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#7658 07/03/06 06:29 PM
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http://www.nasa.gov/home/hqnews/2006/jun/HQ_06270_NASA_Announces_Ares.html

BFR9000 (Big Flying Rocket)
Sure Thing
Apollo Redux
Spreadsheet I and V
NOF (Not Our Fault)


Uncle Al
http://www.mazepath.com/uncleal/
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#7659 07/03/06 09:43 PM
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unfortuantely, they are once again going with throwaway rockets. it would be better to use reuseable, refillable ones. that way we would only have to carry the consumables up


the more man learns, the more he realises, he really does not know anything.
#7660 07/03/06 10:25 PM
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The real cost of getting into space is limited by the rocket equation: delta_v = ve ln(m_i/m_f). After that reliability and safety are the big issues. To get these things a vehicle needs long term development. The old "work horses" are old work horses because they work.

Reusable vehicles will, of course, be required for manned interplanetary exploration. For now, though, the big dumb booster that works fine and lasts a long time is just fine.

#7661 07/04/06 08:51 AM
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why?

have you watched the vid on it.

they have two launch vehicles. the first takes up a lander, the rocket to get to the moon and the fuel for landing, plus all the essentials for three ppl on the moon. the dock in space and the lander takes them to the moon.

try this one on for size.

one part is throw away tanks. after dock, they are used to head towards the moon, then discarded, but only the tanks. the second part is the travel section. it contains the o2 and all for the trip. it returns. the third part is the lander which stays, then the living section which goes to the moon then travels back to earth. then a small earth recovery section that is all that lands back on earth. once the trip is started back, the second set of tanks is discarded.

during the second trip. they send up new tanks for the trip out and back, a new lander and a new Apollo style return vehicle.

there is no need to discard the part the astronauts used on the moon, as it will be the same part that they come back in.

they could even save fuel by sending the lander and the return fuel out by light sail. it would not require a very large sail, as it would be send months before hand. all it would need to do is get into low earth orbit, then the sun will boost it perhaps 10 meters faster every day. it would only take 25 days or less to get fast enough to get just past the point where the moons gravity is higher than earths, and then start slowing it down enough to stay in lunar orbit.

the only expendable things would be the lander, which could later be used for living longer periods on the moon (or larger crews), the reentry capsule, and the fuel and fuel tanks.

basically everything would be an upgraded Apollo type items. the lander would be a much larger luner lander like Apollo, the reentry capsule would be the same save for more crews. the rockets would basically be the same as Apollo, save for bigger, and with dockable tanks. the only thing that would really be different would be the living quarters which would be considerably larger than the ones used for the Apollo, but would be very simular to the ones used in the iss, or perhaps in the shuttle.


the more man learns, the more he realises, he really does not know anything.
#7662 07/04/06 08:33 PM
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Hi dehammer,

There are limitations on the performance of any rocket vehicle. It can be shown rigorously from Newton's laws that a rocket can change its velocity only according to the rocket equation:

delta_v = v_e ln(m_i/m_f)

In this expression delta_v is the change of velocity, v_e is the exhaust velocity of the propellant, m_i is the inital mass of the vehicle and m_f is the final mass of the vehicle. (BTW ln(x) is the natural logarithm of x.)

The difference between m_f and m_i is the fuel that is chemically combined and sent out in the rocket's exhaust, which is called the jet.

The exhaust velocity v_e is dependant on the fuel-oxidizer combination and the thermodynamic characteristics if the rocket engine. It is usually a constant.

Observe that the logarithm function increases slowly. That means that to increase delta_v a little bit, m_i has to increase by a lot.

To put something into orbit around the earth a certain orbital velocity is needed. Also, to break away from the earth a still larger velocity, called escape velocity, is needed. Starting from the earth a spacecraft needs 11.2 km/s to get to the moon. No less will do, Again, this is according to Newtonian physics.

This is where the rocket equation comes in. It is used to check if the rocket, with a given mass ratio m_i/m_f and exhaust v_e, can change its velocity enough (delta_v) to get from here to the moon.

The mass ratio m_i/m_f is the major problem related to the use of ALL rockets.

All the parts, capsules, boosters or whatever come from the earth and are subject to the same mass ratio limitation. If you want to move a kilogram of mass from the surface of the earth to the surface of the moon a cerain mass ratio is required.

The reason that tanks are dropped when they are empty is that you don't have to pay a mass ratio price by hauling them all the way to the destination. Every kilogram costs!

