Look out! Buzz Aldrins got a plan...

Commodore · 2005-11-12 20:40:56

If you got the December 05 issue of Popular Mechanics, then you already know the details.

It features a cycler in permenent solar orbit of the most absurd shape you'll ever see. Picture a 2 step ladder spinning in space. It even has pressurized elevators to transport crew between the hab and the docks and reactor. It supports a crew of 8 for 5 months.

The oddest part has to be the Semi-Cycler. This thing makes regular trips as well, but its sole purpose seems to be to ferry crews between the cycler on the Mars end of its orbit, and Mars orbit. On the Earth end, the CEV is launched directly from earth to somewhere between the Earth and the Moon (I'm pretty sure they mean L1), were it refuels on lunar fuel. It then uses that fuel to meet the cycler. Why he needs something that goes all the way from the Earth to Mars to ferry people from Near Mars Space to Mars Orbit is beyond me.

Finally, the first mission lands on Phobos first to set up a base using by then tried and true lunar hardware to be used as a launch pad for the following missions to the surface. Phobos might have useful minerals, but unless it has fuel I see no reason to add it to the list of gravity wells we need to deal with that early on.

Overall I think he's on the right track, he just trips on every tie. He mentions setting up infrastructure, and making the Mars program politics-proof. Heres how he should have done it.

The cycler is a good idea, but its much too small. It needs to be able to support a much larger crew with the supporting greenhouses, labs, crew quarters, ect. A little closed loop ecosystem away from home. And I would perfer one shaped like a revoler, and not a ladder.

I don't know what he was smoking when he dreamed up the semi-cycler. If you need to shuttle people from the cycler to orbit, at either planet, have one at each planet. It can be much smaller and cheaper. It would also solve the most dangerous weakness I see in the mission, a failure to dock in Near Earth Space. A CEV drained of fuel and crammed with a crew it can't support is the worst thing that happen to a program. We are better off having a shuttle in LEO, or maybe lunar orbit. Some thing that can chase the cycler down if need be, and return under its own power. Same thing on the Mars side. Theres plenty of fuel on Mars. If we can expolit it on the moon we can on Mars.

Theres plenty of good reason to have an outpost in Mars orbit. But Phobos isn't the place to put it. If it were up to me I'd build an exact copy of the cycler and park it in Mars orbit. The perfect place to store landers, and fuel for your Shuttle. Plus you can grow and stockpile food on it. Its also a retreat in the event things go pear shaped on the surface.

I'll scan the article as soon as I get to my scanner.

Austin Stanley · 2005-11-12 22:37:20

We've talked about cyclers quite a few times, and my feelings about them haven't changed much. In the short term at least I don't see them as worth the expense.

You see when a cycler approaches Mars or Earth it is still moving at essentialy the necessary velocity to fly back to Mars or Earth. It can't stop, it going to fast, and breaking it into orbit would defeat the point of a cycler. So you have to catch it. To do this you have to rendevou at essentialy the same speed the cycler is going, which means you have to spend nearly as much energy as if you were going to send your payload to Mars/Earth anyways.

This creates to problems. First such a high speed rendevous is very difficult to plan and carry out, your time frame is relativily short and you only have one chance at it. Secoundly, if you miss the rendevous you have essentialy no abort option. Your rendevou craft is traveling fast enough to send it away from your planet for a very long time.

So the advanatage of a cycler is very limited. Essentialy you get two things. The ability to operate a larger craft with a higher Life Support efficancy, saving on your consumables for the voyage, and some small propulsive savings and the ability to use a small cheap redevous craft to meet the cycler instead of the large vessle that you would need to make the voyage on your own.

However currently the savings you would get in life support effeciancy and delta-V are very small for near term missions. The diffrence in 90% vrs 99% closed life support for 6 people or so is not that great. And if you want an abort option for the redevous craft it either has carry enough propelent to slow down to a reasonable return time, or enough life support to support the crew untill the come back around naturaly, it might need some way to re-enter/aerobrake as well. This eliminates any advantage the redevou craft might have in the first place.

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To me the solution to reducing the cost of the voyage to Mars in back is to improve the engines and to develop reusable transfer vehicles. Cyclers just don't make any sense to me. Especialy not currently, maybe someday if/when we are sending 100s of people an opposition to Mars they might be logical, but even then I have my doubts. The more people you send the more important an abort option becomes and that just destroys your advantage.

