Yet another Mars architecture

RobertDyck · 2014-03-29 00:54:47

Quaoar wrote:

Another solution may be to use an enflatable tank inside an empty space: when the propellant is burned, astronauts throw away the tank and mount the forniture.

This means a tank liner (bladder) during launch. Throw away the liner after the module is in space. That means any RP-1 contamination is thrown away with the liner. The issue with this is interior walls and furniture cannot be attached during launch.

Quaoar · 2014-03-29 04:42:30

RobertDyck wrote:

This means a tank liner (bladder) during launch. Throw away the liner after the module is in space. That means any RP-1 contamination is thrown away with the liner. The issue with this is interior walls and furniture cannot be attached during launch.

Yes: astronauts have some kind of habitat assembly kit, and mount it after trow away the empty bladder.

Last edited by Quaoar (2014-03-29 04:43:58)

SpaceNut · 2014-04-04 20:12:38

I guess the question then is how much stuff would we need to have a successful ship for a long spanning timeframe as well as journey transported up to the parked location for the purpose of reuse of the spent fuel stage..by another ship.

GW Johnson · 2014-04-05 09:34:09

This might be off-the-wall, but it seems to me that converting a propellant tank to habitable space involves a lot of effort and maybe significant hardware weight that could be avoided by using a different approach.

Why not just build the habitable spaces as dedicated modules, and then dock propellant tanks and propulsion items to it, in space. All of these may then be "optimized" for their roles, especially if you want to re-use this vehicle for multiple missions. The only things needing replacement are the life support consumables and the propellants, and periodically for maintenance, the engines.

Propellant replenishment could either be by swapping modules (an un-dock and re-dock process), or by direct propellant transfer (the rudiments of which have been established at ISS). Life support replenishment is just moving packaged cargo from one vehicle to another, as is done now at ISS.

If you consider the modules of the vehicle you are trying to build to be payloads-only on the rockets that launch them, then you divorce the two designs. Your modules need not attempt to serve as their own launch propulsion, so that those requirements do not compromise their design.

The commercial rockets we already have can launch payloads to LEO in the 10-25 ton class, depending upon launcher configuration. These are commercial satellite launch rockets whose design has been simplified enough, and (more importantly) whose support logistics have been reduced enough, to be considered business-competitive at around $5000/kg or so. Supposedly, Falcon-Heavy should fly this year, offering 53-ton capability at something like $2300/kg.

All of these have standard-sized payload shrouds not much smaller than the old Shuttle bay. There is no reason some of our contemplated modules could not ride "naked" on the launch rocket, dispensing with payload shrouds altogether. For that last, wind blast and ascent heating must be taken into account, but that's nowhere near as severe as re-entry. You just need to stay within the demonstrated "hammerhead" design limits on diameter.

The downside to this is only that you must launch to LEO and dock your stuff there. It sort-of rules out "direct" missions. But the upside is that it uses the cheapest launchers available: the commercial ones. (I fear SLS will never be cheap. No government design ever has been.) If we are talking about reusable vehicles, then orbital basing is exactly what we want. With reuse, you get to "amortize" the costs of building and replenishing this thing over the several missions that it flies.

Remember, anything that can reach orbit about Mars can reach an NEO, Venus orbit, or Mercury orbit, or even the main asteroid belt. It can always be refitted with better propulsion as such becomes available. Does it not make sense to build just one or two of these things, and use them to go all of those places, and maybe more?

GW

RobS · 2014-04-05 11:36:42

I am inclined, generally, to agree with you, GW Johnson. We are moving into an "era of reusability." When launch to Earth orbit costs many millions per tonne, mass reduction was the priority and that meant building things light and throwing them away. Reuse requires heavier construction and fuel to bring things back, or new aerobraking techniques we haven't yet perfected. Falcon Heavy and orher commercial launch systems that follow and have to compete with Falcon will bring launch costs to LEO down to 2 million per tonne, maybe even 1 million per tonne.