Beside these physical limitations on the use of rockets there are several other issues that are important. Rockets are high energy systems that carry enormous thermal and mechanical loads. To get an idea of this think about the shuttle's weight, about 5 megatons. That's mostly high energy fuel, in accordance with the rocket equation. A shuttle launch is like setting off a 5 megaton bomb in slow motion. That's a lot of stress. To make it reusable a mass ratio penalty has to be paided. To beef up structural members the mass has to increase. (Or invest in materials research.)

This also makes for a more complicated vehicle. This is where reliability comes in. Single use throw-away boosters are far more reliable than the multi-use space shuttle.

Well there is much more to be said, but I don't want to write a treatise on the subject, not here anyway!

I just want to make two points:(1) mission design, planning and implementation is a very complex subject that involves a wide range of considerations and many compromises; (2) no particular method or methods are inherently better than any other, it all depends on what you want to accomplish and what you've got to do it with.

Dr. R.

#7663 07/04/06 11:39 PM
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why reinvent the wheel.

the shuttle engines are used a lot more times that the ones going to the moon ever will. so why should they invent new engines to do the same job.

as far as the tanks goes, i am aware of that. that is why i specified multiple (tanks as in plural) ones that could be discarded in pairs (yes i did not say this) as they were emptied.

part of what you wrote is not near what i was talking about.

one thing you are overlooking is that the fuel to return to the earth has to be carried from the earth to the moon some how. same with the lander and the fuel to land it. if they send them out first using the solar sail (or light sail as you prefer) it would take quite a bit of time, but would not require any fuel. on the other hand, since there is no hurry to get it there (no consumables being used) there is no need to hurry it up. there is conceivable a way of landing supplies on the surface with much less fuel than otherwise would be needed so that it would be there when the astronauts arrived. this would allow them to have a much better mission, with a considerable saving in fuel and money.

If i remember correctly, the Apollo style rockets cost something alone the lines of 200000+ dollars for every pound sent into orbit. it takes hundreds of pounds of fuel to take the lander and fuel to moon from earth orbit and the fuel to return the living quarter back. just think of how much fuel you would be saving for not taking the reentry capsule to the moon. for Apollo, they used the reenty capsule for the trip there and for one person to stay in in orbit. why he was there i dont know. IF the command module is the part they live in and they use it both for the trip to the moon, and the time on the moon and the trip back, there is no part that is left in lunar orbit. no wasted equipment, no wasted fuel carrying it. since it will not be reentering the atmosphere, it would not have to be streamlined like the reentry capsule was. when not used for lunar travel, it could be docked with the space station, allowing more room for them.

multiusing equipment is much better use of funds than single use.


the more man learns, the more he realises, he really does not know anything.
#7664 07/05/06 06:27 PM
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It is not about reinventing the wheel.

When it comes to space exploration false economies like reusable vs. single-use vehicles should be avoided. It is more a matter of efficacy and cost.

Sure you can use the shuttle engines many times and that is bound to save some money. There are, however many costs beside the monetary. How many astronauts lost their lives during shuttle flight ops? That is a heavy cost that must be figured in.

On the monetary side, the last time I looked the cost of putting most payloads into orbit is not cheaper via shuttle. Shuttle launches are subsidized, so there is a false economy here.

Have you noticed that the military is not using the shuttle as much. Maybe they think it is too unreliable for things that involve national security.

Reusable spacecraft are in principle more economic. However, this will require a sustained development effort. The shuttle is the very first and only step in this direction.

In terms of efficacy, it seems that NASA has chosen an approach, using throw-aways, that has been historically more reliable. This way NASA will at least have a program.

The best use of funds is the use that succeeds!

We are no where near the point were we can gas up the space ship and shoot off to Mars. Space technology is NOT a mature technology.

#7665 07/05/06 10:13 PM
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The photon rocket is theoretically the most efficient type of rocket. You get the largest speed for a given final mass/initial mass ratio.

#7666 07/05/06 10:43 PM
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Quote:
Originally posted by dr_rocket:
Reusable spacecraft are in principle more economic. However, this will require a sustained development effort. The shuttle is the very first and only step in this direction.
Is this really true? With a multi-stage rocket, you dump the extra mass as the fuel it contains is used. With a shuttle, you dump the boosters, but you also take a lot of mass up and back.

Payload is not the only measure of value. The large working volume of the shuttle bay is unique. One could imagine using a Saturn V and putting something like this in the 3rd stage. But, then you have to either dump it or get it back down safely.

#7667 07/05/06 10:48 PM
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Quote:
Originally posted by Uncle Al:
http://www.nasa.gov/home/hqnews/2006/jun/HQ_06270_NASA_Announces_Ares.html

BFR9000 (Big Flying Rocket)
Sure Thing
Apollo Redux
Spreadsheet I and V
NOF (Not Our Fault)
You can point to failures so NASA makes an easy target. That is, until you ask yourself, "What project have I taken to completion that is as cool as landing people on the moon or a robot on Mars?"