Palomar · 2005-11-13 11:46:28

The oddest part has to be the Semi-Cycler...
I don't know what he was smoking when he dreamed up the semi-cycler.

Commodore · 2005-11-13 20:16:11

@ Austin Stanley: Yeah, the deal breaker really is the shuttle. You need something with a lot of power to keep pace, and as a last resort, return to earth in short order. Nuclear Thermal perhaps?

Redevou shouldn't be all that hard though. We match orbit with things all the time. The biggest issue would we a malfuntioning docking bay. Now if we have to dock with a spinning ladder, thats another story.

Commodore · 2005-11-13 20:17:59

The oddest part has to be the Semi-Cycler...
I don't know what he was smoking when he dreamed up the semi-cycler.

I know, he's probably going to punch me now.

Austin Stanley · 2005-11-13 23:16:49

@ Austin Stanley: Yeah, the deal breaker really is the shuttle. You need something with a lot of power to keep pace, and as a last resort, return to earth in short order. Nuclear Thermal perhaps?
Redevou shouldn't be all that hard though. We match orbit with things all the time. The biggest issue would we a malfuntioning docking bay. Now if we have to dock with a spinning ladder, thats another story.

You hit my point exactly. The cycler is fine (if a bit expensive) it's the shuttle that makes the thing difficult. It has to be cheap, very powerful, and light. But of course as the adage goes you can only have two of those. It has an exceedingly difficult job, it has to be able to match speed with the fast moving cycler very quickly (before it's limited life support runs out), so it must be very powerful. The redevou demands some sort of high thrust engine, either chemical or as you say some nuclear thermal option. Unfortuantly chemical's low thrust means it can't be light (though it might be cheapish) and nuclear option means it probably can't be cheap (though it might be lighter).

But after further consideration, I don't think a powered abort is realy possible either way. To do a powered abort it has to carry a signifigant fraction of the TEI/TMI delta-V with it. Even with a NTR this is still going to be A LOT of propelent, and it increases the mass which increases the amount of propelent necessary to catch the cycler in the first place. Without some sort of VERY high ISP high thrust engine such as GCNR/NSWR/Orion I just don't think it is going to be possible. However, none of these engines are going to be cheap either. Without some other magical way to stop in space (and I am open to suggestions) the crew is going to be in it for the long hall. And if you have to provide for that, you might as well go on and forget the cycler and send them in the shuttle in the first place.

-------

As for the difficulty of rendevou I don't think it's impossible to pull of, but it will be considerably more difficult than any we have done before. The craft are going to be docking at a MUCH higher delta-v than we have ever done before. While their relative delta-V's may no be that diffrent (on the other hand to save some propelent they might well be) the high delta-V makes errors in positioning much more critical. An error is twice as big when you go twice as fast.

More critical however is the short and critical time frame to pull it off. Unlike previous docking missions both craft are on a hyberbolic (or nearly hyberbolic) orbits, possibly diffrent ones which only intersect for a limited period of time. Unlike the most previous rendevous missions there isn't an (realitivly) unlimited number of tries you can take before you do it. There is a time window that must be delt with, either you meet it, or you fly into empty space, no fun.

But like you said rendevous is not the only reason you need some sort of abort option. Any malfunction that prevents the docking will cause disaster.

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To me they cyler approach seems most like shooting someone out of a cannon to catch a ride on an airplane. Not a very smart thing to do.

Commodore · 2005-11-14 14:10:27

You hit my point exactly. The cycler is fine (if a bit expensive) it's the shuttle that makes the thing difficult. It has to be cheap, very powerful, and light. But of course as the adage goes you can only have two of those. It has an exceedingly difficult job, it has to be able to match speed with the fast moving cycler very quickly (before it's limited life support runs out), so it must be very powerful. The redevou demands some sort of high thrust engine, either chemical or as you say some nuclear thermal option. Unfortuantly chemical's low thrust means it can't be light (though it might be cheapish) and nuclear option means it probably can't be cheap (though it might be lighter).
But after further consideration, I don't think a powered abort is realy possible either way. To do a powered abort it has to carry a signifigant fraction of the TEI/TMI delta-V with it. Even with a NTR this is still going to be A LOT of propelent, and it increases the mass which increases the amount of propelent necessary to catch the cycler in the first place. Without some sort of VERY high ISP high thrust engine such as GCNR/NSWR/Orion I just don't think it is going to be possible. However, none of these engines are going to be cheap either. Without some other magical way to stop in space (and I am open to suggestions) the crew is going to be in it for the long hall. And if you have to provide for that, you might as well go on and forget the cycler and send them in the shuttle in the first place.

Buzz seemed to think that the CEV launch, L1 refueling, and rendevou could be done in 10 days. That assumes a modification to the CEV to hold and support a crew of 8. I suspect the L1 refueling will involve a top off of consumables as well. The problem is that the CEV is not only going to bring fresh crews to the cycler, but bring a crew back to earth as well. I really can't see that happening in the CEV by itself.

A shuttle would require a sizable, though short term hab. A Bigelow or TransHab should be both light and cheap, and able to support a crew for a month or two. The the engine is more problematic. You would need a fuel shot, and a crewed shot or two every launch cycle. And the reactors would need to be swapped out every so often. We might be better off launching a fresh nuclear departure stage on a regular basis. Upon return to LEO, the Hab and supporting reusable hardware detach and the unencumbered nuclear components make a final burn to someplace far away from Earth. Mars would be harder. But since we'll be making regular cargo flights anyway adding an unfueled nuclear tug to the manifest wouldn't be too hard. And in the event something goes wrong its not so bad to have a fresh crew go around the loop as it is for a old crew to have to. This is dependent on the ability to bring Mars hydrogen to Mars orbit anyway

As for the difficulty of rendevou I don't think it's impossible to pull of, but it will be considerably more difficult than any we have done before. The craft are going to be docking at a MUCH higher delta-v than we have ever done before. While their relative delta-V's may no be that diffrent (on the other hand to save some propelent they might well be) the high delta-V makes errors in positioning much more critical. An error is twice as big when you go twice as fast.
More critical however is the short and critical time frame to pull it off. Unlike previous docking missions both craft are on a hyberbolic (or nearly hyberbolic) orbits, possibly diffrent ones which only intersect for a limited period of time. Unlike the most previous rendevous missions there isn't an (realitivly) unlimited number of tries you can take before you do it. There is a time window that must be delt with, either you meet it, or you fly into empty space, no fun.
But like you said rendevous is not the only reason you need some sort of abort option. Any malfunction that prevents the docking will cause disaster.

There are many ways to swap crews should a regular docking fail. We could bring The CEV's we launched with, bring the shuttle within a few miles, undock, and try that way. Any cycler is bound to have multiple docks. Even a spacewalk is possible, as both craft are apt to have airlocks.

Another thing to keep in mind is cycler resupply. Even the most closed of closed loop LSSs are going to need resupply. Spare parts, finished experiments, fuel are all going to be needed. But thankfully these are unmanned, and could be done on the longer segments of the flight.

To me the cyler approach seems most like shooting someone out of a cannon to catch a ride on an airplane. Not a very smart thing to do.

Sounds like an episode of Fear Factor.

Remember, we are talking about people who willingly strap themselves to things containing millions of pounds of high explosives.

BWhite · 2005-11-14 14:48:07

I have long believed that a cycler should be built as a variant of an L5 floating space settlement. Visualize an L5 "City in Space" flying free return trajectories between Earth & Mars. A small shuttle carries passengers and freight to the city.

That said, this would be a bit further down the road. Like next century, perhaps?

= = =

Just for fun, visualize tether technology being used to pick up packages and crew capsules as the cycler city zoomed by. Deploy a long flexible tether in front of the city as it approaches. Small rockets should be sufficient to carry a tether a few kilometers ahead of the onrushing cycler.

This allows more than an a single instant to grabble and attach, allowing the shuttle to match course and velocity only approximately.

Attach firmly to the keel of your spacecraft and wait for the acceleration.

Edit: Once attached, reel in the shuttle. Just like 19th century trains picked up the mail from remote stations, all without stopping.

Austin Stanley · 2005-11-15 04:46:48

I have long believed that a cycler should be built as a variant of an L5 floating space settlement. Visualize an L5 "City in Space" flying free return trajectories between Earth & Mars. A small shuttle carries passengers and freight to the city.
That said, this would be a bit further down the road. Like next century, perhaps?

Not a bad idea, but definetly quite a bit further down the road from where we are today.

Just for fun, visualize tether technology being used to pick up packages and crew capsules as the cycler city zoomed by. Deploy a long flexible tether in front of the city as it approaches. Small rockets should be sufficient to carry a tether a few kilometers ahead of the onrushing cycler.
This allows more than an a single instant to grabble and attach, allowing the shuttle to match course and velocity only approximately.
Attach firmly to the keel of your spacecraft and wait for the acceleration.
Edit: Once attached, reel in the shuttle. Just like 19th century trains picked up the mail from remote stations, all without stopping.

The only problem I have with this is the diffrence in speed here is quite severe, which could lead to problems with the intercept. It's not like the mail trains of the 19th century where the diffrence in speed was like what 60mph at best? We are talking about diffrences of ~2km/s here bettwen a typical Earth LEO and a Free Return Orbit. That's more than 4,000 mph. Instead of train trying to snag the mail, it's more like the renentering Space Shuttle trying to snag the mail.

Orbital rendevous is difficult at velocities that are realitivly equal. It takes hours. At these speeds you would have mili-secounds. It would be like trying to intercept a bullet. And the sudden impact of a cable/hook/whatever would be considerable. This is considerably faster than your average rifle bullet (~1km/s) and the assembly would mass several orders of magnitude more. If you did manage to catch the hook, the resulting acceleration would be monsterous. Even if you could spread the acceleration out over say a minute, you would still be pulling >30G's. Obvioulsy your cable would have to be incredibly strong as well.

------

But I don't want to sound entirely opposed to the idea, I have a though about how it might work. The key is that you don't want to slow down the cycler (cause that's the point) and you don't want to speed up the shuttle (cause it's dangerous and heavy). So you slow down the cable! It's light and non-critical. You spool out a length of cable attached to a small rocket and send it of away from your direction of flight, decelerating it. Your shuttle docks with this (simpler since it's not traveling a 2km/s relative to you). You then tell the cycler to slowly slow down the rate at which the cable is unrolling, letting you accelerate more gently. Finaly once you have caught up to the cycler, you are reeled in as normal.

The problem here is that you are going to need a LOT of cable, sevral 100km at least, maybe alot more >1000km?? Which would be heavy.
::EDIT:: And you need to be able to spool cable out a 2km/s to, that could be tough. ::EDIT::

I know you like the spinning tether idea, maybe the cycler could be of such a design, with a large, long tether spinning opposite to it's direction of flight?

Austin Stanley · 2005-11-15 05:07:26

Sorry for the double post, forgot about Commodore here.

Buzz seemed to think that the CEV launch, L1 refueling, and rendevou could be done in 10 days. That assumes a modification to the CEV to hold and support a crew of 8. I suspect the L1 refueling will involve a top off of consumables as well. The problem is that the CEV is not only going to bring fresh crews to the cycler, but bring a crew back to earth as well. I really can't see that happening in the CEV by itself.

Hmm... I guess I have to read the article, because what you are saying doesn't make sense to me. Does the cycler stop somehow at L1? Does the shuttle meet it stoped at L1 or does it rendevous with it out in space? I guess most importantly, how and where does the shuttle match orbit with the cycler?

I agree with what you are saying though. The current CEV won't cut it.

A shuttle would require a sizable, though short term hab. A Bigelow or TransHab should be both light and cheap, and able to support a crew for a month or two. The the engine is more problematic. You would need a fuel shot, and a crewed shot or two every launch cycle. And the reactors would need to be swapped out every so often. We might be better off launching a fresh nuclear departure stage on a regular basis. Upon return to LEO, the Hab and supporting reusable hardware detach and the unencumbered nuclear components make a final burn to someplace far away from Earth. Mars would be harder. But since we'll be making regular cargo flights anyway adding an unfueled nuclear tug to the manifest wouldn't be too hard. And in the event something goes wrong its not so bad to have a fresh crew go around the loop as it is for a old crew to have to. This is dependent on the ability to bring Mars hydrogen to Mars orbit anyway

If you are spending this much refurbishing/refuling the shuttle. Why not just spend that money on refurbishing/refuling a traditional interplantary transfer vehicle (ITV) instead? The engines an ITV would require aren't that diffrent (a little bigger) than those the shuttle would need, and it's Hab is only say, 4 times as big? LSS system requirments fairly similar and what not.

There are many ways to swap crews should a regular docking fail. We could bring The CEV's we launched with, bring the shuttle within a few miles, undock, and try that way. Any cycler is bound to have multiple docks. Even a spacewalk is possible, as both craft are apt to have airlocks.

Sure, but my point is if something goes wrong with docking (a broken hatch on the CEV for example, that would be tricky) your dead. Missing your orbit would be another no-solution docking killer.

Another thing to keep in mind is cycler resupply. Even the most closed of closed loop LSSs are going to need resupply. Spare parts, finished experiments, fuel are all going to be needed. But thankfully these are unmanned, and could be done on the longer segments of the flight.

Resupply doesn't worry me that much. A solar sail or ion tug could eventualy catch up with the cycler and resupply it. This does add additional costs to the system though.

To me the cyler approach seems most like shooting someone out of a cannon to catch a ride on an airplane. Not a very smart thing to do.
Sounds like an episode of Fear Factor.
Remember, we are talking about people who willingly strap themselves to things containing millions of pounds of high explosives.

Even those millions of pounds of high explosives have an abort option (minus the shuttle), the cycler does not.

Of course I'm sure you could find some people quite willing to be shot out of a cannon onto an airplane if you made them the right offer. (Like being on Fear Factor).

RobertDyck · 2005-11-15 18:37:06

I checked the stores, the December issue of Popular Mechanics isn't available. Actually no issue is on store shelves right now, so the December issue should be out shortly. But it's half-way through November and we're talking about the December issue; do you have a time machine?

I've heard of Buzz Aldrin's idea before. Originally he wanted to put a cycler in a permanent Hohmann orbit between Earth and Mars; perihelion at Earth orbit, aphelion at Mars orbit, and co-ordinated to pass by each planet. It sounds nice, no fuel required for each trip and the extra space, rotation for artificial gravity, and long duration life support systems are all reused permanently. But there are several problems:
• launching it in the first place
• getting an Earth shuttle up to it to transfer crew
• getting crew off at Mars
• waiting for the cycler to come back to Mars for the return trip
• getting a the crew back up to it again
• getting crew off at Earth

Buzz's later designs used a modified orbit to change when it rendezvous with Earth or Mars.

I still think it's far more practical to use what Kim Stanley Robinson called a "Permanent Shuttle" in his Red/Green/Blue Mars books. That works by transferring between Low Earth Orbit and Mars orbit, using aerocapture to enter planetary orbit and aerobraking to reduce orbital altitude, and leaving the vehicle parked in planetary orbit to off-load crew and cargo, refuel, and to load crew and cargo for the next trip. Because Mars has lower gravity you could park in higher and more elliptical obit than at Earth. Furthermore, Earth's thick atmosphere demands a shuttle that makes maximum use of the atmosphere, so will have very little on-orbit manoeuvring capability while the Mars shuttle will be more of a rocket so more orbital manoeuvring ability. The Van Allen belts of Earth mean the vehicle must park within them; Mars has no radiation belts.

NASA's Design Reference Mission (DRM) has been nick-named Mars Semi-Direct. That mission architecture calls for an Interplanetary Transit Vehicle (ITV) to be assembled in Earth orbit, then travel from Earth orbit to Mars orbit and back. A couple years ago I tried to update Mars Direct and ended up with something similar to DRM, but not exactly the same. I called Mars Orbit Rendezvous but I've heard it called Mars Hybrid Direct. It wasn't my intention to create a hybrid of Mars Direct and DRM, it just ended up that way. My idea makes the ITV reusable. Initially with expendable TMI and TEI stages, but the propulsion stage can be replaced with a reusable one once developed. Attach it by simply docking. Again, my plan initially uses the Mars Ascent Vehicle (MAV) as the TEI stage.

I actually gave a presentation of my ideas at last summer's Mars Society conference. You can view a copy of my PowerPoint presentation here. You won't be able to view it unless you have PowerPoint installed. If you do, then save it on your computer and open rather than simply clicking on the link. If you click the link you will only view slides within your browser. By opening the file, within PowerPoint you can click "View" and "Notes Pages" to see the embedded presentation notes. Or if you can see my presentation on the conference DVD "Getting There: New Launch and Propulsion Technologies Part 1", second presentation on the disk. (I was way too nervous. And I look middle-aged and heavy. I need to go back to the gym.)

publiusr · 2005-11-16 16:38:40

Buzz didn't push HLLV enough in his POP SCI piece. One picture and that was about it.

MarsDog · 2005-11-20 19:14:16

"The cycler essentially is in orbit around the sun and makes regular flybys of Earth and Mars"

Re useable life support systems make the cycler economical for people.
For heavy supplies and equipment, the cycler is not needed.

Like ocean liners and battleships, the cycler will become a symbol of national pride.

Very good article. Aldrin's vision will prevail because of large scale efficiency.

PurduesUSAFguy · 2005-11-20 21:47:33

"The cycler essentially is in orbit around the sun and makes regular flybys of Earth and Mars"
Re useable life support systems make the cycler economical for people.
For heavy supplies and equipment, the cycler is not needed.
Like ocean liners and battleships, the cycler will become a symbol of national pride.
Very good article. Aldrin's vision will prevail because of large scale efficiency.

But it's not really, efficent, at least not initally, it doesn't work to get large mass payloads to the surface. If you have an established base with all the infrastructurr your going to want up and going, sure a cycler would be a great way to cut down the travel cost of getting personel to Mars, but prior to that the only thing it brings to the surface is a small crew lander, not enough for the 18 months you'll be on the surface. Also I don't understand putting off the first manned landing with the short stays on phobos as listed in the article...not to mention that it puts the first human mission to Mars lasting over 10 days into almost 2040.

The only way we are going to get to Mars (knock on wood) before 2035 is if we go without needing lunar infrastructer in place. Let us also not forget the fact that the in space transfer of cryogenic propellant is a capablility that has yet to be developed...it needs to be at some point, as dose lunar and martian propellant production with orbital propellant depots. But first things first lets get a basic manufactoring capability and out post on Mars before we start worrying about L3 refueling and cyclers.

GCNRevenger · 2005-11-21 07:46:21

Ultimatly, cyclers like Aldrin's have one fatal, un-fixable flaw that precludes their use as an effective crew carrier in the long term: they're slow.

Due to their orbital mechanics, there is no way they can compete with an advanced nuclear propulsion system like GCNR, NSWR, or VCR/VASIMR, which will offer far shorter trip times and will undoubtably become the method of choice.

MarsDog · 2005-11-21 14:11:06

Shuttle had 2 out of 113 failed missions. A number of Martian probes were lost.
Safety favors the cycler. Because of large size considerable redundancy is possible.
Extra safety and possible abort could be designed into the takeoff and landing modules.

------------------------------------------------------------

Some safety thoughts
http://www.futurepundit.com/archives/000940.html

Technologies that would offer greater than order-of-magntitude improvements in safety and reliability can not be retrofitted into existing designs.

Dook · 2005-11-21 15:20:24

Safety favors the cycler???

Really? What is the cycler's safety record over 113 flights?

MarsDog · 2005-11-21 17:07:03

Each module is designed for the same reliability,
and there would have to be multiple failures before a fatality.

http://ourworld.compuserve.com/homepage … aldrin.jpg

If you had 20% chance of failure of single module design.
Then with 4 modules, your chance of death decreases to 0.16%
Down from 1 in 5 to 1 in 625.

GCNRevenger · 2005-11-21 17:53:24

"possible abort could be designed into the takeoff and landing modules. "

Not really, because the amount of fuel you need increases exponentially with the size of your delta burn. You have to basically use the same amount of fuel to get from wherever you are to wherever you are going, the only difference being you are going to dock with the cycler and ride on it. Using the cycler saves you essentially zero rocket fuel, what it does save you is from needing as big of a ship.

To bring along enough fuel for a direct abort back to where you came from quickly enough that your small ships' supplies would hold out would require you to basically slow back down again after you sped up to transit velocities and probobly then some to get back into orbit or on the ground.

It takes an aproximatly equal quantity of chemical fuel or 2/3rd as much for simple nuclear engines to push a ship from Earth orbit to Mars orbit, which would be about the amount you would need to dock with the cycler. Now, if your ship weighs 40MT and you need 40MT of fuel to just accelerate, then you are going to need ~1,000MT of fuel (roughly) to accelerate and decelerate to get home in the event of a fast emergency abort. The rocket equation's a real killer, ain't it?

So no, its not really practical to put an emergency abort fuel supply for a fast return.

The rendezvous with the cycler will not be a worry-free proposition either, and will be quite difficult given its high velocity. If you burn your engine just slightly too long or too short, then you could likly miss completly. Whats the reliability for that?

And then there is the actual docking operation, which itself contributes to the risk by adding even more failure modes.

The cycler itself has a number of inherint drawbacks, the cheif among them is how do you build and accelerate something that big? Its going to take an awfully big push and ISS-scale construction. It is also slow, and cannot made to be fast, thus the passengers will be stuck in the cycler for months. And, since your power/life support/etc has to operate for much longer between ports of call, you have a proportionatly higher possibility of failure.

Compare this to a high-energy NSWR or GCNR ship, which should be able to reach Mars in only a month or two, and carry enough fuel for direct low-energy abort thanks to their high Isp, or push a relativly huge amount of payload slowly to Mars.

It is clear that investing in a high-energy nuclear engine is the better choice then messing around with slow, dangerous cyclers, which don't solve the payload-to-mars problem at all either.

Commodore · 2005-11-21 19:41:32

The advantage of a cycler is it big enough to be largely self-sustaining, with the capability to grow food, have simulated g, and support large crews comfortably. In other words negate most, if not all of the downsides of a long trip.

Also, there is simply no way that sending a relatively small shuttlecraft to meet up with the cycler is going to use anywhere near as much fuel as the comparitively much larger conventional craft. To meet up with it all you need to do is enter an eliptical earth orbit that happens meet with the cycler for the required amount of time. From there is a matter of very small changes, depending on your choosen method. That way if you miss, your going to swing around anyway. A small burn will let you aerobrake. Granted, your going to need a hell of a push to deploy the cycler to begin with, but spread that out among several, if not dozens of cycles, its a bargain. I believe the point is that the speed is maintained via gravity assist on every planetary approach, thus there is little loss of speed.

The biggest cost of a cycler is setting up the infrastructure at both ends to operate your shuttle craft, and the cycler itself. Ultimately I think the people that control the purse strings will stomach a high starting cost better (going to Mars is suppose to be hard) than moderately high recuring cost (shouldn't this be getting easier (yes)).

GCNRevenger · 2005-11-21 20:18:46

"all you need to do is enter an eliptical earth orbit that happens meet with the cycler for the required amount of time"

No. You not only must make an orbit that coincides with the cyclers' trajectory, but you must match velocity with it. Otherwise, all your passengers are going to be able to do is wave at the cycler out the window as it speeds past you.

The trouble is, that the cycler will be on a path that will take it out of orbit at a particular port of call considerably above escape velocity at all points during its approach, and therefore, so must your transfer shuttle. So, there is no "eliptical orbit" that would permit you to easily return should rendezvous fail. This is unavoidable.

Why bother with trying to "mitigate" a long trip if you can have a short trip instead, particularly with the added bennefit of fuel-efficent "slow" cargo ships? Buzz Aldrin simply has not internalized the truth about how a high-energy propulsion system with short travel times would completly rewrite the rules, and he is still firmly entrenched in Von Braun-style thinking... which, with the fruition of one the several practical super engine concepts, is simply obsolete.

MarsDog · 2005-11-21 22:03:57

"possible abort could be designed into the takeoff and landing modules. "
Not really, because the amount of fuel you need increases exponentially with the size of your delta burn. You have to basically use the same amount of fuel to get from wherever you are to wherever you are going, the only difference being you are going to dock with the cycler and ride on it. Using the cycler saves you essentially zero rocket fuel, what it does save you is from needing as big of a ship.
To bring along enough fuel for a direct abort back to where you came from quickly enough that your small ships' supplies would hold out would require you to basically slow back down again after you sped up to transit velocities and probobly then some to get back into orbit or on the ground.
It takes an aproximatly equal quantity of chemical fuel or 2/3rd as much for simple nuclear engines to push a ship from Earth orbit to Mars orbit, which would be about the amount you would need to dock with the cycler. Now, if your ship weighs 40MT and you need 40MT of fuel to just accelerate, then you are going to need ~1,000MT of fuel (roughly) to accelerate and decelerate to get home in the event of a fast emergency abort. The rocket equation's a real killer, ain't it?
So no, its not really practical to put an emergency abort fuel supply for a fast return.

Excess fuel could be used to top up the cycler and to decelerate the landing module.
The takeoff module could make the round trip and become the lander on Earth return

The rendezvous with the cycler will not be a worry-free proposition either, and will be quite difficult given its high velocity. If you burn your engine just slightly too long or too short, then you could likly miss completly. Whats the reliability for that?
And then there is the actual docking operation, which itself contributes to the risk by adding even more failure modes.

No fatal accidents so far with the spacestartion.

http://www.iaanet.org/p_papers/chap5.html
The interplanetary velocities added at Earth and Mars, respectively, are only about 1/10 of each planet's velocity.

One tenth of 30 km/sec and 25 km/sec - comparable with escape velocity from the Moon.