Any system for taking humans to and from Mars should be reusable. We will need at least two of them, because mission 2 probably has to depart for Mars a few months before mission 1 returns (assuming chemical propulsion), and mission 1's equipment will need on-orbit servicing. No doubt, every four years the system will be upgraded; better life support, more efficient solar arrays, and even larger, lighter hab modules (the old one could be added to ISS or its successor). The task of upgrading should be given to the crew that will be taking the craft to Mars; that way they will know exactly what is there and will get advice from Houston while they are less than a light-second away.

Who knows where we will go next. Probably a near-earth asteroid. The equipment for Mission 1/3/5 or Mission 2/4/6 could be used for that during the 18 months it waits at Earth for its next trip to Mars, or as a shake-down mission before its first Mars trip. After that, maybe Ceres?

Ceres: Delta-v not much more than Mars, but the voyage is much more (about a year each way) and ISRU will require considerable development because water on Ceres will be underground (where there appears to be a LOT of it). It may be possible to extract water from Cererean clays. The very low g of Ceres probably means the stay can't be very long. Artificial gee is probably essential for the voyage out and back (to counteract the essentially zero-gee of the surface stay!), and nuclear power is probably essential (solar constant is 10% of earth; maybe mirrors will solve the problem, though). Politically, this trip would be hard to justify. Nuclear power might be a show stopper if it hasn't already been developed for Mars.

Venus: The delta-v to Venus is less than to Mars and you can get there in 90-120 days easily, but once there you will need to stay in Venus orbit, and you will need all the fuel for a return trip to Earth (which needn't be too much if you go into an elliptical orbit), and the only reason to go to Venus is to telerobotically operate equipment on the surface (which will be devilishly difficult and expensive to create). Presumably we will need to send automated equipment to Venus for a decade or so and learn how to build stuff that can handle the heat and pressure before we send people. If all the surface stuff breaks, after all, there won't be anything for them to do but orbit round and round a hellhole until the launch window back to Earth opens. Powering equipment on the surface of Venus may be a technological challenge we still can't handle. A small sodium-cooled nuclear reactor? Can we make electronics that function at 400 Celsius? Can we make it at room temperature, send it to Venus, land it, and let it heat up and expand that much, and still work? Do you need people in orbit if all they're doing is running balloons and solar-powered airplanes 40 kilometers above the surface? I don't see people going to Venus any time soon.

Mercury: You can get to Mercury orbit quickly, but the delta-v is pretty steep; chemical propulsion would be very difficult to use, though possibly solar thermal would work well to get into Mercury orbit and get back out of it later (if you can keep your hydrogen from boiling off in between!). I think I'd park the mother ship at the Mercury-solar L2 point in Mercury's permanent shadow, or maybe in the penumbra where a little bit of solar energy is available, but not too much. From Mercury-solar L2 to the north or south pole, the delta-v is something like 5 km/sec. The poles are rather similar to the poles of the moon, except they have more sun AND more water. Basically, getting to Mercury needs twice the delta-v as getting to Mars and landing/taking off takes twice as much as the moon. Doable, but when would we have the political will to do it? probably not until commercial launchers have made LEO a much more cheaper place to reach.

Callisto: A lot farther than Ceres, a lot more delta-v to get there, though the delta-v to enter orbit around Jupiter and land on Callisto is also about 5 km/sec (like Mercury) and we know there's plenty of ice. If chemical fuel is very cheap in LEO (1 million per tonne) about a 9 km/sec delta-v from LEO (which the Pluto probe needed) would get people to Jupiter in a year.

Whatever we build for Mars could be upgraded/modified for these other voyages, but I suspect by the time we do any of them, we'll need a second generation of equipment and the Mars equipment will be partially obsolete.

RobS · 2014-04-05 16:45:43

This is from the Wikipedia page for New Horizons:

Launched directly into an Earth-and-solar-escape trajectory with an Earth-relative velocity of about 16.26 km/s (58,536 km/h; 36,373 mph) [on January 19, 2006] it set the record for the highest velocity of a human-made object from Earth. Using a combination of monopropellant and gravity assist, it flew by the orbit of Mars on 7 April 2006, Jupiter on 28 February 2007, the orbit of Saturn on 8 June 2008; and the orbit of Uranus on 18 March 2011.