The successes are pretty damned cool.

You appeared to agree once:
"Let there be no doubt who has the biggest technological balls on Earth"

http://groups.google.com/group/sci.physics/msg/57d4f2b59e145762?dmode=source&hl=en

#7668 07/05/06 10:56 PM
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Actually, if you think about it, you should be able to travel throughout the solar system without using any energy (you could gain energy).

You could use electromagnetic fields (e.g. a rail gun) to accelerate a spacecraft from a space station orbiting Earth to one orbiting Mars. When it arrives at the space station orbiting mars its kinetic energy can be converted back to electrical energy.

No energy is lost and you can actually gain energy from the orbital motion of the planets.

#7669 07/05/06 10:58 PM
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Space Scuttle engines are crap. They weigh much too much because they are reusable rather than use and toss. Their insides fracture and spall off on both the LOX and liquid hydrogen sides. They must are reworked at obscene cost after every flight.

Every time you disassemble and reassemble, you screw up something,

http://images.spaceref.com/news/2003/9.6.2003_05.med.jpg
"EARTH SCIENCE MISSIONS ANOMALY"
http://www.spaceref.com/news/viewsr.html?pid=10299

The major payload of the Space Scuttle is the Space Scuttle. That's stupid. Junk the Space Scuttle and put on a cargo cowling. Redline payload is 22 tonnes (marked down from 25 tonnes for safety diddles). Empty weight of orbiter without engines is 68 tonnes. STUPID. 76% of every launch is wasted. If you need people on a flight, send them back in a disposable capsule. Computers fly the thing either way.


Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz3.pdf
#7670 07/06/06 12:17 AM
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Quote:
Originally posted by Uncle Al:
If you need people on a flight, send them back in a disposable capsule.
Great argument for the space station. I am fairly sure you didn't intend that.

I don't see how you do satellite repair or recovery without the shuttle.

You can argue forever about whether it is the best or most cost effective way to do the job, but it is still pretty damned cool.

#7671 07/06/06 12:20 AM
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Quote:
Originally posted by Uncle Al:

Every time you disassemble and reassemble, you screw up something
Every time?

You are not welcome in my lab! We manage to take things apart all the time without screwing up things.

#7672 07/06/06 12:51 AM
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Quote:
Originally posted by dr_rocket:
Sure you can use the shuttle engines many times and that is bound to save some money. There are, however many costs beside the monetary. How many astronauts lost their lives during shuttle flight ops? That is a heavy cost that must be figured in.
not one was lost due to engine failure. they all died due to complacency. the thing your ignoring is the percentage that have been lost due to single use rockets vs lost due to multi use rockets. its much higher percentage for the single use rockets.

Quote:
On the monetary side, the last time I looked the cost of putting most payloads into orbit is not cheaper via shuttle. Shuttle launches are subsidized, so there is a false economy here.
no, its more expensive, but they are also bigger and more complex. in addition, most of the expense is involved with the throwaway portion of the shuttle.

Quote:
Have you noticed that the military is not using the shuttle as much. Maybe they think it is too unreliable for things that involve national security.
every heard of aurora. its top secret so you will not hear of much about it, but it is known to exist, it is known to be used by the military, and its known to be a multi use manned rocket.

Quote:
Reusable spacecraft are in principle more economic. However, this will require a sustained development effort. The shuttle is the very first and only step in this direction.
the first step is the most expensive. after that its largely a matter of modifying what you have learned to meet the new system requirements. a few new techniques will need to be developed, but nasa is already working on them for other projects.

Quote:
In terms of efficacy, it seems that NASA has chosen an approach, using throw-aways, that has been historically more reliable. This way NASA will at least have a program.

The best use of funds is the use that succeeds!
what they have decided to do is to upgrade the same system that was used before. it failed once out of 7 tries. how is that more successful than the shuttle

Quote:
We are no where near the point were we can gas up the space ship and shoot off to Mars. Space technology is NOT a mature technology.
what does this this have to do with mars mission at this time. nothing. it does give us more work in that direction. but hardly anything else.


the more man learns, the more he realises, he really does not know anything.
#7673 07/06/06 12:59 AM
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Quote:
Originally posted by J. Arthur God:
Is this really true? With a multi-stage rocket, you dump the extra mass as the fuel it contains is used. With a shuttle, you dump the boosters, but you also take a lot of mass up and back.
yes, but they also dump the engines too. that means they have to have engines on each section. when you dump only the fuel tanks you dont have to have more engines, fuel pumps and all of that.


Quote:
Payload is not the only measure of value. The large working volume of the shuttle bay is unique. One could imagine using a Saturn V and putting something like this in the 3rd stage. But, then you have to either dump it or get it back down safely.
or perhaps leave it in space for the next trip. that is the point im trying to point out. why take stuff into space for each trip if it does not have to be replaced.

they shuttle was designed in the 1960's using 1960's technology. the engines was build in the 70's using 70's technology. that means they design is 40 years out of date, and by the time we can build the new rocket, the engines will be 40 years more advanced.


the more man learns, the more he realises, he really does not know anything.
#7674 07/06/06 01:05 AM
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Quote:
Originally posted by Count Iblis II:
Actually, if you think about it, you should be able to travel throughout the solar system without using any energy (you could gain energy).

You could use electromagnetic fields (e.g. a rail gun) to accelerate a spacecraft from a space station orbiting Earth to one orbiting Mars. When it arrives at the space station orbiting mars its kinetic energy can be converted back to electrical energy.

No energy is lost and you can actually gain energy from the orbital motion of the planets.
the rail gun appoach would still require fuel (the opject you shoot down the gun) and power, most likely solar. the thing is that the amount of power would require such large solar cell panels that it would be more effecent to use them as light sails. this would allow them to acclerate the ship without the use of fuel of any kind. granted it would take longer. but the upside is that you could take a much larger crew, have them doing experments while on the trip, and very possible some of them would elect to stay on mars for much longer duration.


the more man learns, the more he realises, he really does not know anything.
#7675 07/06/06 01:12 AM
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Quote:
Originally posted by Uncle Al:
Space Scuttle engines are crap. They weigh much too much because they are reusable rather than use and toss. Their insides fracture and spall off on both the LOX and liquid hydrogen sides. They must are reworked at obscene cost after every flight.
have you ever considered how old they are. they were designed in the 60's and built in the 70s. putting new engines in would change the dynamics of the shuttle and could cause it to be totally destroyed by the new engines, even without an engine failure. new technologies and techniques have long since been developed, but cant be retrofitted to the system.

Quote:
Every time you disassemble and reassemble, you screw up something
as others have pointed out, if something gets screwed up, its the person doing it, not the system.

Quote:
The major payload of the Space Scuttle is the Space Scuttle. That's stupid. Junk the Space Scuttle and put on a cargo cowling. Redline payload is 22 tonnes (marked down from 25 tonnes for safety diddles). Empty weight of orbiter without engines is 68 tonnes. STUPID. 76% of every launch is wasted. If you need people on a flight, send them back in a disposable capsule. Computers fly the thing either way.
that would be called a unmanned rocket and its used quite often already. why should they build a high risk single use rocket every few months to replace the shuttle. AND they do need people up there on a frequent bases. what use is there going to space if man does not go.


the more man learns, the more he realises, he really does not know anything.
#7676 07/06/06 01:13 PM
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Quote:
Originally posted by dehammer:
Quote:
Originally posted by Count Iblis II:
Actually, if you think about it, you should be able to travel throughout the solar system without using any energy (you could gain energy).

You could use electromagnetic fields (e.g. a rail gun) to accelerate a spacecraft from a space station orbiting Earth to one orbiting Mars. When it arrives at the space station orbiting mars its kinetic energy can be converted back to electrical energy.

No energy is lost and you can actually gain energy from the orbital motion of the planets.
the rail gun appoach would still require fuel (the opject you shoot down the gun) and power, most likely solar. the thing is that the amount of power would require such large solar cell panels that it would be more effecent to use them as light sails. this would allow them to acclerate the ship without the use of fuel of any kind. granted it would take longer. but the upside is that you could take a much larger crew, have them doing experments while on the trip, and very possible some of them would elect to stay on mars for much longer duration.
Yes, intitially the system would require some fuel. But once it's running you don't requitre a net input of energy. Because there is no friction in space, you can collect the kinetic energy back when the spacecraft has to slow down. using a coil you can convert the kinetic energy back to electrical energy.

#7677 07/06/06 04:06 PM
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im not sure your talking about a coil gun.

what it does is use a series of electromagnetic pulses to push a payload down a rail using a magnetic responsive bucket of some type. once the payload reaches the sufficent speed, the bucket is slowed down and returned to be loaded again. there is no way to collect the kinetic energy back. at the end when it starts slowing down, it has to fire more loads along the rail in the opposite direction.


the more man learns, the more he realises, he really does not know anything.
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