The cycler itself has a number of inherint drawbacks, the cheif among them is how do you build and accelerate something that big? Its going to take an awfully big push and ISS-scale construction. It is also slow, and cannot made to be fast, thus the passengers will be stuck in the cycler for months. And, since your power/life support/etc has to operate for much longer between ports of call, you have a proportionatly higher possibility of failure.

Best power might turn out to be nuclear. Economy of size, as on an aircraft carrier. Solar, ion assist etc.

Compare this to a high-energy NSWR or GCNR ship, which should be able to reach Mars in only a month or two, and carry enough fuel for direct low-energy abort thanks to their high Isp, or push a relativly huge amount of payload slowly to Mars.
It is clear that investing in a high-energy nuclear engine is the better choice then messing around with slow, dangerous cyclers, which don't solve the payload-to-mars problem at all either.

You are correct, austere, optimal design, direct, will get the most mass to Mars quickly.

However
The cycler enthusiasts, including myself, conceive of flexible space platforms.
Large numbers of people would be involved.
Not quite Star Wars or Tube worlds, but a solid step in occupying the solar system

GCNRevenger · 2005-11-22 11:02:31

Cycler enthusiasts are... wrong headed

It makes no sense to make a transit shuttle with 1000-1500MT of rocket fuel, no sense at all, because you could build a 500-700MT (dry) ship with aerobraking of the same mass instead of a 40MT ship with cycler abort fuel. Either the shuttle does not carry abort fuel, or else it would be of a truely absrud size. The whole point of having a cycler is to save fuel by having a smaller ship, but if you pack even a fraction of the fuel needed for a fast abort, the shuttle is going to be bigger then the cycler is.

There is also no possible way for a cycler to use several thousands of tonnes of fuel from the left over abort fuel, obviously, if for no other reason then it would have to burn most of it to drop that fuel into orbit at your destination.

The difference between Shuttle rendezvous with ISS and a transit shuttle rendezvous with a cycler is simple: you only get one shot. If you miss, no shuttle of practical size could abort back quickly without an absurd amount of fuel.

"Large numbers of people involved" is an irrelivent red-herring, because you could move many more people per tonne of ship with even a chemical powerd rocket going directly to Mars burning the fuel a transit shuttle would need for abort, much less high-energy nuclear.

Cyclers are not flexible, you are just using that as a buzz word, and infact they are woefully inflexible because of their innability to depart at will, their low speed, and lack of practical abort options. The initial investment to build them would yeild far more results going to GCNR/NSWR/VASIMR research.

Cyclers are anything but solid, they are a bad investment.

Austin Stanley · 2005-11-22 19:34:17

http://www.iaanet.org/p_papers/chap5.html
The interplanetary velocities added at Earth and Mars, respectively, are only about 1/10 of each planet's velocity.
One tenth of 30 km/sec and 25 km/sec - comparable with escape velocity from the Moon.

I think GCRN responds well to most of this, but I take issue with this point. Sure the diffrence in relative velocity of Earth and Mars is not that great when compared to other quantities, such as the planets orbital velocity or even the energy need to enter orbit. And thus the necessary Delta-V may seem deceptivly small when compared to these figures.

However, that does not change the fact that a diffrence of 2-5km/s bettwen a object in a normal Earth/Mars orbit and a Cycler on it's free return orbit is alot. A heck of a lot. In some of the better case senarios we are talking about a diffrence of like Mach 15 in speed, some 18,000 kph or 11,000 mph. This is REALY fast. The fact that this diffrence is speed is small in comparison to the orbital velocity of the planets is inconsiquental. You can't dock at these speeds, it's not even close to possible. You MUST match velocity with the cycler, and this takes about the same amount of fuel as it would to go to Mars in the first place.

GCRN disccused the amount of fuel necessary for an abort option, but realy it's not practicle. That same amount of fuel could send you to Mars and back. So realy your only options are Dock or Die.

I stand by my earlier analogy, it's like trying to board an airplane by being fired out of a cannon.

SpaceNut · 2006-01-25 07:30:33

A refresher on his plan Buzz backs Mars mission

A plan to colonise Mars — by hitching a ride on a spacecraft built to perpetually circle the Sun. Once in place, the craft, which he calls a Cycler, would follow a 26-month flightpath around the Sun, taking it past Earth and Mars.

This allows for a 44 month stay on mars between cycles. A 5 month passage to the red planet and lots of room not available in the out going ship to mars.

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