That shows you what you can do, even with a human mission, if hydrogen/oxygen propellant is reasonably cheap ($1 million per tonne with a reusable Falcon Heavy) in low earth orbit. New Horizons passed the orbit of Mars in 78 days (2 1/2 months!), reached Jupiter in 13 months and 9 days, crossed the orbit of Saturn in 2 years, 4 1/2 months (with a Jupiter gravity assist), and reached Uranus's orbit in a bit over 5 years. Of course, if you reach Mars in 78 days, you can't use aerocapture because you're going too fast, so you need fuel to slow down. But in Jupiter's powerful gravity well, a small burn will capture you and the Galilean moons can shape your trajectory. For Saturn, Titan's "fluffy" atmosphere is aerocapture nirvana.

Quaoar · 2014-04-06 11:00:59

GW Johnson wrote:

This might be off-the-wall, but it seems to me that converting a propellant tank to habitable space involves a lot of effort and maybe significant hardware weight that could be avoided by using a different approach.
Why not just build the habitable spaces as dedicated modules, and then dock propellant tanks and propulsion items to it, in space. All of these may then be "optimized" for their roles, especially if you want to re-use this vehicle for multiple missions. The only things needing replacement are the life support consumables and the propellants, and periodically for maintenance, the engines. GW

To perform docking, has every module an indipendent RCS?

Last edited by Quaoar (2014-04-06 11:01:38)

GW Johnson · 2014-04-07 08:48:45

I would think every module should have its own thruster system to maintain attitude until a vehicle can dock with it and put it where it needs to go. The trouble is spin, can't let that happen. But, it's a minimal thruster rig that can be turned off, or even removed and repurposed.

GW

SpaceNut · 2014-04-07 21:23:01

Other issues are the power source while we wait for the next module for link up and fuel reserves to maintain the spin to a manageable level, versus a free tumble out of control.

Quaoar · 2014-04-08 07:26:28

GW Johnson wrote:

I would think every module should have its own thruster system to maintain attitude until a vehicle can dock with it and put it where it needs to go. The trouble is spin, can't let that happen. But, it's a minimal thruster rig that can be turned off, or even removed and repurposed.
GW

Why not to add a thermal protection on the belly to perform aerocapture?
Mars atmosphere has a variable density and may be dangerous to aerocapture with LOX and LH2 in the tanks: so your modular spaceship can do Mars arrive propulsively and use aerocapture only for Earth for return, when the tanks are almost empty and the ship is lighter, saving hunderds tons of propellant mass.

Last edited by Quaoar (2014-04-08 07:28:02)

GW Johnson · 2014-04-08 09:41:57

I may be wrong, but there is a shape issue with aerocapture, entry, even just plain hypersonic flight. You cannot have one module's shock wave impinging upon an adjacent module. That causes extreme shock-impingement heating, and is what nearly cut the tail off one of the X-15's on its Mach 6.7 flight decades ago. That bird was carrying an experimental scramjet nacelle on its ventral fin stub, instead of a nice "clean" fin. The compression spike shock angled right up through the tail section in a beautiful Mach 6 conical shock pattern. Cut away Inconel-X superalloy structure, it did.

To do aerocapture (or entry, or hypersonic flight) you want one single very clean shape exposed to the hypersonic wind blast, such that none of the shock waves it inevitably sheds can directly impinge upon adjacent surfaces. For small space probes, this is easy to do as a single heat shield panel of some kind, behind which you can hide pretty much whatever you want. For a big cluster, I have doubts this can be done. At least in any practical way.

GW

RobertDyck · 2014-04-08 10:27:27

RobS wrote:

We will need at least two of them, because mission 2 probably has to depart for Mars a few months before mission 1 returns (assuming chemical propulsion), and mission 1's equipment will need on-orbit servicing.

