Surface centrifugue for a Mars colony

SpaceNut · 2013-12-29 09:48:50

After reading the links I would say that the option for outbound are of little consquence as it is correctable but the stay and return that effects the health the most needs corrective measures for the mission.

I thinking that a node with the sleep quarters at oposite ends of an arm that extends away form the core of the rocket. such that the rocket points the way to where we are going.

The surface I think we will need something even for the first crew as the stay is so extreeme when compared to the other parts of the mission. So how do we design this from a minimal amount of items shipped from earth as we can ill afford the cost.

Tom Kalbfus · 2013-12-29 10:06:24

GW Johnson wrote:

The three things I always see proposed for artificial spin gravity are (1) gigantic battlestar galacticas that spin about longitudinal axes, (2) cable-connected lightweights, and (3) truss-connected battlestar galacticas.
Battlestar galacticas are not practical at all at this time in history: too expensive, in all senses of the word. That eliminates ideas (1) and (3).
Idea (2) is almost practical, except for instabilities and difficulties spinning up and spinning down, the transients. Otherwise, it looks pretty good steady-state. Proposing to do this with two relatively tiny capsules ignores both living-space-to-stay-sane and radiation shielding for a long voyage (6 months or more 1-way to Mars). You can better do this with a proper habitat module at one end of the cable, and something else heavy at the other end (maybe the propellant and engines you have to have, anyway). God help you if the cable breaks (meteroid impact!!!), because no one else can.
Because of the need to do course corrections, there will be more than one very difficult-to-execute spin-up and spin-down operation. More than one of each maneuver vastly increases the probability of an accident, because these probabilities multiply, they do not add. That is why rigid structures are very much preferred for spin gravity designs. Much lower probability of a transient spin-up or -down instability accident.
There is a 4th idea that can address all of this successfully, which can easily be implemented with multiple docked propellant tanks, far more easily than with bigger stages. Using a combination of serial and parallel docking configurations, you can always create a long baton, fatter or skinnier as the number of tanks changes, with the hab at one end and the engines at the other. This structure is at least semi-rigid, quite unlike cable-connected assemblies. The spin-up/spin-down risks are therefore way-to-hell-and-gone lower than any imaginable cable-connected system. Doing course corrections is thus way less risky with a more rigid spinning structure, and the baton shape is well known to be quite stable while spinning (see the twirlers at any football game Friday nights all over the US).
The trouble with idea (4) (spinning baton) is that it is inherently not amenable to the overly-minimalist configuration proposals. I don't see that as a serious objection, because those overly-minimalist proposals ignore the living space and radiation protection issues. Either is likely to kill crews, more especially the solar flare radiation. But insanity also kills, as we have seen for a long time now with mass shootings by people known to have mental problems. Ask anyone who has ever served time in solitary confinement about its effects on sanity. He will confirm what I say about long-term confinement in quarters too close.
Overly-minimalist proposals being infeasible on the confinement and radiation-protection issues, I don't see any realistic objection to using the modular ship idea to provide a spinning baton shape for artificial gravity. Its only problem is that we are forced to design for 1 full gee at the farthest hab deck, because we do not have one single shred of direct evidence that partial gee will be sufficient. 1 full gee at 4 rpm requires 56 m radius, scale your ideas from there. We already know how to build things that docked-module way: ISS is also docked modules, and the Saturn-1 first stage had parallel-connected tanks, and we do strap-on boosters.
Any spacious hab design will have the room to add water and wastewater tankage in such a way so as to provide a 20 cm water shield around at least part of the hab as a radiation shelter. Could be externally or internally mounted. Lots of design freedom there.
I would suggest using Bigelow-syle inflatables to be docked together to create a really big hab module. I would also suggest that the packaged core equipment in each module be deployed in such a way as to remain within the core space of the fully-erected inflatable structure. That way, access to the pressure shell is unimpeded, for rapid repair of meteroid punctures. You cannot afford the time to move stuff out of the way: it'll depressurize before you can patch it if you clutter the pressure walls. That same free-access consideration applies to rigid-shell hab modules, too. Basic safety "at work" here.
I would also suggest that the vehicle control station be the radiation shelter. That way critical maneuvers may be performed no matter the solar weather.
None of this would yet apply to a surface hab on Mars. But depending upon what we finally learn about "how much gee is enough", we might have to add some sort of spinning frisbee shape as part of permanent settlements on Mars and the moon. No one knows yet. We can solve that problem if and when it crops up.
Just ideas and suggestions from an old, and very widely-experienced, aerospace engineer.
GW

One configuration for space would be a series of modules with flexible connector tubes. For a wheel that is 100 meters in radius, the total length of the train of modules would be 628.32 meters long, lets say that each module is about 50 meters long and connected to the one behind it and in front of it by a flexible link such as would be used in connecting the cars of a train. the propulsive module and fuel tanks would be in front, the cargo and crew areas would be in back and pulled through space by the ship's engines, the with the rocket motors pointed to miss what it is towing. When this flexible train ship is not accelerating the back is linnked up to the front to form a circle, then small rocket motors would then spin it up for gravity, basically chasing its tail in a circle. When more maneuvering is required, slow down the spinning and unlink the front from the back. When Mars orbit is reached some of the modules are detached and become habs or landers for landing on Mars.

