Yet another Mars architecture

kbd512 · 2015-05-09 10:53:00

SpaceNut,

If NASA is serious about humans to Mars, then working within their exiting budget is a top priority. It's highly unlikely that the agency will receive significantly more funding than it already gets. No matter how complex it is perceived to be, orbital assembly built ISS, a far more complicated vehicle than a ITV/MTV from an assembly standpoint, using far lighter payloads and far more expensive launches than what F9H/FH would allow for.

It's not going to cost more to assemble the Mars mission hardware at ISS than it would to fly SLS once or twice per year.

There are three use cases for SLS, all of which accomplish relatively mundane tasks at staggering expense:

1. Launch a MTV, less propulsion, in one flight

If there's no insistence on launching a massive capsule system like Orion with the MTV, then the mass of the MTV remains within the capability of a single F9H flight. Orion wasn't designed for crew sustainment during deep space flights, so there's no point in adding the mass of Orion to the MTV. If the MTV has a problem that makes it uninhabitable in deep space, the result is loss of crew and loss of mission. If the same amount of funding that we've expended to develop Orion was instead spent to develop CL-ECLSS, active radiation shield, and the systems reliability required for deep space transits, we wouldn't need a non-functional lifeboat.

2. Launch a fully fueled multi-person MDV/MAV in one flight

This use case makes the most sense of all the ways in which we could use SLS. Our astronauts need a way to get home, but apart from instant availability, bringing the mass of all the propellant required to get back to Earth from Mars is clearly the most uneconomical way to accomplish this. It can't possibly cost more to develop ISPP for use on Mars than it costs to bring it all from Earth, unless our Mars mission is the type of flags and footprints mission NASA said it didn't want to do.

3. Launch large chemical propulsion stages for orbital transfers

If NASA develops SEP systems for orbital transfer, then there's no logical explanation as to why we'd require the types of kick stages that only SLS could push to LEO. Again, F9H/FH is adequate for smaller chemical kick stages that less massive MTV's and MDV's/MAV's would require in conjunction with SEP.

RobertDyck · 2015-05-09 12:13:28

If you use F9H for everything, that requires splitting the cargo lander and MAV into 2 launches: lander and TMI stage. Again looking at my mission plan, and my plan is strongly based on Mars Direct. But the biggest issue is the hab or ITV (interplanetary transit vehicle). Using artificial gravity, the vehicle is best designed short and fat. A couple days ago I flipped through "The Case for Mars" again, the 1997 edition. In it Robert Zubrin said previous engineers tried to fit the vehicle within the 5 metre fairing of existing launch vehicles, but he argued to fully use the 10 metre width of Ares. Saturn V had a 10 metre diameter first and second stage, initial designs for Ares had an 8 metre core stage based on the Shuttle ET, but the upper stage would be 10 metre. However, final designs for the upper stage had the upper stage 8 metre wide; the same as the core stage. So the final layout for the hab is also 8 metres. But the F9H has a 5 metre fairing. Can it handle an 8 metre diameter payload? That changes aerodynamics. The outer surface of the hab would align with the points of the nose cones of the side boosters. That changes aerodynamic loading. You could launch TransHab in a 5 metre fairing, but that changes the vehicle to soft. How do floors of a soft hab work during artificial gravity? How durable is a soft hab, can it endure long duration storage in space? Remember, I want the ITV to travel from ISS to Mars orbit and back, using aerocapture at both planets. And 12 trips to Mars and back, with planets aligning every 26 months, means 26 years in space. ISS has demonstrated how a hard wall habitat will stand up that long. Unity module (aka Node 1) was attached to Zarya on 6 December 1998. So it's already been 16 years, 5 months, and 3 days.

RobS · 2015-05-09 13:41:13

Only time will tell, but my impression is that inflatables are superior to "tin cans" in many ways. They are multiple layered, they have kevlar armoring built right in, they have multiple airtight layers, they have built in insulating layers, etc. The floors can be made as firm as one wishes; if nothing else, one could install hard plastic panels on them after inflation. Because they don't include metal, they do not produce showers of secondary radiation, and because they are hydrogen-rich they provide better shielding than metal. They can be made quite large but can be carried in a small fairing. If they have an expandable heatshield added to them, they can even have quite a large heat shield but fit in a small fairing. This will require technology development, though.

Alternately, one could create a smaller multi-level hab. The gravity would be higher in the bottom level and lower in each upper level, but that may not be a problem. We know relatively little about artificial gravity, unfortunately.

kbd512 · 2015-05-09 16:57:43

RobertDyck wrote:

If you use F9H for everything, that requires splitting the cargo lander and MAV into 2 launches: lander and TMI stage. Again looking at my mission plan, and my plan is strongly based on Mars Direct. But the biggest issue is the hab or ITV (interplanetary transit vehicle). Using artificial gravity, the vehicle is best designed short and fat. A couple days ago I flipped through "The Case for Mars" again, the 1997 edition. In it Robert Zubrin said previous engineers tried to fit the vehicle within the 5 metre fairing of existing launch vehicles, but he argued to fully use the 10 metre width of Ares. Saturn V had a 10 metre diameter first and second stage, initial designs for Ares had an 8 metre core stage based on the Shuttle ET, but the upper stage would be 10 metre. However, final designs for the upper stage had the upper stage 8 metre wide; the same as the core stage. So the final layout for the hab is also 8 metres. But the F9H has a 5 metre fairing. Can it handle an 8 metre diameter payload? That changes aerodynamics. The outer surface of the hab would align with the points of the nose cones of the side boosters. That changes aerodynamic loading. You could launch TransHab in a 5 metre fairing, but that changes the vehicle to soft. How do floors of a soft hab work during artificial gravity? How durable is a soft hab, can it endure long duration storage in space? Remember, I want the ITV to travel from ISS to Mars orbit and back, using aerocapture at both planets. And 12 trips to Mars and back, with planets aligning every 26 months, means 26 years in space. ISS has demonstrated how a hard wall habitat will stand up that long. Unity module (aka Node 1) was attached to Zarya on 6 December 1998. So it's already been 16 years, 5 months, and 3 days.

Rob,

I'm not concerned with splitting a launch into a payload and propulsion segment or providing artificial gravity, as useful as that would be for long duration missions. I provided a potential MTV design that incorporates artificial gravity and permits SEP to be incorporated into the vehicle, but it requires assembly at ISS, a larger payload fairing for F9H/FH, and/or SLS because it uses a Skylab II primary module, an artificial gravity module, and an ISS module as a secondary module.

NASA has elected to use ISS hardware for their deep space habitat. ISS hardware is more than capable of long duration operation in space. ISS modules don't require basic testing in space. That's already been done. Inflatable modules still require some more testing in space, but that technology is also proven to work. I really don't care what combination of soft and hard modules NASA decides to use, so long as the MTV has a primary and backup habitation module capable of sustaining the astronauts for the entire mission duration. There are any number of configurations that would work. I just want NASA to pick one and develop the concept into a ITV/MTV.

As far as LEO assembly at ISS is concerned, we can afford to do that at least five times with F9H/FH before we approach the cost a single SLS flight. NASA has also elected to use SEP hardware for deep space propulsion. That dramatically increases the mass that can be pushed to Mars. The cargo doesn't have to get there fast, it just has to get there.

For the cargo mission components, use SEP + aerocapture + ADEPT.

If an aerocapture goes wrong, nobody dies.

For the crewed mission components, use combined chemical/SEP + propulsive capture + HIAD.

The risks and thermal protection mass increases required for aerocapture aren't worth the minor dV hit. We use kick stages to push the MTV to Mars from L1, SEP to spiral into LMO, chemical or SEP to transfer to L1 from LMO, and SEP to capture at L1. This avoids the radiation issues from manning the MTV while it traverses the Van Allen belts.

After an initial effort to put the MTV into orbit and a mobile mission architecture on Mars, there's no reason why we can't just send spare parts to refurbish vehicles.

RobertDyck · 2015-05-09 17:30:07

SEP makes a lot of sense for cargo. It's very efficient, but slow. If you read "Mars Direct", Dr. Zubrin himself started by arguing for nuclear thermal propulsion. His partner argued that nuclear would incur additional political obstacles, so why? LOX/LH2 is enough to send a human mission.

You mention L1. Why? It doesn't have any benefit. Just send a cargo from ISS directly, an unmanned vehicle using SEP can spiral out of Earth orbit, use gravity assist from the Moon, then proceed directly on to Mars. The Moon doesn't provide much gravity assist, but every little bit helps.

If your manned mission requires any sort of assembly or rendezvous beyond ISS, it's bad.

Cargo: SEP + direct entry + ADEPT
Crew: chemical + aerocapture + ADEPT

My understanding is HIAD can handle small/light cargo, but would have difficulty with high speed (high energy) or heavy cargo. Once you expand a crew entry vehicle from one person to the entire surface habitat, it's too big for HIAD. Then it becomes a job for ADEPT.

Interesting. These web pages (news and game) talk about using HIAD + parachute to return a Cygnus cargo craft to Earth from ISS. It works well enough for Earth?

kbd512 · 2015-05-09 18:17:06

RobertDyck wrote:

SEP makes a lot of sense for cargo. It's very efficient, but slow. If you read "Mars Direct", Dr. Zubrin himself started by arguing for nuclear thermal propulsion. His partner argued that nuclear would incur additional political obstacles, so why? LOX/LH2 is enough to send a human mission.

We're not going to get NTR's. That technology is gone. We already have chemical and we're going to have SEP. Between a high efficiency propulsion system that permits sending more massive payloads to Mars and a low efficiency propulsion system that severely limits payload mass, I know which one I'd choose. NASA made the same choice.

RobertDyck wrote:

You mention L1. Why? It doesn't have any benefit. Just send a cargo from ISS directly, an unmanned vehicle using SEP can spiral out of Earth orbit, use gravity assist from the Moon, then proceed directly on to Mars. The Moon doesn't provide much gravity assist, but every little bit helps.

The benefit to launching the crew to the MTV at L1 and transfer of the MTV to L1 is an unmanned traverse of the Van Allen belts using the MTV's onboard SEP, systems testing that doesn't endanger a crew, and lower dV requirements for an impulsive transfer to Mars.

RobertDyck wrote:

If your manned mission requires any sort of assembly or rendezvous beyond ISS, it's bad.

My mission architecture requires no assembly or rendezvous at Mars, although I see no issue with using a chemical kick stage at Mars. I use individual astronaut transfer from LMO to the surface of Mars and from the surface of Mars to LMO because a single F9H/FH flight can land a single person MDV/MAV and it permits testing and staging multiple MDV and MAV vehicles on Mars. In other words, I prefer a thorough test program and backups so that an event that renders a particular vehicle inoperable doesn't strand the entire crew on Mars.

RobertDyck wrote:

Cargo: SEP + direct entry + ADEPT
Crew: chemical + aerocapture + ADEPT
My understanding is HIAD can handle small/light cargo, but would have difficulty with high speed (high energy) or heavy cargo. Once you expand a crew entry vehicle from one person to the entire surface habitat, it's too big for HIAD. Then it becomes a job for ADEPT.
Interesting. These web pages (news and game) talk about using HIAD + parachute to return a Cygnus cargo craft to Earth from ISS. It works well enough for Earth?

Regarding the cargo, I meant direct entry.

Yes, HIAD can provide braking for a small MDV of the type I had in mind. In fact, it's already handled braking for a vehicle in the mass range that I had in mind. Landing MTVL sized payloads on Mars requires F9H/FH, a relatively modest SEP tug already in development for ARM, and ADEPT for EDL.

I wanted to use M113's/MTVL's on Mars because the vehicles are durable enough and shielded well enough to permit continuous mobile surface operations over the course of a three mission campaign by providing spare parts for subsequent missions. I don't want to establish a base and then never leave the base. Going to Mars is supposed to be about answering fundamental questions and determining where the best locations are for a permanent human presence. That'll only happen if our surface mission hardware is designed for mobile operations.

The bottom line is that using F9H/FH where feasible, using SLS only when absolutely required, and killing the Orion program means money for systems development, testing on Mars (the best lab available for determining how hardware will perform on Mars), and decades not lost to impractically expensive solutions.

RobertDyck · 2015-05-09 20:43:47

kbd512 wrote:

We're not going to get NTR's.

You keep talking about advanced propulsion. We can go to Mars using the upper stage of SLS. Or LH2/LOX upper stage of any heavy lift launch vehicle. We don't need advanced propulsion. Of advanced propulsion systems available, NTR is the most developed and best performance. STOP TALKING ABOUT SEP FOR CREW!!!

Here is what SEP for crew looks like. This is the Russian mission plan...

Sequence: 3 months spiral out of Earth orbit, 8 month transit to Mars, 1 month spiral down to Mars working orbit, 1 month on the surface of Mars, 1 month spiral out of Mars orbit, 7 month transit back to Earth, 3 month spiral down to LEO.

And that's a lot better than I expected. It requires high power SEP to achieve that. Deep Space One took a lot longer to reach an asteroid as far as Mars. But look what this does: only 1 month on Mars. And extended duration in space. Any effective mission architecture gets crew to the surface of Mars fast! Protection from radiation, micrometeoroids, and gravity.

kbd512 wrote:

RobertDyck wrote:
If your manned mission requires any sort of assembly or rendezvous beyond ISS, it's bad.
My mission architecture requires no assembly or rendezvous at Mars

That's not what I said and you know it. First, Mars orbit rendezvous is not a problem. But your mission architecture requires assembly in LEO, then launch without crew, then a crew vehicle has to catch up months after launch. That doesn't just deliver crew, it attaches a crew capsule. That second assembly will not be at ISS, with all the infrastructure of ISS. It's in deep space. Not good.

kbd512 wrote:

Going to Mars is supposed to be about answering fundamental questions and determining where the best locations are for a permanent human presence.

No, going to Mars is about *ESTABLISHING* a permanent human presence. Not spending billions of dollars to just think about it. To quote the running shoe commercial: "Just do it."

Last edited by RobertDyck (2015-05-10 10:40:35)

kbd512 · 2015-05-09 22:23:18

RobertDyck wrote:

You keep talking about advanced propulsion. We can go to Mars using the upper stage of SLS. Or LH2/LOX upper stage of any heavy lift launch vehicle. We don't need advanced propulsion. Of advanced propulsion systems available, NTR is the most developed and best performance. STOP TALKING ABOUT SEP FOR CREW!!!

Rob,

I've learned that everyone is terrified of anything with the "N" word in it.

I want to use a SEP tug to position the MTV at L1 after assembly at ISS.

I want to use Dragon V2 and F9H/FH to quickly transfer the crew to the MTV at L1. The SEP tug that delivered the MTV to L1 will take the Dragon capsule back to ISS for use by the an ISS crew.

I want to use a chemical kick stage attached to the MTV to depart L1.

I want to use SEP so that the MTV can spiral in to LMO.

I want to use SEP to depart LMO for L1. Alternatively, a SEP tug could attach a chemical kick stage to the MTV at Mars.

I want to use micro capsules to individually transport the crew to the surface and have the MTVL's retrieve them after landing.

I want to use SEP to spiral in to L1.

I want to use another Dragon V2 and F9H/FH to quickly transfer the crew from the MTV at L1 to ISS or simply return them to Earth.

I want to use a SEP tug to take the MTV back to ISS for refurbishment and resupply.

RobertDyck wrote:

Here is what SEP for crew looks like. This is the Russian mission plan…
Sequence: 3 months spiral out of Earth orbit, 8 month transit to Mars, 1 month spiral down to Mars working orbit, 1 month on the surface of Mars, 1 month spiral out of Mars orbit, 7 month transit back to Earth, 3 month spiral down to LEO.

Russia's plan is to use SEP for everything. I don't want to do that. My plan shaves a good 7 months off Russia's plan.

RobertDyck wrote:

And that's a lot better than I expected. It requires high power SEP to achieve that. Deep Space One took a lot longer to reach an asteroid as far as Mars. But look what this does: only 1 month on Mars. And extended duration in space. Any effective mission architecture gets crew to the surface of Mars fast! Protection from radiation, micrometeoroids, and gravity.

My architecture gets the crew to Mars in about 7 months and returns to L1 in about 7 months. Losing a couple months of exploration time to a much less dangerous orbital insertion method that has lower technology development and mass requirements is not the end of the world.

RobertDyck wrote:

That's not what I said and you know it. First, Mars orbit rendezvous is not a problem. But your mission architecture requires assembly in LEO, then launch without crew, then a crew vehicle has to catch up months after launch. That doesn't just deliver crew, it attaches a crew capsule. That second assembly will not be at ISS, with all the infrastructure of ISS. It's in deep space. Not good.

Yes, Rob, the crew does have to be sent to L1 to get to the MTV and depart L1 for LEO. The capsule doesn't stay attached to the MTV, it's returned by the SEP tug that transferred the MTV to L1. Obviously the mechanics of docking work a bit differently at L1 than in LEO or LLO or LMO. It's still not a major problem.

RobertDyck wrote:

No, going to Mars is about *ESTABLISHING* a permanent human presence. Not spending billions of dollars to just think about it. To quote the running show commercial: "Just do it."

If we don't find life on Mars, I would like to keep searching. If Mars doesn't have microorganisms in the subsurface water, I want to determine whether or not Titan or Europa have life. Are we alone in the universe or are we part of a greater general phenomenon?

Establishment of a human presence on Mars isn't about exploration, it's about colonization. Should we colonize Mars? I think so, but there has to be broad public support for that endeavor that doesn't currently exist. Exploration doesn't require much explanation. We're naturally curious. Eventually, I think Mars will be Earth 2 and Titan Earth 3. Those are far future goals. That said, let's have a look around our solar system with our own eyes, as much of it as we can reasonably explore, and see what we can find.

RobertDyck · 2015-05-09 22:51:06

Mars One doesn't have an effective plan to get to Mars. And any application that didn't have a $100 donation (or larger) was ignored. How many applications did they get? The owner said over 100,000. Work that out, at $100 per application, he got how much money? For a plan that has no way to get back to Earth. I would say there is public support. The public is just tired of hearing talk with no action. Once you start delivering results, see how that changes.

RobS · 2015-05-10 08:47:09

The problem I have with solar electric propulsion isn't the idea, but the propellant. Xenon costs $120 per 100 grams. That's $1,200 per kilogram and $1.2 million per tonne. Once Space X gets launch costs down below $1,000 per kilogram, it'll become less competitive or uncompetitive, especially when one considers the cost of developing and building the SEP vehicles. Currently, world production is not high enough to produce many tonnes of the stuff, either, without raising the production price quite a bit.

A switch to argon fixes that problem, but requires more electrical power, since argon is harder to ionize per kilogram.

SpaceNut · 2015-05-10 08:48:17

A human mission to anywhere that involves more than a few days stay is not exploration in the truest sense as we have put up roots even if you think they are temporary which is a settlement. Only a robotic mission is exploration as there is no habitat, food or water required...

Antius · 2015-05-11 04:54:09

kbd512 wrote:

RobertDyck wrote:
You keep talking about advanced propulsion. We can go to Mars using the upper stage of SLS. Or LH2/LOX upper stage of any heavy lift launch vehicle. We don't need advanced propulsion. Of advanced propulsion systems available, NTR is the most developed and best performance. STOP TALKING ABOUT SEP FOR CREW!!!
Rob,
I've learned that everyone is terrified of anything with the "N" word in it.
I want to use a SEP tug to position the MTV at L1 after assembly at ISS.
I want to use Dragon V2 and F9H/FH to quickly transfer the crew to the MTV at L1. The SEP tug that delivered the MTV to L1 will take the Dragon capsule back to ISS for use by the an ISS crew.
I want to use a chemical kick stage attached to the MTV to depart L1.
I want to use SEP so that the MTV can spiral in to LMO.
I want to use SEP to depart LMO for L1. Alternatively, a SEP tug could attach a chemical kick stage to the MTV at Mars.
I want to use micro capsules to individually transport the crew to the surface and have the MTVL's retrieve them after landing.
I want to use SEP to spiral in to L1.
I want to use another Dragon V2 and F9H/FH to quickly transfer the crew from the MTV at L1 to ISS or simply return them to Earth.
I want to use a SEP tug to take the MTV back to ISS for refurbishment and resupply.
RobertDyck wrote:
Here is what SEP for crew looks like. This is the Russian mission plan…
Sequence: 3 months spiral out of Earth orbit, 8 month transit to Mars, 1 month spiral down to Mars working orbit, 1 month on the surface of Mars, 1 month spiral out of Mars orbit, 7 month transit back to Earth, 3 month spiral down to LEO.
Russia's plan is to use SEP for everything. I don't want to do that. My plan shaves a good 7 months off Russia's plan.
RobertDyck wrote:
And that's a lot better than I expected. It requires high power SEP to achieve that. Deep Space One took a lot longer to reach an asteroid as far as Mars. But look what this does: only 1 month on Mars. And extended duration in space. Any effective mission architecture gets crew to the surface of Mars fast! Protection from radiation, micrometeoroids, and gravity.
My architecture gets the crew to Mars in about 7 months and returns to L1 in about 7 months. Losing a couple months of exploration time to a much less dangerous orbital insertion method that has lower technology development and mass requirements is not the end of the world.
RobertDyck wrote:
That's not what I said and you know it. First, Mars orbit rendezvous is not a problem. But your mission architecture requires assembly in LEO, then launch without crew, then a crew vehicle has to catch up months after launch. That doesn't just deliver crew, it attaches a crew capsule. That second assembly will not be at ISS, with all the infrastructure of ISS. It's in deep space. Not good.
Yes, Rob, the crew does have to be sent to L1 to get to the MTV and depart L1 for LEO. The capsule doesn't stay attached to the MTV, it's returned by the SEP tug that transferred the MTV to L1. Obviously the mechanics of docking work a bit differently at L1 than in LEO or LLO or LMO. It's still not a major problem.
RobertDyck wrote:
No, going to Mars is about *ESTABLISHING* a permanent human presence. Not spending billions of dollars to just think about it. To quote the running show commercial: "Just do it."
If we don't find life on Mars, I would like to keep searching. If Mars doesn't have microorganisms in the subsurface water, I want to determine whether or not Titan or Europa have life. Are we alone in the universe or are we part of a greater general phenomenon?
Establishment of a human presence on Mars isn't about exploration, it's about colonization. Should we colonize Mars? I think so, but there has to be broad public support for that endeavor that doesn't currently exist. Exploration doesn't require much explanation. We're naturally curious. Eventually, I think Mars will be Earth 2 and Titan Earth 3. Those are far future goals. That said, let's have a look around our solar system with our own eyes, as much of it as we can reasonably explore, and see what we can find.

Why not use SEP to get the hab and lander to Mars orbit (unmanned) and chemical propulsion for the transfer vehicle? A pure human transfer vehicle could be low mass. It doesn't need to carry anything other than an aerobrake and the food that the crew will consume getting there and getting back. The propellant can be used to provide cosmic ray shielding.

If the EM drive is able to produce the thrust levels that Chinese experiments indicate, then both convention SEP and chemical propulsion will be obsolete.

RobertDyck · 2015-05-11 06:39:17

Also realize how big solar arrays have to be. The Russian plan would use a single station module, based on their Zvezda. That's the one NASA calls the Russian service module, with living quarters and life support. Look how big the solar arrays are. And their plan uses thin film photovoltaic panels.

Compare that to American solar arrays on ISS

Wikipedia wrote:

Each of the Solar Array Wings are 34 m (112 ft) long by 12 m (39 ft) wide, and are capable of generating nearly 32.8 kW of DC power. They are split into two photovoltaic blankets, with the deployment mast in between. Each blanket has 16,400 silicon photovoltaic cells, each cell measuring 8 cm x 8 cm, grouped into 82 active panels, each consisting of 200 cells, with 4,100 diodes.
Each pair of blankets is folded like an accordion for compact delivery to space. Once in orbit, the deployment mast between each pair of blankets unfolds the array to its full length.

Generating 15MW would require 457.3 wings. So if you think American solar arrays would be smaller, dream on. This Russia plan is a few years old, do you want to re-calculate solar array size using the latest cells from SpectroLab?

GW Johnson · 2015-05-11 13:39:07

Electric propulsion to spiral out and in slowly is an old idea dating to the mid-1950's. They just didn't have the technology to do it then. Also back then, they assumed nuclear power would run the thrusters. Today, solar looks better until you get out near the Main Belt. Reactors as electricity generators turned out to be a lot heavier than was generally thought back then, even though we were sticking our first atomic steam turbine plant inside a submarine hull about that time.

You use electric thrusters during transits as well, to shorten them, accelerating to mid, the decelerating the other half to enter your spiral-in. Again, first proposed in the 1950's, although back then, they did not yet know about the Van Allen radiation belts. With mere Newtons of thrust from 100's to 1000's of kg of hardware, not to mention the ship structure mass, spirals take months. No help for that.

That being said, electric is perfectly fine for sending unmanned things. For men you have two options. First, add impulsive burns to depart and arrive, and just use SEP during the transits (eliminate the spirals). Or, second, use something about like a manned moon rocket to send the crew when the spiral-out is nearly completed as an unmanned item. No radiation belts at Mars, you can spiral-in with men, if you can afford the time and life support mass.

Besides the time (and associated life support mass), you have to avoid long exposure of the crew to the Van Allen belts. Either approach will work, and by the time you send a crewed moon rocket, I'd bet even the costs are comparable. The only difference is time in confinement for the crew. The longer, the bigger the habitat space you must throw. No way around that, either.

I'd be careful about designing to the best marketing data from any given solar cell manufacturer. That kind of stuff rarely has the "fine print" in it. And that "fine print" is what kills a lot of otherwise-good designs. Do your design with more-middle-of-the-road stuff, and if your components end up beating that level of performance, then so much the better.

I know little about electric thrusters. I do know there's more than one kind. Some are already flying in space pushing probes around and satellites, too. Is xenon the only propellant we actually have working? Or could we use something a little more common. This ionization thresh-hold thing, is that dependent upon power, or is it more a voltage thing? I honestly don't know. But if its voltage, you can have a lot of that from a big array. Which you'll have anyway.

Artificial gravity-by-spin: there are two stable configurations. One is short but broad, in the limit a discus shape. The other is long and narrow, spinning head-over-heels like a baton. The real trick is to get the shape without introducing extra inert mass. Use what you have to have anyway, to achieve your shape. I like the baton better, it's easy to dock cylindrical modules of propellants together into such a shape. 4 rpm at 56 m radius = 1 full Earth gee. Even civilians off the street can acclimatize "quickly" (days) to 3-4 rpm.

GW

PS -- I'd go with 1 full gee because we have no direct data to suggest anything less is therapeutic enough. Especially if a free-return home is involved, the crew must be fully fit to survive the entry at greater-than-escape speed. It'll be 10-15 gees, at least. It was 11 gees coming home from the moon, right at escape speed. Whatever you do, however you do it, you must provide close to 1 gee for full fitness, because of that free return situation, even if it's a bail-out mode you really didn't intend as "primary".

Last edited by GW Johnson (2015-05-11 13:43:31)

SpaceNut · 2015-05-11 18:29:33

Here is a thought send up 6 ISS modules and 3 interconnecting nodes and make it into a double HH with the center being the connections for the EDS fuel and the Mars lander to make up the Mars Transit vehicle being set such as to make the arms odules into a square circle once spinning. The passage ways from the arms back to the ccore would be for storage and access into the Mars Lander. The Earth return capsule can be staged via SEP either in Mars orbit but would be better in Earth orbit to mate up with the Transit vehicle.

kbd512 · 2015-05-11 19:33:57

Antius wrote:

Why not use SEP to get the hab and lander to Mars orbit (unmanned) and chemical propulsion for the transfer vehicle? A pure human transfer vehicle could be low mass. It doesn't need to carry anything other than an aerobrake and the food that the crew will consume getting there and getting back. The propellant can be used to provide cosmic ray shielding.

We're using chemical propulsion to push the MTV from L1 to Mars to shorten transfer time. The use of SEP to spiral into LMO is driven by three factors.

First, we want to keep the MTV mass within the capability of two to three F9H/FH flights to ISS.

Second, we need to work within current budgets with respect to launch and operating costs.

Third, forgoing development of massive capsules, massive landers, massive habitation modules, and the massive propulsion systems required to move the aforementioned mission hardware components around leaves funding available for development of technology areas that we're still weak in, like closed loop ECLSS, active radiation shielding, communications, etc.

I would like to send multiple small mobile habitation modules ahead of the crew as part of a mobile surface exploration architecture. In the military, if you want to ensure that you have a specific item or tool in working condition, you bring two or more with you. I feel the same way about the surface exploration hardware. As others have previously noted, even the surface of Mars is a completely unforgiving operating environment. Therefore, bring at least two of everything you need.

Every NASA proposal I've seen involves connecting a large capsule system, the MDV, the MTV, and the propulsion system together. The total mass of these systems is well over 100t. It makes a lot of sense from an operations standpoint until you review the propulsion system requirements. Then the IMLEO requirements start looking like science fiction in terms of actual NASA budgets.

I dislike the idea of aerobraking into a highly variable atmosphere. It's not impossible, but there are several challenges with development of a working implementation suitable for human use. The most specific problem I can think of is the thermal protection requirements for such a vehicle. If you mis-calculate, the result should be pretty obvious.

With respect to use of reaction mass for shielding, what do you use for shielding when the reaction mass is gone? I think an active shielding device combined with a water tank, required for any manned mission irrespective of what other technology is available, is the best solution to the problem.

Antius wrote:

If the EM drive is able to produce the thrust levels that Chinese experiments indicate, then both convention SEP and chemical propulsion will be obsolete.

Even if EM drive turns out to be a completely usable form of in-space propulsion, which is unknown at this point, my guess is that such devices will have similar power requirements to SEP and similar thrust levels. Doing away with the requirement to store and ionize an expensive reaction mass like Xenon would still be a major score, though.

Last edited by kbd512 (2015-05-11 20:00:55)

kbd512 · 2015-05-11 20:17:49

SpaceNut wrote:

Here is a thought send up 6 ISS modules and 3 interconnecting nodes and make it into a double HH with the center being the connections for the EDS fuel and the Mars lander to make up the Mars Transit vehicle being set such as to make the arms odules into a square circle once spinning. The passage ways from the arms back to the ccore would be for storage and access into the Mars Lander. The Earth return capsule can be staged via SEP either in Mars orbit but would be better in Earth orbit to mate up with the Transit vehicle.

If we're going to send that much hardware up to assemble a MTV, why not assemble two MTV's, thereby providing redundancy, and fly them to Mars in loose formation to provide mutual assistance in the event that one of the MTV's becomes uninhabitable?

Each MTV would consist of the following:

1 ISS lab module for habitation, flight control, and work/rec space

1 Node module to attach inflatable modules to and for EVA

2 to 4 BEAM's for consumables and spares storage

1 SEP module to spiral in to LMO and to spiral in to L1

A few additional thoughts:

Send the EDS to Mars as cargo using a SEP tug

Mate the EDS to the MTV at Mars for return

SpaceNut · 2015-05-11 20:40:39

EDS is Earth departure Stage but sending the fuel to Mars is not the problem as it is the boiloff for cryogenic fuels that is the issue for being staged in Mars orbit. Active cooling would be a necessity for these to be not an issue, with the only trouble is the power source and radiators to vent the heat to space.

kbd512 · 2015-05-11 21:56:12

SpaceNut,

Oops, I thought you wanted to use EDS and the ZBO tech NASA is working on to return your MTV to Earth (an all-chemical mission).

RobS · 2015-05-12 18:27:53

Musk has said that with the Falcon Heavy, the Dragon 2 can be used to land 2 to 4 tonnes payload on Mars:

http://www.nasaspaceflight.com/2015/05/ … -explorer/

He also says by removing the parachutes and heat shield and increasing the propellant load, it could land on the moon or even Europa.

GW Johnson · 2015-05-27 09:20:05

I see on the internet news early reports of the results of a 91 day study of mice on ISS, the so-called "astro-mice". 3 of only 6 died, so the statistics are questionable at best. But, results suggest that 3 months zero gee causes thinning and loss of elasticity in the skin, plus some sort of hair growth abnormalities. It does suggest why astronauts on MIR complained about itchy, easily-damaged skin.

OK, so add skin damage to bone loss, weakened heart, immune system degradation, and vision damage. These are the side effects of extended exposure to weightlessness, on a time scale of 3-6 months.

Is it not about time for NASA and all the rest of us to "belly up to the bar" and make spin "gravity" an integral part of any manned mission design to Mars? Don't we know enough now, to know that we have to do this to keep the crew healthy? The one-way transit time is longer than 90 days, after all, with any imaginable combination of known propulsion.

And, we as-yet do not know if 0.38 gee at Mars is enough to help stave off these microgravity health effects. So, if we base from LMO for at least part of the mission, I'd spin the ship while parked there. Although, chances are, 0.38 gee will help. How much it helps is what we still don't know. But, we still have about 10 years to find out, before any expedition plan gets "frozen".

Besides, spin "gravity" makes all sorts of life support easier to accomplish. Water, wastewater, cooking. All those get easier.

Add to this picture the fact that tight confinement degrades sanity (ask anyone who ever served time in solitary in a small cell. No crew is going to survive-sane the round trip to Mars riding in tight space capsules or small habitat modules. The vehicle must have lots of room, with its distribution and function guided by psychology as much as anything else.

No successful vehicle design is going to be small enough to launch on one rocket, SLS or otherwise. We're looking at assembly in LEO of something largish, because of these two issues. Is it not time to face up to that?

Not the size of ISS (that came from folks trying to kill the idea of going to Mars), but maybe about an old-time Skylab volume for each group of 3 or 4 people. They'll need it both ways.

GW

RobS · 2015-05-27 09:30:12

I agree, GW Johnson! I suspect on Mars, adding weights to clothing will also help the cardiovascular system and the bones, but we need research, and a spinning module in LEO is the way to do it. It will be easy to do, too, in five years, with Bigelow inflatables and the Falcon Heavy as a launch vehicle.

As for a large volume, it need not add a lot of mass. Some of the volume needs to be armored and robust, but some of it--think a gym module--could be a fairly simple inflatable. But it does need to be repairable.

RobertDyck · 2015-05-27 15:22:04

Ok. GW, would you be willing to work with me to flesh-out the mission plan that I laid out? The one in this discussion thread.

My mission plan started with Mars Direct, but I tried to tweek it. One issue I had was that Mars Direct goes to great lengths to reduce total mass launched from Earth, but the Earth return capsule is dropped onto the surface of Mars just to lift it off again. So one point is to leave the Earth return vehicle parked in Mars orbit. Mars Semi-Direct did that, but had the problem of bringing return fuel from Earth. I want to use ISPP for all return fuel. I have a concern that any Mars mission will only be flags-and-footprints, so to ensure a sustained Mars program the interplanetary vehicle is reusable. That also reduces the cost for the second and subsequent missions.

A couple interesting points about Mars Direct. The initial version shown in slides published on the old Mars Direct website showed a hab with one deck only. Floor plans showed only one deck, but the side view in the slides only included that one deck. Beneath was landing rockets, fuel tanks, and an enclosed space that presumably would house life support. Apollo housed life support in the service module, inaccessible by crew; apparently the first version of the Mars Direct hab did too. ISS has demonstrated crew need access for maintenance & repair. There was mass allocation for a rover, but no garage. I can only assume the rover was to be suspended beneath by cables, similar to the skycrane of Curiosity. This was later changed to a lower deck, but we have to be very wary of mass creep. Most spacecraft designs start lean, then get all sorts of things added to them that dramatically increase mass. Looks like the Mars Direct hab is victim of this too. MDRS and FMARS make full use of the lower deck, even though that space would fully consumed by the vehicle garage, fuel tanks for landing, and life support equipment. Any space around the vehicle would be packed with surface science equipment, and the inflatable greenhouse. Think of a single car garage with a car in it, with yard tools stuff just packed around the car.

I would still like to assume use of SLS. Congress is looking for an excuse to justify its decision to build it. So what I'm proposing is a reusable vehicle to go from ISS to Mars orbit and back. Base on the Mars Direct hab, but only one floor. The airlock would have a ladder up and down. Below would be a single Dragon spacecraft; this is what SciFi calls an emergency escape pod, or the Navy calls a life boat. In case aerocapture fails. Beneath that an ADEPT heat shield. Above would be attached the Mars lander. This whole thing would be attached to a cable for artificial gravity, using the spent TMI stage a counterweight. Just like Mars Direct. On return to Earth, the spent TEI stage would be the counterweight.

Mars Direct from the March 2000 issue of Scientific American. I could give a larger line drawing.

And Mars Direct tether:
71511-img3

Next is what should we use for the lander? All inflatable, with just a seat for each astronaut during landing? Or a hard wall hab? I have suggested making food and supplies of the lander accessible in case free return is necessary. Do we dock the lander up-side-down on the roof the ITV? That's fine if you don't plan on entering until Mars orbit, because the tether will be cut before aerocapture, so enter in zero-G. If it's hard wall, then people would expect to use that space during transit. The lander would have its own heat shield for atmospheric entry. You can dock the lander to the ITV roof-to-roof, so the heat shields are not pierced, but that means the lander will be up-side-down during transit.

I proposed pre-landing the Mars Ascent Vehicle, and using the MAV as the TEI stage. That allows ISPP for all return propellant. The MAV would not require a pressurized cabin, just a fairing. Astronauts in spacesuits, dock to the ITV within hours. They can dock to ISS now in hours. How long did Apollo LM take: launch from the Moon to dock with CSM? Expect the Mars vehicle to do it just as quick.

Should we pre-land the Mars surface hab? I suggested the that be included with the crew lander. Should the crew land with nothing but a capsule? If we do send a large lander, and if every mission goes to the same location, we will build up the base with each mission. And there's safety of landing with the surface hab.

Yes, I am proposing we do it. Don't whine that NASA must do it, because either they won't or they won't do it your way. If you want it done right, do it yourself.

RobS · 2015-05-27 18:25:38

Robert, one thing to consider, where the flags and footprints issue is concerned, is designing one basic lander than can carry either humans or cargo to the surface. You will need cargo landers. A Falcon Heavy can send 14 tonnes to TMI and 11 tonnes to the surface (and Zubrin was assuming a hydrogen-oxygen TMI stage). The SLS, with 30% more payload to orbit, should be able to send 30% more to TMI; that's 18 tonnes, and 14 tonnes to the Martian surface. Assuming heat shield, engines, and landing legs are 25% of that, that's 10 tonnes of cargo on the surface for SLS and 8 tonnes for Falcon Heavy. (I am not sure 25% is right; it's my guess.) If you want to double that by using two launches, that's 20 tonnes cargo to the surface for SLS and 16 for Falcon Heavy.

I would start with numbers like that. The vehicle carrying people down should be either 11 tonnes in Mars orbit before descent (Falcon Heavy) or 14 tonnes (SLS) or double that. If it were double that, you could land your crew with plenty of supplies, an inflatable greenhouse, etc. The MAV could be double those numbers as well, which is plenty for some additional cargo, plus solar power or nuclear power for ISRU and hydrogen or methane. Once you figure those things out, you can figure out whether you can accommodate a hard sided cabin or not.

RobertDyck · 2015-05-27 20:56:52

That doesn't make sense. SLS Block 2 (the only version of SLS worth anything) can lift 130t to LEO. Falcon 9 Heavy (now called Falcon Heavy) can lift 58t to LEO. How could SLS throw 18t to TMI, and F9H throw 14t?

I have figures for Energia. It could lift 88 metric tonnes to 200km orbit at 51.6° inclination. That's without it's upper stage, demonstrated by Polyus. With EUS it could throw 35,680kg to C3=0, 31,091kg to C3=10, 17,446 to C3=50, or 8,006 to C3=100. These figures are from a NASA web page for international launch vehicles. Robert Zubrin used C3=15 for TMI. Interpolating that works out to about 28.5t to TMI. It's not linear so I used a weighted average of interpolation from the lower and higher figures.

The ratio doesn't perfectly apply to American rockets, because American rockets are rated to 185km orbit from KSC or Cape Canaveral Air Force Station. The ratio appears to show your figure for TMI for F9H is correct. However, SLS Block 2 should be much higher. Are you assuming SLS Block 1, with only 70t to LEO?

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