That's one reason I argue for the original time frame from Mars Direct: 6 months to Mars, 14 months on the surface, 6 months back. Or to say that in days: 180 days to Mars, 425 days on the surface, 180 days back. This means 425 day surface stay, not 500. The result is your first mission returns before the second departs. There's a lot of reasons you want to do that.

There have been proposals for 500 or 600 day surface stay, but keeping to 425 days means the first mission arrives home before the second departs.

Remember, to get anything past Congress we have to keep cost down. To quote from the movie Contact: "First rule in government spending: Why build one when you can have two at twice the price?" If you want Congress to actually approve anything, you have to stop this.

Last edited by RobertDyck (2014-04-08 19:01:20)

Quaoar · 2014-04-08 15:30:17

GW Johnson wrote:

I may be wrong, but there is a shape issue with aerocapture, entry, even just plain hypersonic flight. You cannot have one module's shock wave impinging upon an adjacent module. That causes extreme shock-impingement heating, and is what nearly cut the tail off one of the X-15's on its Mach 6.7 flight decades ago. That bird was carrying an experimental scramjet nacelle on its ventral fin stub, instead of a nice "clean" fin. The compression spike shock angled right up through the tail section in a beautiful Mach 6 conical shock pattern. Cut away Inconel-X superalloy structure, it did.
To do aerocapture (or entry, or hypersonic flight) you want one single very clean shape exposed to the hypersonic wind blast, such that none of the shock waves it inevitably sheds can directly impinge upon adjacent surfaces. For small space probes, this is easy to do as a single heat shield panel of some kind, behind which you can hide pretty much whatever you want. For a big cluster, I have doubts this can be done. At least in any practical way.
GW

We can have a one piece 40-50 tons triconic habitat with thermal protected belly that detatchs from the "Johnson Express" and aerocaptures in low Earth orbit. The rockets and lightweight almost empty tanks insert propulsively, rendez-vous and dock again with the hab, ready to be refueled and reused.

On Mars orbit we can choose to do an all propulsively inserction or a split and redocking arrive, with the full loaded habitat that aerocaptures, the rest of the ship that inserts propulsively and the lander that performs an aerocapture followed by an atmospheric entry.

An alternative may be to have a 20 meters diameter ADEPT like deployable aeroshell with all the modules that dock concentrically around the habitat, forming a compact cluster inside the heat shield. After aerocapture, the modules can detatch and redock in line forming a long baton for artificial gravity.

Last edited by Quaoar (2014-04-08 15:35:23)

RobertDyck · 2014-04-08 16:05:05

And I was concerned with my design. That is an Interplanetary Transit Vehicle, Dragon as escape pod, and Mars lander, all docked together. The assembly has to be balanced on a tether while rotating for artificial gravity, and has to be safely tucked behind an ADEPT aeroshell during aerocapture. Counter weight for artificial gravity would be the spent TMI stage, so the tether could be cut and the counter weight released on approach to Mars. But the ITV has to be balanced for artificial gravity, and balanced behind the aeroshell for Earth aerocapture, with Dragon but without the Mars lander. To achieve that ballance, that implies the Mars lander should be coaxial with the rest. In other words, should be on the "roof", between the ITV and tether. But the assembly would de-spin after releasing the counter weight, so zero-G as it aerocaptures. Then remain in zero-G in Mars orbit. So un-docking the Mars lander would be easy.

To avoid the tether whipping back, the tether would be released with the counterweight. That is, cut at the ITV/Lander. This requires a new tether on the MAV, so it can be used as counter weight during transit back to Earth.

Last edited by RobertDyck (2014-04-08 19:02:08)

RobertDyck · 2014-04-08 16:45:43

Updating my mission plan a bit. As previously discussed, the ITV would require Falcon Heavy instead of Falcon 9.

