Re: Back to the moon? When?
- From: Willie.Mookie@xxxxxxxxx
- Date: Sat, 10 Nov 2007 23:24:25 -0000
On Nov 9, 3:22 pm, "Erich Kohl" <ek...@xxxxxxxxxxxxx> wrote:
Hi everyone,
First and foremost, let me just say that I do believe that the United
States was actually on the moon.
However, I am in a debate with someone who wants to know why it's
taking us (or anyone else for that matter) so long to go back there.
After all, if it was done once before with 1960's technology and
know-how, what's causing the delay in the expedition this time?
My theory is that it must have something to do with politics and
budget, combined with the fact that it might not be as high of a
priority as it once was when the U.S. was in an overt space race with
the Soviet Union.
Any enlightenment that can be offered will help, because I'm not sure
how else to steer my argument.
Work backwards from an astronaut in a mechanical counter-pressure long-
duration spacesuit executing a touch-down with a rocket belt.
http://www.transchool.eustis.army.mil/Museum/Jetbelt.htm
The terminal velocity of a parachuter without a parachute is 54 m/sec
or 195 kph or 125 mph. To reduce this velocity to zero at zero
altitude with a lox-lhy rocket operating at 420 sec Isp, requires a
propellant fraction of 1.3% - So assuming a 100 kg astronaut with
another 120 kg of hardware, that's 2.86 kg of propellant to execute a
perfect touchdown with rocket belt.
100 kg - astronaut
120 kg - hardware (long duration MCP suit, LSS, RB)
3 kg - landing propellant
Prior to that our astronaut entered the Earth's atmosphere and slowed
from 10,850 m/sec to 54 m/sec through aerobraking in their suit, which
is equipped with an ablative TPS layer. This after a 92 hour transit
from the lunar surface. During this time the suit consumes 83 grams
per hour of oxygen, and disposed of 115 grams per hour of CO2 by using
21 grams per hour of hydrogen (Sabatier Process). The suit uses 1 kW
of electrical power - which means it uses another 20 grams of hydrogen
per hour and 160 grams of oxygen. The water made by the fuel cell and
the Sabatier reactor (all MEMs based) is consumed by the astronaut and
also used to evaporatively cool the suit.
Consumed
243 grams per hour - oxygen
41 grams per hour - hydrogen
Produced and disposed of
42 grams per hour - methane (evaporated)
242 grams per hour - water (consumed & evaporated)
Food products Consumed
100 grams per hour - freeze dried food products
Disposed
300 grams per hour - waste products
Total Consumed: 384 grams per hour x 92 hours = 35.328 kg.
36 kg - consumables - return to Earth.
We have a total of 223 kg + 36 kg = 259 kg on the lunar surface before
lift off.
http://en.wikipedia.org/wiki/Lunar_Escape_Systems
A MCP long-duration spacesuit, with integrated TPS and rocket belt
should be capable of lifting off of the lunar surface. I envision a
small rocket belt similar to the bell rocket belt of the 1960s - but
powered by small hydrogen/oxygen high-expansion engines operating at
420 sec Isp. In a sling below the astronaut, between his legs - are
small spheres about 1 meter in diameter that contain oxygen and
hydrogen in a 6:1 ratio the engines need. Each container also has
MEMS based cryogenic control systems, as well as MEMS based rocket
arrays to form independent ACS for each sphere. The spheres have two
ports, one fore and another aft - and they can dock in series of any
length. The LOX/LH can also power the suit systems, and up to 70 kg
of propellant can be stored on the suit itself in 3 spheres each 1/2
meter in diameter.
Lox has a density of; 1,141 kg per cubic meter
Lh has a density of; 70.8 kg per cubic meter
In a mass ratio of 6:1 with 6 kg of oxygen for every kg of hydrogen,
we have for 6 kg 6/1141 + 1/70.8 = 0.019382 cubic meters of volume for
7 kg of propellant in this ratio. Which amounts to 361.1 kg per cubic
meter.
