The scale of a mass driver payload launched from the Earth's surface
is set by the amount of air the payload must displace. At sea level
this is about 1Kg per
sqcm. To have our payload weight as much as the displaced air
(assuming we launch water) it has to be 10m long. If we want an
aspect ration of 30 to 1 this gives a diameter of about 30cm. Giving
us a payload of about 700Kg. This is a huge mass to accelerate at
10,000Gs.

I propose that we build a tunnel through the atmosphere 1meter in
diameter and 50km long at an angle of 45 degrees.

The two issues are keeping the tube straight and holding it in the
air. The first can be done by dynamic feedback. The second can be
done in many ways including baloons (hot air, helium), helicopter
type propellers (electric or fueled), jet engins, etc.

To support the atmospheric pressure at sea level a thickness of 1mm
is more than enough. This gives a weight of 9.5Kg/m (20 tons/Km).
Keep in mind that pressure decreases with altitude

section pressure weight
km relative tons
5 1 20
10 .623 12.5
15 .388 7.8
20 .242 4.8
25 .151 3.0
30 .094 1.9
35 .059 1.2
40 .036 0.7
45 .023 0.5
50 .014 0.3

This gives a total weight of 52.7 tons.

At an altitude of 35Km (at the end of 50Km set at 45 degrees) we have
an atmopheric pressure of only 10g per sqcm. Throughout the tube we
have a pressure of 10g per sqcm (if we keep vacuum pumping out the
bottom end).

So now we can have a payload length of the order of 10cm. So, we can
scale the payload down to the order of 1Kg. This is a much more
reasonable mass to accelarate. Included is a small kick motor to
bring the payload to the exact orbit desired.

I will not go into the details here but very roughly

200 million dollars mass driver
200 million dollars tunnel
200 million dollars operating cost per year

With one launch every 10 seconds for 3 hours per day. This puts over
400,000Kg into orbit per year. At a cost of 700 dollars per Kg (350
dollars per pound).

This is great price for a highly flexible launch service.

The intent is to launch water, metals, silicon, fuel, food, etc.
Things that can survive the acelleration of launch.

Let me know hat you think.

Edwin A. Pell III
ed_pell@...

216 Long Pond Road
Rhinebeck, New York
12572

> Let me know hat you think.

I think that you are on to something, and that you might enjoy
reading _The Bride to Space_, by Mike Combs.

http://members.aol.com/howiecombs/bridge.htm

Xenophile (who wonders if there is anyway to combine this with a
skyhook)

Let me add two points.

The tube will not be exactly straight as the payload
is deflected over 100m in it's 5 second trip through
the tube. Controlling to a slight off straight configuration
is not an issue.

At the beginning we have 9.5Kg/cm for weight per length for
the tube. I add 100% margin and round using 20Kg/cm

Ed Pell

ed_pell@...

>
> The scale of a mass driver payload launched from the Earth's
surface
> is set by the amount of air the payload must displace. At sea level
> this is about 1Kg per
> sqcm. To have our payload weight as much as the displaced air
> (assuming we launch water) it has to be 10m long. If we want an
> aspect ration of 30 to 1 this gives a diameter of about 30cm.
Giving
> us a payload of about 700Kg. This is a huge mass to accelerate at
> 10,000Gs.
>
> I propose that we build a tunnel through the atmosphere 1meter in
> diameter and 50km long at an angle of 45 degrees.
>
> The two issues are keeping the tube straight and holding it in the
> air. The first can be done by dynamic feedback. The second can be
> done in many ways including baloons (hot air, helium), helicopter
> type propellers (electric or fueled), jet engins, etc.
>
> To support the atmospheric pressure at sea level a thickness of 1mm
> is more than enough. This gives a weight of 9.5Kg/m (20 tons/Km).
> Keep in mind that pressure decreases with altitude
>
> section pressure weight
> km relative tons
> 5 1 20
> 10 .623 12.5
> 15 .388 7.8
> 20 .242 4.8
> 25 .151 3.0
> 30 .094 1.9
> 35 .059 1.2
> 40 .036 0.7
> 45 .023 0.5
> 50 .014 0.3
>
> This gives a total weight of 52.7 tons.
>
> At an altitude of 35Km (at the end of 50Km set at 45 degrees) we
have
> an atmopheric pressure of only 10g per sqcm. Throughout the tube we
> have a pressure of 10g per sqcm (if we keep vacuum pumping out the
> bottom end).
>
> So now we can have a payload length of the order of 10cm. So, we
can
> scale the payload down to the order of 1Kg. This is a much more
> reasonable mass to accelarate. Included is a small kick motor to
> bring the payload to the exact orbit desired.
>
> I will not go into the details here but very roughly
>
> 200 million dollars mass driver
> 200 million dollars tunnel
> 200 million dollars operating cost per year
>
> With one launch every 10 seconds for 3 hours per day. This puts
over

>
>> Let me know hat you think.
>
> I think that you are on to something, and that you might enjoy
> reading _The Bride to Space_, by Mike Combs.
>
> http://members.aol.com/howiecombs/bridge.htm
>
> Xenophile (who wonders if there is anyway to combine this with a
> skyhook)

Well, duh!

With a hypersonic skyhook, all the MD has to do is get the payload
(cargo, satellite, passengers) up to about 6500 KmPH and, say, 150 Km
altitude. Then the hook grabs it. Note that the MD *itself* doesn't
have to be 150 KM high, it just needs to get the payload that high,
and the payload needs to still be going about 6500 KmPH. For
instance, if the MD is 50 Km high, then it might need to launch the
payload at 7000 KmPH to be sure that it gets to the right height,
going at the right speed.

Xenophile (who is slapping his forehead again)