be losses due to irregularities in the mirror's surface and the 
>reflective material (silver is the best I can think of and that ain't 
>cheap).  The two would have to be connected as well to prevent any net 
>movement.

We are talking about micro waves, not visible light, so comparing with
ordinary mirrors and lenses has no use.

>Zubrin suggested that the particle stream be 
>neutral on the way to the magsail and that a laser carried on board could be 
>used to ionize it.  I would suggest using a laser that was NOT on board 
>because, as someone pointed out in ARC29, it would take a terawatt to ionize 
>100 sq. meters, not accounting for conversion efficiencies of energy into a 
>photon beam.

Why not use the beam alone instead of first beaming particles and then a
maser beam to ionize them. Also tapping the magnetic field would probably
have a very bad efficiency.

>I know that I am jumping from topic to topic here.  Its just that I've got a 
>lot on my mind that I want to get to you guys before I have to face my 
>Calculus homework.  By the way, you may be wondering where we are getting 
>the power for these propulsion designs.

No, we aren't wondering any more... We have given up hope, after going
through all possibilities.

>From the billions of 10 kilometer 
>square power stations out between Mercury and Venus, of course.

Indeed, about 1E12 m^2 or a billion 1 square kilomtres. What you probably
haven't thought of is that the same solar-radiation they capture also pushes
them away. And it is not neglectable! (It is bigger than the momentum our
spaceship has after accelerating) There have been some ideas to overcome
this problem, but they don't make it easier.

>Switching gears here, I was going over some information on the Deadalus 
>probe in a book called "Bound for the Stars" by S.J. and B. Adleman. 
> Anyway, the book said that the design was supposed to have a 15 to 1 fuel 
>to ship ratio that would get a 500 ton payload to just over .10c.  Using 
>that as the working number to beat, and knowing that the probe uses greater 
>than twenty-thousand tons of 3He (not exactly a common isotope), I tried 
>figure out how we could make that monster more fuel efficient.  The ideal 
>scheme would be to launch the fuel from Sol to the ship.  Or better yet, to 
>launch the ship to the fuel that is already on route.  Better still, 
>perhaps, do both.

Actually the ratio could be a lot better say 1:4 although no-one has
confirmed my number yet.
By the way we like using the scientific exponential notation: 10 tons = 1E4 kg
This is because sometimes the use of million and billion is not completely
clear and it makes comparing easier also.
5E5 kg is too little, we are talking about 2E9 kg or so, maybe a bit less
but I think that 1E7 kg is the absolute minimum.

>Anyway, the first tanker will actually have to carry enough fuel 
>to slow the ship as much as .1c, but thems is the breaks (I actually made a 
>semi-descent pun without meaning to).  This first tanker will also be 
>traveling only as fast as it can slow the starship to a full stop at the 
>next gas station in Tau Ceti's Kupier belt.
>
>The other smaller tankers will be launched during the appropriate windows 
>that will let them reach a position along the flight path that allow a 
>starship to catch up with them, find them in deep space via the homing 
>beacons, dock with them, and finally use their fuel to slow to the speed of 
>the next tanker and repeat the process.  This means that the overall 
>deceleration phase will be fairly lengthy.

Ha, this was my idea, we discussed it and guess what, it is discarded for
two reasons:
- To get the slowest tank at TC would take at least 100 years, too long for
any project.
- The time and place precision needed by the decel-track would not be feasable.

>By the way, the whole shielding problem is still of some concern to me.  How 
>much do we really need when flying at relatavistic speeds?  I think that we 
>should should pray to God that he doesn't put a lot of little paint flecks 
>sized particles between us and the stars or else our ship will run into them 
>and they will cause dents way bigger than seen on the space shuttle window. 
> One of "Bound for the Stars" suggestions for protection against smaller 
>debris was to put a dust cloud/bag of some sort ahead of the ship.  It would 
>act like a forward atmospheric shield.

I'm of the opinion that a solid shield is better than a gassious one. Simply
because it stays where it is and doesn't involve elaborate ice-gas shooting
cannons. It has been suggested to use a simple ice shield (not necessary
water-ice), it could be more easely renewed and may work well.

>Back to weight efficiency in the ship's design.  If the magsail is big 
>enough to effect any sort of deceleration by using the interstellar ionized 
>gas, then we should turn the ship around.  To do it, we fold the sail like 
>an umbrella, turn, and redeploy it.

Ionize interstellar gas, you are talking about it as if you could see it,
the best guesses are that the there is too few interstellar dust. Only a
ramscoop with a 1000 km radius may be enough to make some significant use of it.
I still have a hard time imagining how a magsail could work efficient,
magnetic fields have the peculiarity to be not very bundled.

>Whatever kind of deceleration it 
>produces will probably go virtually unnoticed by the crew and may be 
>compensated for in how we rotate our habitat for artificial gravity and or 
>by how it is laid out internally.   Exactly how we want to produce 
>artificial gravity will be determined in a later discusion.

We use engine thrust and centrifugal forces for gravity, there are no other
known possibilities.

>The only viable 
>solution that I can come up with to keep the shielding costs from getting 
>too far out of control is to use fuel/reaction mass as shielding.  Also we 
>could send some fuel/reaction mass/shielding after the ship.  This would 
>require putting an extra engine on either the fed express tanker or the 
>starship.

The problem with using fuel/reaction mass as shielding is that you have to
carry that fuel, if you want to get over a minimum speed of 0.3 c it is
impossible to push the fuel.

>For the cruising phase of the flight, we can afford to make a habitat that 
>is spacous and comfortable.  As soon as we want to slow down, however, we'll 
>have to stuff the crew into a collection of cramped, space economized, 
>modularized, trailer car-like habitats that fit into the cargo bay of the 
>space shuttles that we'll use to explore planet surfaces.

Too bad, we will be accelerating and decelerting all the time, so there is
no cruising phase period. And why would you make the ship bigger than
needed, acceleration takes energy too you know.

>This deceleration 
>storm shelter complex will be much easier to shield and, after we jetison 
>(how do you spell that word?) the cruising hab, will drop the ship weight by 
>tens if not hundreds of thousands of precious tons because the fuel that was 
>formerly shielding for our interstellar space hotel will then be used to 
>slow the ship to reach the first tanker drone.

(Wow a sentence of five lines with two commas)
After having thrown away the biggest part of your ship, how are you going to
return?

>You've probably noticed that I don't hold out much hope for getting our crew 
>back to Sol in their life-times.  Over the last few days I've come up with a 
>mission plan called for a starship named U.S.S. LEGACY.  It is to be the 
>pioneering manned starship of a colonization effort.  Other ships like the 
>U.S.S. HERITAGE will follow but that's my little fantasy.  For now I'll play 
>with the ASIMOV.

Ah thats why you throw away your ship. Makes me wonder how you want to camp
in the TC-system. Maybe you should have a long talk with Kelly...

By the way you have the name spelled wrong, it should be E.S. LEGACY it is a
European efford you know. ;)

>It is late and I need to do Calc.  I imagine that someone has come upon 
>these ideas long before me but I hope that what I've written has helped to 
>refocus some thoughts (II Peter 1:13 I think it is right to refresh your 
>memory as long as I live in the tent of this body). Thanks for taking the 
>time to read This, My Core Dump.

I not only read it, but even commented it...

>I invite comments to be sent by bus, plane, train, automobile, phone, mail
>or e-mail.

Don't you have a fax? :)


Timothy