A sphere 1 meter in dimeter has a volume of 0.5236 cubic meters. So,
a sphere would contain 189 kg of propellant. A structural fraction of
3% is possible with such a system, which means the cryogenic vessels,
with MEMs components would have a mass budget of 5.67 kg.
The total mass of each sphere therefore would be 194.67 kg.
Lunar escape velocity is 2,380 m/sec. Our payload at lift off is 259
kg. Our specific impulse is 420 sec. So, our exhaust velocity is 420
x 9.82 = 4,124.4 m/sec
So our propellant fraction is;
u = 1 - 1/EXP(2,380/4,124.4) = 0.43845
And our total mass is 259 kg plus 6 kg for the empty tank, so 265 kg
x 0.43845 = 116.2 kg propellant. Which means 72.8 kg of propellant
can be used prior to departure and still make escape velocity.
Which is enough for flying around the moon with your rocket belt as
well as an extended stay on the moon. 72.8 kg is enough to supply
the astronaut for up to 9 days, or enough to fly around the moon quite
a distance to explore the surface or climb mountains and so forth.
The mass at arrival at the moon would be 259 kg + 195 kg = 454 kg.
The same 43.845% propellant fraction will be needed to land softly on
the moon - so that would be
454 kg x 0.43845 = 199.05 kg
Well, 189 kg of propellant in one tank, and 10 kg from the 73 kg spare
in the other tank, would do the trick. So, another tank is needed.
So to recap - we have an astronaut in a long duration mechanical
counter pressure space suit with an ablative thermal protection system
and rocket belt equipped with 200 kg one meter diameter spherical
propellant pods that can be linked together and drained from the far
end through a two point connection system (think train cars and more
specifically the air braking system of train cars)
Such an astronaut can land and take off from the lunar surface with
two external tanks of the type already described and the total mass is
less than 655 kg on a lunar free return trajectory?
So, ARE THERE ANY ROCKETS THAT CAN PROJECT 655 kg or more into a Lunar
Free Return trajectory?
The answer is yes;
Long March 2C
Long March 2D
Long March 2F
Long March 3A
Long March 3B (send up to 10 at a time!!)
Long March 4B
Soyuz 2
Soyuz U
Proton UR-500 (send up to 10 at a time!!)
Atlas V (send up to 5 at a time!)
Delta III (send up to 5 at a time!)
Ariane IV
Ariane V (send up to 10 at a time!!)
So, these rockets can be hired directly, by interested parties, and
the spacesuit and propellant system I described above could be
developed privately to execute a trip to the moon.
Lets say the spacesuit, advanced life support system, MEMS based
systems, propellant tank and all the rest would cost $200 million to
develop and build 20. Lets say the rockets would cost $200 million to
hire for 20 launches. That's $400 million out of pocket costs. Lets
say the training program and all other costs would cost another $100
million to develop and execute. A total of $500 million. That's $25
million per person. About what a ride to orbit costs today.
So, lets make this a little more commercial.
Imagine that an investment group put up the $500 million and they
offered trips to the moon for the first 20 - for $85 million each.
The 20 would put $85 million in escrow until the flights were
delivered. If they were not delivered in 60 months the escrowed
amounts would be released. The interest and managing of the funds
would go to the owners. So, they'd have use of the money until the
trip took place. The funds would be released to thoe who put up the
$500 million when the trips took place. They would take place most
likely all at once - a group tour - with launches from say Russia and
China simultaneously. The hardware would be developed in Europe and
the US and Japan. There would be 5 group leaders (and one commander
of course) who would also double as reporters and recorders of the
flight for later distribution. Spare rockets would be hired in the US
and from Ariane for overflow if more than 20 riders hire on. A total
of 40 people could fly to the moon in this way.
The Capgemini Merril Lynch World Wealth Report indicates that there
would easily be 200 people who would qualify for an $85 million flight
to the moon.
http://www.capgemini.com/industries/financial/solutions/wealth/worldwealthreport
In short, we could return to the moon with privately hired explorers
within 3 years for less than $1 billion - and zero public money -
using existing rockets.
.
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