New here, asteroids prefered

NERVA has an ISP of 850- from a reaction one million times more powerful than chemical fuel. Like using a napalm airstrike to light a cigarette. The problem with any nuclear rocket is containment- it is hard enough to keep a chemical rocket from melting. Stan Ulam correctly deduced that a fast fission device- a bomb- would be the most effective propulsion system for spacecraft. That was in 1945 shortly after the first one was lit off. It is still the only system that does not waste almost the entire amount of energy being produced. ISP for a Nuclear Pulse Propulsion system would be in the thousands and most probably in the tens of thousands.

--- On Fri, 6/18/10, Victor Smith wrote:

From: Victor Smith
Subject: Re: [spacesettlers] Re: New here, asteroids prefered
To: spacesettlers@yahoogroups.com
Date: Friday, June 18, 2010, 9:53 PM

1. NOT aerobraking- you're right...no atmosphere on the moon- instead, the reverse of a gravity slingshot, utilizing a swing by the moon (or Venus, the sun or both plus Luna for far out or very fast rocks) to reduce or augment delta v so as to modify an asteroids orbit so that it makes rendezvous with either a L-point or a position in Earth orbit at a nice safe speed to be met and towed to processing facilities. BTW, lunar orbit would suffice for processing facilities as well. I don't know that I would promote aerobraking anything past meteoric size in the Earths atmosphere due to safety considerations...luckily, though, it's not necessary.

2. Nuclear Pulse is NOT the only viable nuke propulsion system:

Begun in 1955, by the USAF, and then taken over in 1958 by NASA at that agencys' creation, NERVA (Nuclear Engine for Rocket Vehicle Application) was the expected rocket motor under development for the planned manned Mars mission then scheduled for launch in November 1981 with a manned landing in August 1982. In the late 1960s and early 1970s the Nixon administration drastically cut funding for NASA and NERVA. Eventually the NERVA/Rover program lost its altogether, and was terminated on January 5, 1973. Between 1959 and 1972, the Space Nuclear Propulsion Office oversaw 23 reactor tests at the Nuclear Rocket Development Station at the AEC's Nevada test site in Jackass Flats. These included the KIWI, PHOEBUS, PEEWEE-1 AND NUCLEAR FURNACE 1 test series on the rover reactor systems and the NRX-A2, A3, EST, A5, A6 and XE-PRIME series on the NERVA engine.

The NERVA program started out with the following objectives:

multi-mission capability

man-rated

based on full-flow topping

minimum chamber temperature of 2360 K and a minimum chamber pressure of 450 psia

minimum 75,000 lbf thrust

endurance of 600 minutes and up to 60 cycles

capable of 85,000 lbf and 500 psia transients

incorporating adequate shielding for manned operations

storable for 5 years on the ground, 6 months on pad, and 3 years in space

transportable by land, sea, and air

To meet these objectives, NERVA consisted of two reactor projects: the Nuclear Reactor eXperiment (NRX) and the eXperimental flight Engine Prototype (XE-Prime).

During its lifetime the NERVA/Rover programs accomplished the following records:

highest power: 4500 megawatts thermal power

5,500F exhaust temperature

250,000 pounds thrust

850 sec. of specific impulse

90 min. of burn time

thrust to weight ratios of 3 to 4

By the time the NERVA program was terminated, the NERVA-2 had been designed that would have met all of the program's objectives. Two of these engines would have been fitted to a NERVA stage capable of powering a manned interplanetary spacecraft. The final NERVA Alpha Flight Engine reference configuration, as documented at the end of its development, was an engine that could be launched together with its stage and a payload in a single shuttle launch. The final engine planned for the Mars mission would have been a scaled up version of this design and the Mars ship would have incorporated a pair of them.

http://www.astronautix.com/engines/nerva.htm

http://www.daviddarling.info/encyclopedia/N/NERVA.html

http://en.wikipedia.org/wiki/NERVA

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19910017902_1991017902.pdf

http://www.scribd.com/doc/29472345/How-the-NERVA-Rocket-Engine-Works

From: Gary Church

Sent: Friday, June 18, 2010 8:01 PM

To: spacesettlers@yahoogroups.com

Subject: Re: [spacesettlers] Re: New here, asteroids prefered

I am pretty much all about dealing with radiation first of all, then propulsion. NASA is making some plastic hull material that mitigates GCR. I think this is pretty important stuff. If you have an out plastic hull and an inner and fill the void up with moon water then for the first time there may be a way to actually go out there and not die of cancer. Of course to push all those hundreds of tons of water (minimum) you will need nuclear propulsion and the only viable nuclear propulsion system is Nuclear Pulse Propulsion (bombs).

--- On Fri, 6/18/10, brooksn wrote:

From: brooksn

Subject: [spacesettlers] Re: New here, asteroids prefered

To: spacesettlers@yahoogroups.com

Date: Friday, June 18, 2010, 9:23 AM

There will be countless candidates of meteroids/asteroids 5 - 10 meters across that come very close to Earth now. Adjusting their trajectories with the mass of a small spacecraft by meeting and 'parking' over and in the direction you want the object to go should take very little energy.

p = MV = Ft

p momentum

M mass

V velocity

F force

t time

Since we are picking from a very small class of asteroid, 10 meter, 2900 tons, we have kept M very low. Since we pick the asteroid with a favorable orbital path (just hitting or just missing Earth) we can keep the V very low. Since we are picking the asteroid we can also have more t time on our hands to adjust its orbit. Without doing the math it would seem to be a very cheap option, energetically, to grab an asteroid of our choice and put it into an aerobraking trajectory. And then bring it to ISS and begin study and processing of its material.

I can't see how the same mass leaving the moon to ISS would be lower in energy costs, delta v, then minor adjustments to the same mass already on course for Earth.

Brooks

--- In spacesettlers@yahoogroups.com, sraj wrote: