Look out! Buzz Aldrins got a plan...

Rxke · 2006-02-26 03:31:23

that just does not make sense MarsDog. You'd end up spending 90% of your military budget on stuff that's *unusable* in any given conflict. It would be like building hundreds of aircraftcarriers, perpetually circling around on the seas, from America to the gulf coast and back, another set from America to say china and back etc etc.
If a conflict breaks out, these carriers would just stay doing the same, circling... one in ten, twenty, hundred... would *occasionally* come close enough to the conflictzone to be actually useable. The others just keep circling and circling... Twiddling their thumbs.

Does. Not. Make. Sense.

Austin Stanley · 2006-02-26 04:19:21

But a cycler as a military vehcile is stupid. What good is a military vessle that only approachs it's target once (for a very short time period) every 2 years or so?
Cyclers as military bases, to stage missions from.
Biggest military and security issue is information gathering.
Launching spy probes, projecting a presence to control.
As the saying goes; the threat is greater than the execution.

Your not getting it. You can't stage a mission from a Cycler, because 99% of the time, the Cycler will not be "on station" when you need it. Cycler's spend the vast majority of their time out in interstellar space, and fly-by planets only briefiely, and at high velocities. Of there several year orbits, Cyclers are in the vicinity of their potential targets for a matter of days at best.

And even when the cycler is in the vicinity of they system stageing anything from them is incredibly difficult, because they have all that remendous velocity.

GCNRevenger · 2006-02-26 09:02:54

MarsDog, you keep on uttering words, but they are making progressively less sense... If you can't come up with a reason why this does not make them impractical but you continue to support them anyway, then you are as stupid as they are.

This is a logical fallacy.

No. I am not going to let you change the subject to rhetorical or philosophical jujitsu; its really very simple, if you continue to support the cycler concept without a defensable reason, then are being irrational and letting your emotions rule over facts. And thats just stupid.

"Combine the beam of a large number.
Phase locked, it would act as one giant large diameter source... Power limited in nuclear reactors.
Potential power considerably greater if you beam the power. "

You are just babbling, you have no idea how hard it would be to make such a contraption, and even if you could it wouldn't be useful, since one beam could only accelerate one smallish ship at a time and it would take weeks or months. This is not practical for regular flights anywhere, especially not catching the fast-moving cycler as it passes. Even as a direct flight propulsion, the acceleration is much too slow to beat a GCNR or NSWR engine despite higher efficiency.

"Moving to space is dependent on robots.
Imagine it and have the robots build it.
Cost is the robot. One good robot to build more."

More babeling... futureistic Von Neuman robots aren't going to magically make your giant spinning city-cycler cheap.

"Cycler is a destination. Like a city supported by the countryside."

Whats wrong with building the city in the countryside then? Or at least in orbit around it? No stupid fool would build a city that you can only leave or enter once a year! All the reasources, the atoms for building things, are in the "countryside" so having to import everything to the cycler doesn't make it much of a destination!

You keep on making noises about how gravity wells are such bad things, because they take so much fuel to escape, right? Well guess what, in order to bring things to the cycler, you have to burn quite a bit of fuel to accelerate up to its speed anyway. And I still bet that the reasources the cycler needs will have to be lifted FROM a gravity well anyway. So, how much do you really gain not having to re-push the cycler?

Listen to Mr Stanley, and remember that you have to accelerate and decelerate from the cycler when you leave and arrive at ports of call. This takes exactly the same amount of fuel as it would to get there if you didn't use a cycler at all. Exactly the same amount. The only bennefit to a cycler is having a bigger habitat which to ride during the trip.

The thing of it is, the habitat doesn't comprise that much of the mass of a ship, and the direct flight ship overall does not weigh much more then the little short-range shuttle needed to reach/depart the cycler. Also, because of the cyclers longer travel time, they will cost more to operate per-round-trip and is less efficient per-seat.

As long as you are reusing the direct flight ship, the cycler doesn't save you anything, since the fuel you save is canceld out by the increased operating costs and the advantage of a direct ship being able to transit four times per every trip the cycler can. Thus, the cycler has to be more then four times as big roughly to even break even per-trip then the direct ship. I think I know which one investors will put their money in.

Cyclers have been likend to ocean liners traveling between ports, but do people use ocean liners for travel anymore? No, they do not, air travel - like direct flight - has long since proven to be the superior choice by vote of the customers' dollar. The comparison is clear, a jet liner can make the trip far faster and the same jet can carry just as many people because it is so much faster. A cycler, also like an obsolete ocean liner, is unable to leave just any time, and has to wait for its orbit to carry it around. Cyclers can't be made to go any faster or leave at will either dispite improved propulsion, because they have to follow a free-return orbit or else they will overshoot their next port of call.

One big difference between the ship/plane analogy and cyclers vs direct ships is that the cycler is actually the more dangerous option. The little short range shuttle has to accelerate to free-return speed too, so if it misses the rendezvous with the cycler, it will be going too fast to turn around without a thousand tonnes of rocket fuel. If you can't turn around, you will have to make the whole 18mo+ trip in the little shuttle, where your passengers will all die. Badly... The cycler can't turn around to pick you up if you miss.

These last two paragraphs really do cement the cast against cyclers for mass transit I think, so the issue is clear. You have had the problems with cyclers explained to you several times now MarsDog, but you continue to refuse to address them. These problems are facts, and if you can't show that they aren't really problems or can find a way around them, then it is clear you support cyclers with emotion and sentimentality, not logic or reason, which is the hallmark of a fool.

MarsDog · 2006-02-27 12:09:14

if you continue to support the cycler concept without a defensable reason

Direct to Mars needs manufacturing on Mars,
propellants for a cramped, not well shielded return.

The cycler can provide comfortable 2 way transport,
before manufacturing capabilities are built on Mars.

You are just babbling, you have no idea how hard it would be to make such a contraption, and even if you could it wouldn't be useful, since one beam could only accelerate one smallish ship at a time and it would take weeks or months

5 billion watts from Solar Power Satellite
http://www.freemars.org/history/sps.html

50 lb thrust from experimental electric rocket motor the size of shuebox
http://www.waynesthisandthat.com/ep2.htm

Microwave oven is 77% efficient; add nanotubes for greater efficiency
http://www.nanotechweb.org/articles/news/4/10/7/1

The cycler can't turn around to pick you up if you miss.

But it could beam the shuttle craft power for emergency corrections.

=============================================

Moon cyclers first.
http://www.marsinstitute.info/rd/facult … /in10.html

Then send a few cyclers to Mars.
.

Rxke · 2006-02-27 12:50:58

5 billion watts from Solar Power Satellite

Yeah, from GEO to surface... for a 5 x 10 kilometer SPS... "The SPS would weigh 30,000 to 50,000 metric tons."

You could do quite a couple of DRM III's for that. And develop nulear rockets with the spare change.

GCNRevenger · 2006-02-27 15:14:40

"Direct to Mars needs manufacturing on Mars,
propellants for a cramped, not well shielded return.

The cycler can provide comfortable 2 way transport,
before manufacturing capabilities are built on Mars."

Manufacturing on Mars? We will need that anyway before we can start, start, moving large numbers of people to Mars. And as I and Mr Stanley have reminded you repeatedly, you still have to burn a great deal of fuel to get the shuttles back to the cycler. Where are you going to get that fuel from? Mars of course! It would take a thousand tonnes of fuel at least to deliver one Mars-to-cycler trip worth of fuel from elsewhere. Remember: the cycler does not save you a single gram for shipping cargo, infact its probobly a little worse.

The cycler cannot provide substantially more comfort economically; the size of the cycler required to provide enough volume to support quadruple the crew without going crazy for eighteen instead of two months will be huge. The direct-flight ship can probobly support just as much volume per person and still be much cheaper.

You still aren't listening about the beamed power idea, its really hard to build a giant billion-watt-plus microwave transmitter that can reach tens of thousands of miles. Nobody will ever do anything like that. But even if you could, you would need multiple beams to propell ships on a regular basis, and that will get REALLY expensive. There are some serious technical hurdles with a microwave beam, such as what happens when the Earth eclipses your target vehicle, but more importantly is that its SLOW. Real slow.

...too slow to catch the cycler as it passes, and too slow to return to base before your crew dies on your transfer shuttle. You have got to use either chemical or nuclear thermal engines, those are your only options. If you have to spend days and weeks spiraling out from Earth, the cycler will pass and be long gone. The cycler is moving FAST, but the shuttles are moving SLOW. Even an electric engine pushing some kind of propellant instead of a pure reflective sail wouldn't provide you enough thrust for a fast emergency abort.

Moon cyclers? How stupid... a good example that lots of aerospace engineers and physics buffs get enamored with a particular elegant concept and refuse to address the practical problems. Just like you, MarsDog.

GCNRevenger · 2006-02-27 19:13:14

I ought to add a clarification, that there are two kinds of beamed power propulsion, one with propellant and one without:

-Without, the energy beam bounces off a sail to provide thrust. This is extremely slow and not suited to manned travel anywhere, and definatly could not possibly catch a passing cycler. It could hardly even beat a chemical rocket to Mars or back because it takes so long to accelerate despite being more efficient.

-With, the energy beam is converted to electricity and used to power an electric engine. In short, this isn't a whole lot better, the thrust still needs to be in the tens or hundreds of thousands of pounds of thrust. Without a power collection and conversion system of absurd mass, there is no way you will get enough power to achieve this kind of thrust without sacrificing specific impulse. If you sacrifice impulse, then you still have to bring along a huge amount of propellant to effect an abort or acceleration/deceleration quickly.

And even if either one of them worked, it would still only be able to push one vehicle at a time, which would definatly take hours or days whatever method is used, so you could only push a small number of ships up to cycler speed. The rest of the time, the beam array will not be useful.

MarsDog · 2006-02-28 13:14:48

Without, the energy beam bounces off a sail to provide thrust. This is extremely slow and not suited to manned travel anywhere, and definatly could not possibly catch a passing cycler. It could hardly even beat a chemical rocket to Mars or back because it takes so long to accelerate despite being more efficient.

More efficient to carry some propellant in the Solar System;
But none to the stars.
http://www.planetary.org/interstellar/forward.html

With, the energy beam is converted to electricity and used to power an electric engine. In short, this isn't a whole lot better, the thrust still needs to be in the tens or hundreds of thousands of pounds of thrust. Without a power collection and conversion system of absurd mass, there is no way you will get enough power to achieve this kind of thrust without sacrificing specific impulse

"So then why is the Air Force developing these engines when they can't do anything?

Because the military isn't as short sighted as people like to think. The top brass understand that it sometimes takes decades to develop a useful system. If we don't start now we'll never have them when the power systems are finally available."

Maybe use incoming microwaves directly to the engine, instead of converting to direct current and then using a power supply to power the engine ?

And even if either one of them worked, it would still only be able to push one vehicle at a time, which would definatly take hours or days whatever method is used, so you could only push a small number of ships up to cycler speed. The rest of the time, the beam array will not be useful.

Antenna array is a linear device, therefore you can superimpose without generating spurious responses. (As oposed to nonlinear such as a diode which produces mixing of signals +- combinations of the input)

Good link to explain multi beam array design
See 19.10 Equations on calculating multibeam coefficients
http://www.ece.rutgers.edu/~orfanidi/ewa/
.

RobS · 2006-02-28 14:55:04

The best arrangement probably is to replace the "cycler" with a reusable interplanetary hab that provides comfort for the interplanetary transit phase. One parks the hab at L1 between the Earth and moon where it is 95% of the way outside the Earth's gravity well. The amount of fuel needed to send it to Mars from there isn't much; a small burn can destabilize its orbit so that it flies past the moon, which can send it to fly by the earth, where it fires its engines deep in the Earth's gravity well while flying past close to escape velocity for a delta-v of less than a kilometer per second to go to Mars in six months. This is easy, convenient, and takes very little fuel. Departure time from L1 can change depending on last minute equipment glitches, and there are no plane change issues to be a problem. The vehicle to get crew to the hab can be small.

At Mars, the hab goes into one of two orbits: a solar orbit at the Sun-Mars L1 point, which is about a million kilometers from Mars and can be reached from that world in about a month; or better (I think) in a very highly elliptical orbit around Mars. For example, a 1 sol orbit is something like 400 kilometers periapsis and 30,000 kilometers apoapsis. The delta-v to Martian escape is less than half a kilometer per second; to Earth, about 1.5 km/sec for a six-month flight. A hab in that orbit is quick and easy to reach from the Martian surface, too. An orbital plane change could be done without much fuel penalty and the periapsis could be kept above the surface base, making the hab always available as a launch target and as a communications support platform.

Another advantage of this scheme is that the hab spends most of its time near Earth or near Mars. While near Earth, it could be repaired if an emergency overtakes it. While near Mars, it can serve as an emergency backup if something happens on the surface.

-- RobS

MarsDog · 2006-02-28 19:47:48

.
Nuclear near Earth or Mars is unlikely to be accepted.
Rendezvous points at each planet could optimize use of several propulsion systems.

Nuclear boosters for the long distance, which could be jettisoned before Mars,
and the remaining nuclear boosters to slow it down.
.

GCNRevenger · 2006-02-28 20:00:52

Without, the energy beam bounces off a sail to provide thrust. This is extremely slow and not suited to manned travel anywhere, and definatly could not possibly catch a passing cycler. It could hardly even beat a chemical rocket to Mars or back because it takes so long to accelerate despite being more efficient.
More efficient to carry some propellant in the Solar System;
But none to the stars.
http://www.planetary.org/interstellar/forward.html
With, the energy beam is converted to electricity and used to power an electric engine. In short, this isn't a whole lot better, the thrust still needs to be in the tens or hundreds of thousands of pounds of thrust. Without a power collection and conversion system of absurd mass, there is no way you will get enough power to achieve this kind of thrust without sacrificing specific impulse
"So then why is the Air Force developing these engines when they can't do anything?
Because the military isn't as short sighted as people like to think. The top brass understand that it sometimes takes decades to develop a useful system. If we don't start now we'll never have them when the power systems are finally available."
Maybe use incoming microwaves directly to the engine, instead of converting to direct current and then using a power supply to power the engine ?
And even if either one of them worked, it would still only be able to push one vehicle at a time, which would definatly take hours or days whatever method is used, so you could only push a small number of ships up to cycler speed. The rest of the time, the beam array will not be useful.
Antenna array is a linear device, therefore you can superimpose without generating spurious responses. (As oposed to nonlinear such as a diode which produces mixing of signals +- combinations of the input)
Good link to explain multi beam array design
See 19.10 Equations on calculating multibeam coefficients
http://www.ece.rutgers.edu/~orfanidi/ewa/
.

We aren't talking interstellar travel, the trouble is the transit shuttle has to be able to accelerate quickly from orbit to the cycler as it passes, which means that no low-acceleration propulsion will work. Especially nothing sail-based.

The military is looking for low-to-intermediate thrust high specific impulse engines, which I assume to be for spy satelites, LEO-to-GEO tugs, and so on. The USAF came quite close to building a nuclear rocket driven tug back in the "Shuttle will solve all our problems" days.

Again, you have to accelerate quickly to be able to catch the cycler as it passes, and that means for a largeish shuttle you are going to need decent thrust. Something on the order of the RL-10 or RL-60, if not the J-2 or the SSME. There is just no way you are going to get an electric engine with that kind of thrust that doesn't weigh as much as chemical fuel, at least not without sacrificing impulse.

Regular thermal rocket engines achieve power levels in the billions of watts, and even the little tiny RL-10 consumes ~90MW. Your own link showed that power conversion systems and cooling weigh on the order of 1.5kg/kWe, and I bet a light-weight collector for the microwave beam will run you that much again, so you are looking at 300 metric tonnes just for the power system, assuming a superhigh ~90% efficiency. That doesn't include the engine nor the propellant for it, and thats just to match thrust and specific impulse with chemical engines using beamed power.

For specific impulse (fuel efficiency) substantially greater then chemicals engines, you will need even more power, about ten times as much (~1,000MW) to achieve really superior efficiency (power demand increases exponentially with impulse), so you are talking about 10,000+ tonnes for the power, propulsion, and propellant for your ship... Which would make a cycler-sized ship direct flight ship and fuel to power it with or a chemical engine big enough for direct abort.

There isn't a really good way to make a thermal microwave engine either, since the engine housing will have to absorb microwaves, heat up, and pass that heat to a propellant. The trouble is, this microwave absorber will be a solid, and no solid can survive temperatures much higher then 3000K. Because of this, your specific impulse is very limited (specific impulse of thermal engines is limited by temperature), to only about double that of regular chemical engines. I don't think we have a microwave absorber that would do the trick either.

A big phased array antenna can make as many beams as you like, but you have to have power to run all of them still. Since much of the power you generate will never reach the shuttle, you are talking about needing 10-100 gigawatts per shuttle. You just aren't going to have many of these, so there is no way in heck you are going to accelerate/decelerate multiple shuttles to/from a cycler that way. Plus, it will sit unused most of the time I bet... A 100 gigawatt beam would require as much power as a dozens of nuclear power plants combined. Just to push one dinky shuttle?

GCNRevenger · 2006-02-28 20:24:10

The best arrangement probably is to replace the "cycler" with a reusable interplanetary hab that provides comfort for the interplanetary transit phase. One parks the hab at L1 between the Earth and moon where it is 95% of the way outside the Earth's gravity well. The amount of fuel needed to send it to Mars from there isn't much; a small burn can destabilize its orbit so that it flies past the moon, which can send it to fly by the earth, where it fires its engines deep in the Earth's gravity well while flying past close to escape velocity for a delta-v of less than a kilometer per second to go to Mars in six months. This is easy, convenient, and takes very little fuel. Departure time from L1 can change depending on last minute equipment glitches, and there are no plane change issues to be a problem. The vehicle to get crew to the hab can be small.
At Mars, the hab goes into one of two orbits: a solar orbit at the Sun-Mars L1 point, which is about a million kilometers from Mars and can be reached from that world in about a month; or better (I think) in a very highly elliptical orbit around Mars. For example, a 1 sol orbit is something like 400 kilometers periapsis and 30,000 kilometers apoapsis. The delta-v to Martian escape is less than half a kilometer per second; to Earth, about 1.5 km/sec for a six-month flight. A hab in that orbit is quick and easy to reach from the Martian surface, too. An orbital plane change could be done without much fuel penalty and the periapsis could be kept above the surface base, making the hab always available as a launch target and as a communications support platform.
Another advantage of this scheme is that the hab spends most of its time near Earth or near Mars. While near Earth, it could be repaired if an emergency overtakes it. While near Mars, it can serve as an emergency backup if something happens on the surface.

I think the term "cycler" here isn't really appropriate, more like "reuseable interplanetary transfer vehicle"

We might eventually wind up doing something vaugely like this, the trouble is getting BACK to L1 from Mars will require quite a bit of fuel, wouldn't it? Perhaps aerobraking and parking into LEO or an intermediate orbit would be better.

It is a risk to return a ship with a solid-core nuclear engine to Earth orbit since they will still be "hot" for several years after firing, particularly with aerobraking. A GCNR type ship would not have this problem, since the Uranium fuel could be flushed from the engine after firing into space. Solid-core nuclear engines can be dumped into interplanetary space, but these will add up I bet, while a GCNR engine only dumps Uranium vapor.

Note that a solid-core engine is only marginally better then the best chemical engines, so some kind of aerobrake maneuver would be very preferable, and returning to a high Earth orbit would require more fuel and be a lesser though still nontrivial risk.

MarsDog · 2006-03-01 04:12:06

There isn't a really good way to make a thermal microwave engine either, since the engine housing will have to absorb microwaves, heat up, and pass that heat to a propellant. The trouble is, this microwave absorber will be a solid, and no solid can survive temperatures much higher then 3000K. Because of this, your specific impulse is very limited (specific impulse of thermal engines is limited by temperature), to only about double that of regular chemical engines. I don't think we have a microwave absorber that would do the trick either.

In the research stage, expected similar performance to nuclear.
See PDF links at bottom of page.
http://www.islandone.org/LEOBiblio/SPBI115.HTM
http://monolith.caltech.edu/Papers/ParkinThruster.pdf
http://monolith.caltech.edu/Papers/ParkinLauncher.pdf

And if more is needed:
http://scientium.com/diagon_alley/comme … /orion.gif
Release hydrogen onto the reaction plate and zap it with a beam of ??
Maybe stick an iron rod, to be vaporized, in the center of the push plate,
Depositing, to compensate for the ablation.
.

GCNRevenger · 2006-03-01 07:15:10

You aren't listening MarsDog,

If you need 1000-2000MT of rocket fuel for an engine with a ~450sec Isp, then you are still going to need hundreds of tonnes of fuel for an engine with ~1000sec Isp, especially hard-to-store Hydrogen. The NASA DRM-III Earth to Mars nuclear booster is only somewhat smaller then an equivilent chemical booster.

No thermal engine built out of a solid material can substantially exceed this specific impulse reguardless where it gets its energy from, because there are no practical materials that can withstand temperatures much above 3000K. If you can't go higher then this, and by "higher" I mean like 10,000K or above, then your engine simply won't be efficient enough to avoid a huge fuel load. The VASIMR engine requires temperatures up to 1,000,000K to get an Isp of 10,000sec.

A thermal ablation engine isn't a way around the problem either, because the stuff burns off at temperatures similar to what most solids melt/burn at, so it burns off before it can get any hotter, so it is likewise of limited efficiency. It would be impossible to arrange anyway, since the engine would have to face away from the beam for an emergency abort.

A microwave orion? No way, the gas would never absorb energy quickly enough. Orion is only really suitable for nuclear reactions, which are very "dense" by comparison to a diffuse puff of gas. Besides, the shock absorbers and pusher plate would be quite heavy.

You also aren't listening about the kinds of power levels needed for the microwave beam: it does not matter one little bit what kind of engine you have. Electrical, thermal, whatever: they all require the same amount of power to produce the same amount of thrust with a particular specific impulse. Its a simple matter of Newtonian physics, to get a certain amount of push it takes a certain amount of power, and there is no way cheat and get by with less. An engine is a converter, all it does is change one form of energy (heat, electricity, etc) into kinetic motion energy, it can't "make" more energy then is put into it.

Edit: Oh, and thermal ablation engines usually contain lots of stuff that isn't Hydrogen; you need the propellant to be mostly Hydrogen atoms to attain really high specific impulse. If you "burn" an iron bar, despite reaching superhigh 10,000K+ temperatures, the specific impulse still won't be alot better then plain old chemical rockets.

MarsDog · 2006-03-01 22:40:08

If you need 1000-2000MT of rocket fuel for an engine with a ~450sec Isp

http://monolith.caltech.edu/Papers/ParkinLauncher.pdf
Per figure 4. the Isp is between 700 and 800.
The authors claim 10% payload to Low Earth Orbit (Δv=9.6 km/s)
That would need 2 stage taxi to catch the cycler.

thermal ablation engines usually contain lots of stuff that isn't Hydrogen; you need the propellant to be mostly Hydrogen atoms to attain really high specific impulse

Exploring the idea of heating hydrogen to form a conductive plasma, to absorb the microwaves. Perhaps an initial arc, as in a fluorescent tube, with a little mercury.

Electrical, thermal, whatever: they all require the same amount of power to produce the same amount of thrust with a particular specific impulse. Its a simple matter of Newtonian physics, to get a certain amount of push it takes a certain amount of power, and there is no way cheat and get by with less

Momentum is conserved, hence the rocket equations.
Power can go into heat, radiation, etc. (Elastic/inelastic collision)

GCNRevenger · 2006-03-02 09:07:06

700-800sec is hardly any better then conventional chemical engines, and won't shave much mass of the fast abort or cycler rendezvous fuel bill at all, particularly with the engine and tank mass penalties. 10% mass to orbit? Hey, thats no better then the best chemical engines with advanced fuel tank materials and regenerative nozzles.

Multi-stage shuttle? Oh, so now you are throwing away spent rocket stages? You'll have to, since the fuel required to return those stages for reuse will be quite large you know. And what about the fuel for the emergency abort? Staging isn't going to make this problem go away, you will still need hundreds of tonnes of fuel. You still have to bring enough fuel to turn around if something goes wrong, and you have to push that fuel to the cycler every time you rendezvous, which in turn takes VERY large amounts of fuel. Its a vicious cycle.

Basically you are wanting a VASIMR engine with an external rather than internal microwave source? A VASIMR engine still requires a great deal of electrical power to operate its magnetic confinement bottle, nessesitating the high mass collector/converter/cooler apparatus. How much is that going to weigh versus chemical fuel with Hydrogen propellant? Oh, and this magnetic bottle must also be transparent to microwaves and I don't know of any electromagnet material that is transparent to microwaves.

But I digress, this won't work because the Hydrogen can't absorb but a small fraction of the microwave beam because the gas isn't thick enough, VASIMR works because it can reflect the microwaves back and forth inside its bottle, but you can't do that with an external beam.

But even if you could get it to work, VASIMR doesn't have the kind of thrust you need anyway. It takes a full 30 days on the "high thrust" setting to escape Earth orbit with continuous power, so the engine would have to be ten times as big and powerful and require ten times the energy to get one or two shuttles to catch one cycler in the few days before life support runs out.

The beam will also still have to be in the gigawatt range: to put it in presepctive, the average large Earth-based nuclear power plant produces a little under one gigawatt of power. Thats ALOT of infrastructure to push a dinky little shuttle once a year to a cycler.

Even if it did work, even if it did, nobody would be stupid enough to do this; it would be so much better to use the system to push vehicles directly to their destination because you could take advantage of the efficiency offerd by VASIMR and achieve high transit speeds and the ability to depart at almost any time. Remember, a cycler can not go any faster, because if it did, it would overshoot and not loop back around at all.

publiusr · 2006-03-08 14:53:31

If you already have high-efficiency nuclear rockets, then you want the painfully slow and agonizingly rigid scheduling of a cycler even less! Why, why would you possibly want to tie yourself to inflexible, rigid departure times that takes 9+ months to transit just to or from Mars, all that time, utterly wasted, when you could make a quick sixty-odd-day hop with a GCNR/NSWR ship almost any time you wanted?
.

I'm talking farther down the road. If something should happen upon a fast return Mars ship 50 years out, a cycler on the way back might be a good target to dock with for repairs if need be. The more things you have in transit the better.

Austin Stanley · 2006-03-08 23:16:48

I'm talking farther down the road. If something should happen upon a fast return Mars ship 50 years out, a cycler on the way back might be a good target to dock with for repairs if need be. The more things you have in transit the better.

I don't think such a situation is likely. For one, a cyclers are likely to be in a signifigantly diffrent orbit than any direct transfer vehicle, regardless of their velocity. The free return orbits they use are generaly diffrent than the one direct aproach vehicles have to fall back on because they are planning on free-returning both ways.

A fast transfer vehicle is likely to use a dramaticly diffrent orbit than a cycler. And even if they were, by chance, in the same region of space, the diffrence in their velocities would likely be immense. Slowing down to dock with the cycler would be a difficult manuver and would take a large amount of energy, it would probably make more sense to just tough it out to the destination. But such a close encounter bettwen such vehicles would be highly unlikely.

Rember also that cycler orbits are generaly periodic. You can't launch into an effeciant cycler orbit just anytime you want, they are only avaliable at certian time periods, so your cyclers (all of them) are all bound to be at their diffrent destinations at specific points in time, not strung out through space arriving and departing every month or so.

MarsDog · 2006-03-09 14:45:31

Earth Moon transfers; LEO, Lagrange L1 and low Moon orbit will be developed first.
Just like the Moon landing, it won't be Moon direct

To Mars:
http://www.stk.com/pdf/white_papers/070 … vities.pdf

Cyclers will be useful between different staging and transfer points.
A large solar array equipped cycler could boost shuttle craft via microwaves.

Mars_B4_Moon · 2007-04-12 21:08:56

"The Moon doesn't invite to stay"

Apollo 11 pilot Buzz Aldrin
http://www.heise.de/tp/r4/artikel/25/25014/1.html

Mars_B4_Moon · 2007-04-18 10:07:16

Buzz Aldrin planning a space contest

http://www.msnbc.msn.com/id/18163075/

Moonwalker Buzz Aldrin announced plans on Tuesday for a prize contest that would send the winner into space in a bid to spread the dream of extraterrestrial travel beyond the super-wealthy.

GCNRevenger · 2007-04-18 10:40:59

I'm talking farther down the road. If something should happen upon a fast return Mars ship 50 years out, a cycler on the way back might be a good target to dock with for repairs if need be. The more things you have in transit the better.
I don't think such a situation is likely. For one, a cyclers are likely to be in a signifigantly diffrent orbit than any direct transfer vehicle, regardless of their velocity. The free return orbits they use are generaly diffrent than the one direct aproach vehicles have to fall back on because they are planning on free-returning both ways.
A fast transfer vehicle is likely to use a dramaticly diffrent orbit than a cycler. And even if they were, by chance, in the same region of space, the diffrence in their velocities would likely be immense. Slowing down to dock with the cycler would be a difficult manuver and would take a large amount of energy, it would probably make more sense to just tough it out to the destination. But such a close encounter bettwen such vehicles would be highly unlikely.
Rember also that cycler orbits are generaly periodic. You can't launch into an effeciant cycler orbit just anytime you want, they are only avaliable at certian time periods, so your cyclers (all of them) are all bound to be at their diffrent destinations at specific points in time, not strung out through space arriving and departing every month or so.

I agree with this, and even if the cycler had a big microwave beam, there is the simple problem that the difference in velocities is so high that the short time and rapidly changing focal point would make accelerating a shuttle impractical. Remember, you would need an awful lot of G's to change several kilometers per second over the short time (minutes? seconds?) that the shuttle would be near the cycler, too many G's.

A cycler makes no sense in the context of having any kind of high-energy propulsion, it would be better just to launch to LEO and push to Mars with the microwave beam directly if you could mount something like it on a cycler. Cyclers only make sense if you are stuck with chemical rockets or low-energy ion/plasma/solar thermal engines.

Yang Liwei Rocket · 2007-05-26 05:06:56

Former NASA Astronaut Joins Coalition For Space Exploration

http://www.aero-news.net/index.cfm?Cont … da7de39824
Roger Crouch Has Logged Over 471 Hours In Orbit
When you're seeking to advance space exploration, it helps to have someone who knows the territory on your side. The Coalition for Space Exploration told Aero-News Monday it has named former NASA astronaut Roger Crouch to its board of advisors.
The Coalition is a national collaboration of space industry businesses and advocacy groups whose mission is to educate and inform the public on the value and benefits of space exploration. As a board member, Crouch will provide insight and recommendations regarding the organization’s public outreach efforts designed to showcase the importance of America's investment in a robust space exploration program.

Fledi · 2007-05-26 07:33:39

I agree with this, and even if the cycler had a big microwave beam, there is the simple problem that the difference in velocities is so high that the short time and rapidly changing focal point would make accelerating a shuttle impractical. Remember, you would need an awful lot of G's to change several kilometers per second over the short time (minutes? seconds?) that the shuttle would be near the cycler, too many G's.

What kind of shuttle are you talking about, one that would slow down and return to Earth after delivering the passengers?
In this case I agree, but if you make a two way capsule that goes on to the destination (Mars for example) lands there and waits for the next cycler to arrive, then rides along that one back to Earth, I guess it should have enough time to dock between the planets, same way capsules do the docking game in LEO, only on a heliocentric scale.
But I agree with you cyclers are very impractical for a lot of reasons. No minimum energy trajectory to make it periodic, no easy way to maintain it and by the time we need them we will have advanced nuclear propulsion/plasma engines or for the cheaper alternative one way modular spaceships that can serve as a space station in Mars orbit or even be ferried down to the surface in parts.

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#51 2006-02-26 03:31:23

Re: Look out! Buzz Aldrins got a plan...

#52 2006-02-26 04:19:21

Re: Look out! Buzz Aldrins got a plan...

#53 2006-02-26 09:02:54

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#54 2006-02-27 12:09:14

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#58 2006-02-28 13:14:48

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#59 2006-02-28 14:55:04

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#60 2006-02-28 19:47:48

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#62 2006-02-28 20:24:10

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#70 2007-04-12 21:08:56

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#71 2007-04-18 10:07:16

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#72 2007-04-18 10:40:59

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#73 2007-05-26 05:06:56

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#74 2007-05-26 07:33:39

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