GW Johnson · 2013-12-29 11:37:26

The volume, mass, and/or number of propellant tank modules in any design far exceeds the volume, mass, and/or number of all other types of things, in any conceivable Mars ship, chemical or nuclear. The only thing needing artificial gee is the crew hab, which is 1, 2, maybe 3 of these small components. That being the case, I saw no reason to build a spinning wheel for a habitat. That way lay "battlestar galactica" stuff.

What I came up with was something about the same volume allowance as the old Skylab for a crew hab, with a crew of 6. That's twice the crowding the old Skylab crews of 3 saw, but still spacious compared to Mir and ISS. I did a combined parallel-series stackup of propellant modules to achieve a length between about 100 and 200 meters, with pusher engines at the tail end. It spins like a baton end over end to put 1 full gee at the farthest crew deck, less at higher decks, but still over half a gee. The whole ship was in the 300-500 ton class, but assembled of modules small enough to launch with Atlas-5, Delta-4, and a few Falcon-Heavies.

No need for a hugely-expensive SLS. It's tonnage to launch multiplied by unit launch cost (per unit mass of payload), which is only low if the launcher flies fully loaded. You launch all this tonnage at the anticipated unit costs for SLS, and the economics become politically unsustainable, no matter what size objects you launch. $1000-2500/pound is something we can tolerate. 10,000/lb is not. Period. I see no point to an SLS-class launcher until commercial space sees a need for it, and does it at well under $1000/lb. And someday, they will. But not in the next several years.

The landers went separately, each pushing the landing propellant supplies as dead-head cargo. These went unmanned and unspun. Still modular, using exactly the same common propellant tank modules as the manned ship. I did not rely on in-situ propellant, and I did not jettison so much as a single tank into deep space. I recovered every single item in my design for reuse or salvage, either at Mars or in Earth orbit. No free return, either. So my mission design represents a generous upper bound on what has to be launched and assembled. The three unmanned ships, pushed by the landers themselves, were in the 1000 ton class, each. That's in the neighborhood of 4000 tons that has to be launched and assembled. A nuke would be around half of that, this was a LOX-LH2 chemical rough-out.

This verges upon "battlestar galactica" problems, yes, but it also accomplishes much more than most mission plans I have seen. I budgeted the propellants from Earth to spend the first 5 or 6 months at Mars making 6 separate landings plus a visit to Phobos from low Mars orbit. The best site explored (presumably with lots of massive buried ice to mine), would be selected for a base. The remainder of the year at Mars would be spent there at the best site, building that base, all 6 on the surface with all 3 landers. If the ISPP actually works at the base site, it produces the extra propellants to support suborbital lander flights to explore additional sites. Icing on the cake, it would be. But we get a huge return, even if it doesn't work. Including a functioning base waiting for folks to return on the next trip.

As I said, an upper bound. You get exactly what you pay for. But you must also remember that nothing is as expensive as a dead crew. So, don't be too cheap. Cheap kills. We've already seen it.

GW

Tom Kalbfus · 2013-12-30 13:30:54

Just one thing I might mention the 628.32 meter long space train was for an interplanetary vehicle that was spun for a full Earth g, if you cut that length down to a third, about 210 meters long, you can spin it at the same rate to simulate Mars gravity. You can reduce the number of modules from 12 to 4, but you should probably cut the length of each module to 25 meters and have 8 modules this way you can have the entire spaceship experiencing Mars gravity more or less, and you uncouple the front from the back if you want to break its wheel formation and go into linear formation for space maneuvering.

The advantage of this configuration is you don't have to have part of the spaceship spinning and the other part not, you don't need lubrication for spinning joints. Ok, out of 8 modules, lets say 3 of them house six astronauts, does this sound sufficient to you? The astronauts would experience Mars gravity for almost the entire 2 year length of the mission.

Another advantage is that it would be easier to do EVAs and repair various parts of the spaceship if the entire thing was under Mars gravity, an astronaut could then just walk on the inner surface of the spinning space vehicle in his Mars spacesuit while it is in transit.

Last edited by Tom Kalbfus (2013-12-30 13:36:38)

JoshNH4H · 2013-12-30 16:11:05

On the downside, we won't be sending such large things from Earth to Mars or back for many years after colonization begins

Tom Kalbfus · 2013-12-30 18:27:26

From Wikipedia

The Mayflower departed Plymouth, England on September 16, 1620 with 102 passengers and about 30 crew members in the small, 100 foot long ship. The first month in the Atlantic, the seas were not severe, but by the second month the ship was being hit by strong north-Atlantic winter gales causing the ship to be badly shaken with water leaks from structural damage. There were two deaths, but this was just a precursor of what happened after their Cape Cod arrival, when almost half the company would die in the first winter.[12][13]

So what would be the interplanetary equivalent to the Mayflower, but going to Mars. If you had 102 passengers and 30 crew members, what would such a spacecraft look like? I do think 30 crew members is a bit high, even for a large space craft, but maybe I might be wrong, that would mean about 1 crew member for every 3-4 passengers

louis · 2013-12-30 18:30:26

Tom Kalbfus wrote:

From Wikipedia
The Mayflower departed Plymouth, England on September 16, 1620 with 102 passengers and about 30 crew members in the small, 100 foot long ship. The first month in the Atlantic, the seas were not severe, but by the second month the ship was being hit by strong north-Atlantic winter gales causing the ship to be badly shaken with water leaks from structural damage. There were two deaths, but this was just a precursor of what happened after their Cape Cod arrival, when almost half the company would die in the first winter.[12][13]
So what would be the interplanetary equivalent to the Mayflower, but going to Mars. If you had 102 passengers and 30 crew members, what would such a spacecraft look like? I do think 30 crew members is a bit high, even for a large space craft, but maybe I might be wrong, that would mean about 1 crew member for every 3-4 passengers

I think the equivalent would be an interplanetary shuttle hab - a Bigelow style structure. You pack as many people as you can into the hab, and then the crew get them from Earth Orbit to Mars Orbit. Apollo style landers take you down to the surface at each end.

JoshNH4H · 2014-01-01 01:28:23

Interesting aside-- Even using extremely optimistic figures (Assuming that the available volume was twice the boat's rated tonnage), the Nina, the Pinta, and the Santa Maria had between 5 and 7 cubic meters of space per person for a 35 day journey. The ISS is downright cavernous in comparison, at 150 cubic meters per person.

Tom Kalbfus · 2014-01-01 09:40:22

The Nina, Pinta, and Santa Maria didn't have to recycle their air! Also the travel time from Spain to the New World was only 10 weeks, now a 10 week travel time to Mars would be fantastic, and probably could only be achieved by a nuclear engine.

I think a wheel would be just the thing for transporting 130 colonists to Mars, 30 of whom would act as the crew. Most spacecraft are automated anyway, so it seems doubtful that a crew of 30 would ever be needed.

Last edited by Tom Kalbfus (2014-01-01 09:41:56)

Quaoar · 2014-01-01 09:43:46

GW Johnson wrote:

The volume, mass, and/or number of propellant tank modules in any design far exceeds the volume, mass, and/or number of all other types of things, in any conceivable Mars ship, chemical or nuclear. The only thing needing artificial gee is the crew hab, which is 1, 2, maybe 3 of these small components. That being the case, I saw no reason to build a spinning wheel for a habitat. That way lay "battlestar galactica" stuff.
What I came up with was something about the same volume allowance as the old Skylab for a crew hab, with a crew of 6. That's twice the crowding the old Skylab crews of 3 saw, but still spacious compared to Mir and ISS. I did a combined parallel-series stackup of propellant modules to achieve a length between about 100 and 200 meters, with pusher engines at the tail end. It spins like a baton end over end to put 1 full gee at the farthest crew deck, less at higher decks, but still over half a gee. The whole ship was in the 300-500 ton class, but assembled of modules small enough to launch with Atlas-5, Delta-4, and a few Falcon-Heavies.
No need for a hugely-expensive SLS. It's tonnage to launch multiplied by unit launch cost (per unit mass of payload), which is only low if the launcher flies fully loaded. You launch all this tonnage at the anticipated unit costs for SLS, and the economics become politically unsustainable, no matter what size objects you launch. $1000-2500/pound is something we can tolerate. 10,000/lb is not. Period. I see no point to an SLS-class launcher until commercial space sees a need for it, and does it at well under $1000/lb. And someday, they will. But not in the next several years.
The landers went separately, each pushing the landing propellant supplies as dead-head cargo. These went unmanned and unspun. Still modular, using exactly the same common propellant tank modules as the manned ship. I did not rely on in-situ propellant, and I did not jettison so much as a single tank into deep space. I recovered every single item in my design for reuse or salvage, either at Mars or in Earth orbit. No free return, either. So my mission design represents a generous upper bound on what has to be launched and assembled. The three unmanned ships, pushed by the landers themselves, were in the 1000 ton class, each. That's in the neighborhood of 4000 tons that has to be launched and assembled. A nuke would be around half of that, this was a LOX-LH2 chemical rough-out.
This verges upon "battlestar galactica" problems, yes, but it also accomplishes much more than most mission plans I have seen. I budgeted the propellants from Earth to spend the first 5 or 6 months at Mars making 6 separate landings plus a visit to Phobos from low Mars orbit. The best site explored (presumably with lots of massive buried ice to mine), would be selected for a base. The remainder of the year at Mars would be spent there at the best site, building that base, all 6 on the surface with all 3 landers. If the ISPP actually works at the base site, it produces the extra propellants to support suborbital lander flights to explore additional sites. Icing on the cake, it would be. But we get a huge return, even if it doesn't work. Including a functioning base waiting for folks to return on the next trip.
As I said, an upper bound. You get exactly what you pay for. But you must also remember that nothing is as expensive as a dead crew. So, don't be too cheap. Cheap kills. We've already seen it.
GW

Your modular spaceship looks very intresting: once arrived on Mars, will she insert in orbit propulsively or via aerocapture?
In the last case, do you use some kind of foldable aeroshell on the head module?

GW Johnson · 2014-01-01 11:03:16

Hi Quaoar:

Nope, my design is an old-fashioned "do-it-the-hard-way" design. I used propulsive burns for capture at Mars, precisely because we have not done aerocapture with men anywhere but Earth (coming back from the moon). Our atmosphere is very predictable at entry altitudes (140 km on down to around 30 km). Mars's atmosphere varies by factors of 2 or more at entry altitudes there (135 km on down to 10 or 20 km). That's too variable to trust very much with men. Even probe designs have had difficulties with this variability.

My rough-out design is posted in an article over at http://exrocketman.blogspot.com as the article titled "Mars Mission Study 2013", dated 12-13-2013, if you want to go look at more details. I have updated that article with second thoughts and extra data, and will continue to do so. As posted, it represents an upper bound on the costs for a mission that accomplishes a huge return no matter what happens, with all-chemical propulsion and all reusable-or-salvageable hardware.

When I use the term "rough-out" design, I'm talking about something better than a bounding analysis, but less than a full design analysis. I used the simple rocket equation, with empirical "jigger" factors for drag and gravity losses where applicable (the same sort of stuff von Braun was doing in the 1940's and 1950's to show what is possible before embarking upon real designs, and we all know how that turned out during the 40's, 50's, and 60's).

I used a very old entry approximate analysis originally developed for warheads. I used some very approximate terminal descent kinematics from constant-acceleration physics, modified by intuitive safety factors that hopefully are very conservative.

I did work out the appropriate volumes and shapes to go with my weight statements, just good enough to get realistic diameters and lengths for the vehicles. My volume allowance is near 60-100 cubic meters per person, in both the transit habitat and the lander, but I didn't work out the details of how much is for congregating together vs being alone. I doubled and tripled the typical allowances for for food air and water for the crew, because I think frozen food and water-based cooking are going to be required (the artificial gravity enables this, too).

GW

JoshNH4H · 2014-01-01 11:05:12

Tom- Given that Columbus made a stop at the Canary Islands before sailing in the open ocean, it was actually only 5 weeks spent confined at any one time. For what it's worth, I'm willing to bet that the ships smelled worse than any space capsule, even with their open air.

The amount of space let crewmember was roughly similar to the Gemini or Mercury capsules. Imagine spending 5 weeks in one of those. It's comparable to spending 5 weeks in one of those Subaru station wagon/hatchbacks I see everywhere. Also include 35 days worth of food and water and other supplies, and you see that it gets quite cramped.

For radiation protection reasons, concentrated masses are better than wheels.

GW Johnson · 2014-01-01 11:24:04

A wheel makes sense if all the modules in it are human habitation spaces and the supporting supplies. The central core needs to be the propellants and propulsion. The problem with chemical or even solid-core nuclear propulsion is that the mass and volume of propellants is order-of-magnitude 10^2 (or more) larger than everything associated with the crew. That plays havoc with vehicle layout, and in the past has led to "battlestar galactica" designs from NASA and others that would be completely unaffordable at this time in history. Gigantic truss structures are nothing but inert weight that drives you to gigantic amounts of propellant required, very, very quickly.

In the simple "slim" baton that spins end-over-end, you have multiple decks in each human-habitation module, all at one end. Let them use ladders to get from deck to deck, to get really good and aerobic exercise "all the time". Put the gym and congregating areas in the farthest deck at one full gee, and the working areas just above at near one full gee (yep, there is a strong radial gradient in small sizes, say 100 to 200 meters long). Put the sleeping quarters highest up at the least gee, since the bed rest studies seem to show there is little gee benefit while you are prone asleep. Put the stored supplies above that, at the least gee, usually around 0.5 gee in the designs I have looked at.

Those same considerations would apply to cable-connected spinning designs. I just prefer the semi-rigid baton for enhanced safety and convenience. The downside of the baton is that it requires you to go to a modular approach, so that you can stage-off empties, and then redock/reconfigure your baton. I am afraid of the transients in cable-connected designs: spin-up and de-spin in such structures requires multiple super-well coordinated thrusters operating simultaneously. An accident with a stuck thruster like what happened on Armstrong's Gemini flight would cause loss of vehicle and crew. Plus, what if a meteor cuts the cable while you are spinning? How do you achieve multiple-cable redundancy for things like that? I honestly don't know. But I do know we can dock lots of modules together, and there is a very promising layered foam-and-foil meteor armor that is super lightweight.

I usually allow something on the order of 60 to 100 cubic meters of pressurized volume per person. Some of that is in common areas for congregating or working together, some of that is for private personal spaces in which to be alone. I don't know a figure for that last split, but the overall number is what drives rough-out design analyses, anyway. I do know the longer the confinement, the more space is required for mental health. Planning for a crew to ride all the way to Mars in things as crowded as a space capsule is as insane as the crew would be on arrival. And don't forget, there is confinement while at Mars for about a year , because you cannot run around unprotected outside (so where do they live while there and how big is it?), and there is that long voyage home.

There are a whole slew of things to worry about, planning a voyage like that, and most of those issues have nothing to do with the rocket equation and which Isp you have available, except in how big and heavy your dead-head payloads are.

GW

Last edited by GW Johnson (2014-01-01 11:41:17)

SpaceNut · 2014-01-01 11:54:16

The end over end tummble means that we are not in direct communication, we can not able to avoid objects and that we are spinning blind in the direction of travel.

Quaoar · 2014-01-01 15:53:14

GW Johnson wrote:

Hi Quaoar:
Nope, my design is an old-fashioned "do-it-the-hard-way" design. I used propulsive burns for capture at Mars, precisely because we have not done aerocapture with men anywhere but Earth (coming back from the moon). Our atmosphere is very predictable at entry altitudes (140 km on down to around 30 km). Mars's atmosphere varies by factors of 2 or more at entry altitudes there (135 km on down to 10 or 20 km). That's too variable to trust very much with men. Even probe designs have had difficulties with this variability.
My rough-out design is posted in an article over at http://exrocketman.blogspot.com as the article titled "Mars Mission Study 2013", dated 12-13-2013, if you want to go look at more details. I have updated that article with second thoughts and extra data, and will continue to do so. As posted, it represents an upper bound on the costs for a mission that accomplishes a huge return no matter what happens, with all-chemical propulsion and all reusable-or-salvageable hardware.
When I use the term "rough-out" design, I'm talking about something better than a bounding analysis, but less than a full design analysis. I used the simple rocket equation, with empirical "jigger" factors for drag and gravity losses where applicable (the same sort of stuff von Braun was doing in the 1940's and 1950's to show what is possible before embarking upon real designs, and we all know how that turned out during the 40's, 50's, and 60's).
I used a very old entry approximate analysis originally developed for warheads. I used some very approximate terminal descent kinematics from constant-acceleration physics, modified by intuitive safety factors that hopefully are very conservative.
I did work out the appropriate volumes and shapes to go with my weight statements, just good enough to get realistic diameters and lengths for the vehicles. My volume allowance is near 60-100 cubic meters per person, in both the transit habitat and the lander, but I didn't work out the details of how much is for congregating together vs being alone. I doubled and tripled the typical allowances for for food air and water for the crew, because I think frozen food and water-based cooking are going to be required (the artificial gravity enables this, too).
GW

Thanks very much!

I've noted your landers (and all the rockets of your ship) use LOX-LH2 to save propellant mass: how do you solve the problem of boil-off douring a year long mission?

Tom Kalbfus · 2014-01-01 17:08:28

GW Johnson wrote:

A wheel makes sense if all the modules in it are human habitation spaces and the supporting supplies. The central core needs to be the propellants and propulsion. The problem with chemical or even solid-core nuclear propulsion is that the mass and volume of propellants is order-of-magnitude 10^2 (or more) larger than everything associated with the crew. That plays havoc with vehicle layout, and in the past has led to "battlestar galactica" designs from NASA and others that would be completely unaffordable at this time in history. Gigantic truss structures are nothing but inert weight that drives you to gigantic amounts of propellant required, very, very quickly.
In the simple "slim" baton that spins end-over-end, you have multiple decks in each human-habitation module, all at one end. Let them use ladders to get from deck to deck, to get really good and aerobic exercise "all the time". Put the gym and congregating areas in the farthest deck at one full gee, and the working areas just above at near one full gee (yep, there is a strong radial gradient in small sizes, say 100 to 200 meters long). Put the sleeping quarters highest up at the least gee, since the bed rest studies seem to show there is little gee benefit while you are prone asleep. Put the stored supplies above that, at the least gee, usually around 0.5 gee in the designs I have looked at.
Those same considerations would apply to cable-connected spinning designs. I just prefer the semi-rigid baton for enhanced safety and convenience. The downside of the baton is that it requires you to go to a modular approach, so that you can stage-off empties, and then redock/reconfigure your baton. I am afraid of the transients in cable-connected designs: spin-up and de-spin in such structures requires multiple super-well coordinated thrusters operating simultaneously. An accident with a stuck thruster like what happened on Armstrong's Gemini flight would cause loss of vehicle and crew. Plus, what if a meteor cuts the cable while you are spinning? How do you achieve multiple-cable redundancy for things like that? I honestly don't know. But I do know we can dock lots of modules together, and there is a very promising layered foam-and-foil meteor armor that is super lightweight.
I usually allow something on the order of 60 to 100 cubic meters of pressurized volume per person. Some of that is in common areas for congregating or working together, some of that is for private personal spaces in which to be alone. I don't know a figure for that last split, but the overall number is what drives rough-out design analyses, anyway. I do know the longer the confinement, the more space is required for mental health. Planning for a crew to ride all the way to Mars in things as crowded as a space capsule is as insane as the crew would be on arrival. And don't forget, there is confinement while at Mars for about a year , because you cannot run around unprotected outside (so where do they live while there and how big is it?), and there is that long voyage home.
There are a whole slew of things to worry about, planning a voyage like that, and most of those issues have nothing to do with the rocket equation and which Isp you have available, except in how big and heavy your dead-head payloads are.
GW

What if it were a spaceship train, that is each car of the train was its own seperate spaceship, in this case we'd have 8 speaceships linked together and spinning for gravity, and when they approach Mars, they all seperate and become individual landers each having its own fuel tanks and engines, they just travel together in clusters for gravity, that means for 120 astronauts, there would be 15 in each spaceship. the landers would be habs, that is they would all end up being seperate buildings of the base, that is the entire Mars base would be constructed prefab in Low Earth orbit and each component would have its own seperate engine for getting to Mars, once the transmars injection is accomplihed all 8 of the spaceships would link together to form a wheel and spin for gravity. I believe Von Braun one time talked about having an exploration fleet to explore Mars.

Tom Kalbfus · 2014-01-01 19:57:22

GW Johnson wrote:

A wheel makes sense if all the modules in it are human habitation spaces and the supporting supplies. The central core needs to be the propellants and propulsion. The problem with chemical or even solid-core nuclear propulsion is that the mass and volume of propellants is order-of-magnitude 10^2 (or more) larger than everything associated with the crew. That plays havoc with vehicle layout, and in the past has led to "battlestar galactica" designs from NASA and others that would be completely unaffordable at this time in history. Gigantic truss structures are nothing but inert weight that drives you to gigantic amounts of propellant required, very, very quickly.
In the simple "slim" baton that spins end-over-end, you have multiple decks in each human-habitation module, all at one end. Let them use ladders to get from deck to deck, to get really good and aerobic exercise "all the time". Put the gym and congregating areas in the farthest deck at one full gee, and the working areas just above at near one full gee (yep, there is a strong radial gradient in small sizes, say 100 to 200 meters long). Put the sleeping quarters highest up at the least gee, since the bed rest studies seem to show there is little gee benefit while you are prone asleep. Put the stored supplies above that, at the least gee, usually around 0.5 gee in the designs I have looked at.
Those same considerations would apply to cable-connected spinning designs. I just prefer the semi-rigid baton for enhanced safety and convenience. The downside of the baton is that it requires you to go to a modular approach, so that you can stage-off empties, and then redock/reconfigure your baton. I am afraid of the transients in cable-connected designs: spin-up and de-spin in such structures requires multiple super-well coordinated thrusters operating simultaneously. An accident with a stuck thruster like what happened on Armstrong's Gemini flight would cause loss of vehicle and crew. Plus, what if a meteor cuts the cable while you are spinning? How do you achieve multiple-cable redundancy for things like that? I honestly don't know. But I do know we can dock lots of modules together, and there is a very promising layered foam-and-foil meteor armor that is super lightweight.
I usually allow something on the order of 60 to 100 cubic meters of pressurized volume per person. Some of that is in common areas for congregating or working together, some of that is for private personal spaces in which to be alone. I don't know a figure for that last split, but the overall number is what drives rough-out design analyses, anyway. I do know the longer the confinement, the more space is required for mental health. Planning for a crew to ride all the way to Mars in things as crowded as a space capsule is as insane as the crew would be on arrival. And don't forget, there is confinement while at Mars for about a year , because you cannot run around unprotected outside (so where do they live while there and how big is it?), and there is that long voyage home.
There are a whole slew of things to worry about, planning a voyage like that, and most of those issues have nothing to do with the rocket equation and which Isp you have available, except in how big and heavy your dead-head payloads are.
GW

What if it were a spaceship train, that is each car of the train was its own seperate spaceship, in this case we'd have 8 speaceships linked together and spinning for gravity, and when they approach Mars, they all seperate and become individual landers each having its own fuel tanks and engines, they just travel together in clusters for gravity, that means for 120 astronauts, there would be 15 in each spaceship. the landers would be habs, that is they would all end up being seperate buildings of the base, that is the entire Mars base would be constructed prefab in Low Earth orbit and each component would have its own seperate engine for getting to Mars, once the transmars injection is accomplihed all 8 of the spaceships would link together to form a wheel and spin for gravity. I believe Von Braun one time talked about having an exploration fleet to explore Mars.

GW Johnson · 2014-01-02 14:30:46

The fleet of ships idea dating from the 1950’s was actually Ernest Stuhlinger’s idea, not von Braun’s. (They knew each other.) The ships were to be ion thruster-powered. There were 6 ships, each with a crew of 20, and each carrying one one-shot/throwaway 2-stage chemical lander, for a total of 6 landings. The landers were based on von Braun designs using hydrazine and RFNA. The old Disney “Tomorrowland” program “Mars and Beyond” showcases that Mars mission design concept very well for the public, actually. Not a bad design for what they thought they knew in 1955.

That kind of fleet and 100-something crew would have required thousands of launches to send tens of thousands of tons to orbit, for assembly by hundreds, if not thousands, of other people. Considerably more infrastructure than the fleet’s mass would have to exist in orbit to carry out such a task. It’s just my opinion, of course, but that’s well into the unaffordable “battlestar galactica” realm.

I went “slender baton” with simple module-docking, and 4 ships (3 unmanned) in my fleet, because my crew was only 6. Total fleet mass as assembled was under 4000 tons, and that’s an upper-bound, Cadillac-return mission (6 landings plus a Phobos visit, plus a base at the best site, while there in the one trip). All that you can get while assuming that your ISRU/ISPP does not work at all. If it does work, you get to fly suborbitally to even more landing sites, and your base is quite the attractive place for anybody making a second trip.

These are all things that mission planners really need to worry about. And crunch numbers about. You can do it with something a bit better than a bounding analysis, but less than a full-blown design process / design analysis.

GW

Tom Kalbfus · 2014-01-03 08:24:10

That kind of fleet and 100-something crew would have required thousands of launches to send tens of thousands of tons to orbit, for assembly by hundreds, if not thousands, of other people. Considerably more infrastructure than the fleet’s mass would have to exist in orbit to carry out such a task. It’s just my opinion, of course, but that’s well into the unaffordable “battlestar galactica” realm.

Actually if you read the literature about Battlestar Galactica, it was a ship the size of an asteroid, its crew was much larger than 120. I think its possible to launch a spaceship from the ground carrying 20 people to orbit at a time. The truth is if we continue doing things the NASA way, we are not going to accomplish very much, sending 6 people to Mars does not a colony make. I think if we want to establish a colony, we need to send at least 100 as the Mayflower did.

GW Johnson · 2014-01-03 10:05:46

History says don't plant the colony on the first trip, if you expect it to succeed. It says do the exploration first to find out what all is there, and where exactly it is (and by implication, what quality the resources have). You can also plant a small base or station on that first trip to experiment with adaptation, if your during-the-trip results say things look good. If they don't, you'd better be exploring more than one site, or you won't get to plant that adaptation base. It takes real ground truth to answer the exploration questions. Remote sensing just doesn't hack it, not even today.

By adaptation, I mean using the resources you found to figure out ways and means to live off the land. That station may or may not stay populated permanently, but it is inherently manned by a small crew, since it has to be supported mostly (or entirely) by supplies shipped from Earth. It takes a lot of time in "adaptation" to figure out not just how to survive, but how to thrive. Once you have those answers, then it is time for mass quantities of colonists. It is inherently impossible to predict how long it will take to get those answers, even working at "best possible speed".

Actually, I quite agree with the notion that we could send up dozens of folks at once, right now. The 53 ton payload of Falcon Heavy would support such a manned transfer vehicle surface-to-LEO. But it is premature to send that many people to Mars (or even to the moon). A small crew needs to spend months-to-years figuring out how to make our ISRU/ISPP equipment really work well, and all the rest of adaptation, which goes far beyond our current concepts for ISRU/ISPP.

Even then, the problems of water, air, and propellants with ISRU/ISPP pale in comparison to the problems of growing food, mainly because we don't yet know how to build large pressurized buildings on Mars from local materials. Especially considering that (1) radiation protection at one level or another will be required of that vacuum-proof building, and, (2) its windows must let in the right portion of the light spectrum (some but not too much ultraviolet). We are just starting to develop designs for ISRU/ISPP. Nobody has any credible building designs yet. What are you going to use for concrete, for example? Some of these must be greenhouses, others residences. Not the same design at all.

And there are a whole plethora of infrastructure problems yet to be solved for any colony to thrive, not just survive. What kind of surface transport do you use? How do you build roads? How do you make steel? Aluminum? Plastics? Concrete? Etc? Some of us are talking about those things on this forum. But there are no credible designs or processes undergoing even early experimental trials yet. Just some laboratory benchtop stuff, and only for a very few of the many issues we have to resolve for a successful colony.

Nope, planting a colony is premature. We need to finish the exploration (started by robot probes), and start the adaptation process (which needs that surface base/experiment station).

GW

Last edited by GW Johnson (2014-01-03 10:10:18)

Tom Kalbfus · 2014-01-03 11:42:18

I think a 100 person colony could find out those answers a lot quicker than a 6 person base. Growing food would require a larger population. I think colonization will be determined by technological developments. the NASA era of space exploration is coming to a close, where very expensive missions are financed by Congress. I think a colony will be the result of a commercial enterprise. People will want to settle there to stake a claim start a new society. I think the era of expensive government mounted manned missions to planets is coming to a close. I think the time is running out to mount an Apollo style mission, which is about to be over taken by a bunch of private interests.

I think we're getting close to a human lifetime since astronauts last walked on the Moon, something is going to happen in that time. I expect that by 2033, 66 years since Apollo, things will be different.

Last edited by Tom Kalbfus (2014-01-03 11:46:17)

Quaoar · 2014-01-03 11:54:30

GW Johnson wrote:

Nope, planting a colony is premature. We need to finish the exploration (started by robot probes), and start the adaptation process (which needs that surface base/experiment station).
GW

Probably it will take 50-100 yr., starting from the landing of the first mission. For the beginning, I imagine a little base with modula habitat and a rotating crew, living of food and water imported from Earth, but making experiments on growing crops in an enflatable geenhouse and starting using local matherial, like trying to make glass melting sand, and to make briks mixing water and regolth.

Do you think ISPP may work for the first mission, or it will better to realy on an orbiting ERV and land only the habitat and a little ascender with the propellant bringed from Earth?

Last edited by Quaoar (2014-01-03 11:58:29)

GW Johnson · 2014-01-03 14:02:53

Hi Quaoar:

To answer your questions, (1) I think a small-crew base could answer a lot of the adaptation questions in a lot less than 50 years. Although Tom disagrees, I don't think it would take a 100+ population to do most of that. But in practical reality, the adaptation base would slowly grow with time, anyway.

(2) I have come to think in recent months that we ought to start from orbit with smallish landers, and then also go to the surface and establish an adaptation base, all in that first mission. To do that smartly, with maximum probability of success, means that first mission ought to explore multiple sites to get real "ground truth" before establishing the the adaptation base at the "best" one. Multiple landings requires orbital staging (and a reusable one-stage lander), while you need to land everything and everybody at one site to establish a real base of any kind. So, do both in the one mission, as it is very, very, very unlikely in the extreme that a government agency of any nation, or even a consortium of government agencies, will ever fund more than one mission.

Tom disagrees with me, but I don't really believe the private entities will, in the next century or so, establish on Mars any sort of settlement, colony, or even just a base, until the necessary ground truth has been obtained by government(s) to let them plan their enterprise. That's just the nature of private companies, and it has been true for at least 500 years now. (The flip side is that there will be no continuity in the management of that adaptation base if a government mission actually plants one. They will operate it until it is time to come home, and then abandon it, all in the one mission.)

I doubt even Elon Musk will send anything to Mars until either (1) the government pays him to, or (2) the government has found a suitable site and verified ground truth about what resources are really there to use. Which government do I mean? Take your pick. Any or all of them. Doesn't matter. It was like that 500 years ago, too.

As for making ISRU/ISPP work at making propellants, yes I think so, but how good depends upon which one you are really talking about. I think using the Martian atmosphere to make LOX-LCH4 will work, as long as (1) you bring the hydrogen from Earth, or (2) you have an easy source of water at your landing site, and all the means necessary to extract it. I just think it will take years not weeks to accumulate tons of propellant, with any gear we can afford to take there.

If instead you want to use LOX-LH2, your site has to have lots of easy water, or your ISPP cannot work. But solar-powered electrolysis will generate hydrogen and oxygen faster, I think, as long as you can liquify them. Rapid liquifaction is the "long pole" in that tent. In part, because you must store immense volumes of uncompressed gases before running them through the liquifaction plants. "Plants" plural because the equipment to liquify hydrogen gas is quite different from the equipment to liquify oxygen.

Both propellant combinations ultimately require some amount of water. Until we have actual ground truth, we don't know where the water really is, how much there is, what quality it is, or how to transform that which does exist into a usable form. Remote sensing as it exists today cannot answer any of those crucial questions. Neither can zapping surface rocks with a laser, or scratching mere centimeters down with a sampler. You gotta drill 10's to 1000's of meters to find out for sure.

I think I get viewed as a pessimist because I really am an engineer versed in a lot of this stuff. Actually, I am an optimist. But I am also a realist. It's just that everything (in all aspects of life) is always more complicated, and takes longer, than any of us want.

GW

RobertDyck · 2014-01-03 16:27:00

Tom Kalbfus wrote:

From Wikipedia
The Mayflower departed Plymouth, England on September 16, 1620 with 102 passengers and about 30 crew members in the small, 100 foot long ship.
...

Ironic, years ago I posted a design for a passenger module. A module to fit in the Shuttle's cargo hold. This module would be a cylinder, docked to the mid-deck hatch, with 2 decks inside. An airlock at the front, offset to one side, with APAS docking hatch at the top. This would dock to ISS. Beside the airlock would be a ladder between decks. Behind the airlock would be rows of economy class seats: 13 rows, right to the back wall. The upper deck would have space under the seat, and storage compartment above conformant with the curved ceiling; just like an airline economy class seat. The lower deck would have raised seats, no storage compartment above, but a conformant storage compartment below, accessible from the isle at floor level. Life support equipment in bulges below the cylinder, tucked between ribs of the Shuttle's cargo hold.

13 rows, 2 seats each side of the isle, 2 decks = 104 passengers

Flight attendants would sit in the Shuttle itself: 2 on the flight deck behind the pilot and co-pilot, and 3 in the mid-deck. In-flight food storage and prep in the mid-deck. And one toilet in the mid-deck. The airlock is rather big; would there be room beside for a ladder between decks plus a second toilet?

Of course this would only carry passengers to an orbiting station. You would need an orbital hotel for a useful destination. Or an interplanetary transit vehicle to get them to Mars. This wouldn't have any cargo hold, so each passenger would only be permitted clothes he/she wears plus carry-on luggage. Since storage compartments would be exactly the same size and shape as an economy class airliner, it's easy to see how much that is.

Next time you fly, visualize the whole aircraft tilted on its tail, with 5 point seat belt instead of just a lap belt, ready to launch from KSC.

SpaceNut · 2014-01-03 17:28:42

Here is a good post on liquifying gasses.. http://answers.yahoo.com/question/index … 356AABVjc6

here is an old NASA Oxygen Safety Handbook http://www.hq.nasa.gov/office/codeq/doc … 740151.pdf

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