Option 1: return crew with Dream Chaser

First mission:
- 1 SLS Block 2 for MAV (direct launch from KSC to Mars surface)
- 1 SLS Block 2 for lab & pressurized rover (direct launch)
- 1 Falcon Heavy for ITV
- 1 SLS Block 1 for TMI stage
- 1 Falcon 9 lander & unpressurized rover
- 1 Falcon 9 for Dragon
- 1 Atlas V 402 for Dream Chaser

Second mission:
- 1 SLS Block 2 for MAV
- 1 SLS Block 2 for lab & pressurized rover
- 1 SLS Block 1 for TMI stage
- 1 Falcon 9 lander & unpressurized rover
- 1 Atlas V 402 for Dream Chaser

Third mission:
- 1 SLS Block 2 for MAV
- 1 SLS Block 1 for TMI stage
- 1 Falcon 9 lander & unpressurized rover
- 1 Atlas V 402 for Dream Chaser

*Note: What I'm calling SLS Block 2 = full size upper stage with 2 J-2X engines, but 5-segment SRBs.
What I'm calling SLS Block 1 = Interim Cryogenic Propulsion Stage, 5-segment SRBs.

Option 2: return crew with Dragon

First mission:
- 1 SLS Block 2 for MAV (direct launch from KSC to Mars surface)
- 1 SLS Block 2 for lab & pressurized rover (direct launch)
- 1 Falcon Heavy for ITV
- 1 SLS Block 1 for TMI stage
- 1 Falcon 9 lander & unpressurized rover
- 1 Falcon 9 for Dragon

Second mission:
- 1 SLS Block 2 for MAV
- 1 SLS Block 2 for lab & pressurized rover
- 1 SLS Block 1 for TMI stage
- 1 Falcon 9 lander & unpressurized rover
- 1 Falcon 9 for Dragon

Third mission:
- 1 SLS Block 2 for MAV
- 1 SLS Block 1 for TMI stage
- 1 Falcon 9 lander & unpressurized rover
- 1 Falcon 9 for Dragon

Option 3: Russian (please let them stop invading Ukraine)

First mission:
- 1 Energia with EUS for MAV
- 1 Energia with EUS for lab & pressurized rover
- 1 Proton for ITV
- 1 Energia for TMI stage
- 1 Proton for lander & unpressurized rover
- 1 Angara 5P for PK space capsule

Second mission:
- 1 Energia with EUS for MAV
- 1 Energia with EUS for lab & pressurized rover
- 1 Energia for TMI stage
- 1 Proton for lander & unpressurized rover
- 1 Angara 5P for PK space capsule

Third mission:
- 1 Energia with EUS for MAV
- 1 Energia for TMI stage
- 1 Proton for lander & unpressurized rover
- 1 Angara 5P for PK space capsule

For each of these options, this assumes all missions land at the same location. They build up a base by accumulating equipment. If a mission was sent to a different landing location, then it would require the "Second mission".

RobS · 2014-04-08 18:56:31

You guys have been busy today! Robert, when you say a 425 day stay on Mars, are you making the departure from Earth later, the departure from Mars earlier, or what? And what does that do the delta-v for trans-Mars or trans-Earth injection? Cutting 75 or more days from the stay on Mars certainly makes the launch windows less favorable.

RobertDyck · 2014-04-08 19:34:42

I thought that's what Mars Direct was. But here is a NASA paper on Mars Design Reference Missions, Johnson Space Center 1997. Pages 3-36 through 3-38 lists three different trajectory options. I will summarize as outbound transit time / surface stay / return.
Short stay (opposition class): 224/30/291
Long stay (conjunction class): 224/458/237
Fast transit: 150/619/110

The text describes long stay (conjunction class) with surface stay up to 500 days. Note none exactly match what Robert Zubrin talks about. For one thing, "Long stay" does not use the express trajectory, typically 180 days. What I'm saying is a compromise between "Long stay" and "Fast transit".

Ps. Short stay includes the "Venus fry-by" during the return trip. The text also says fast transit is not available for a short stay trajectory.

Last edited by RobertDyck (2014-04-08 20:35:09)

RobS · 2014-04-08 20:27:34

The "short stay" option is basically what Inspiration Mars would use in 2021. That launch opportunity involves a Venus "fryby" on the way to Mars.

Thanks for the link, I'll take a look.

Quaoar · 2014-04-09 14:44:19

RobertDyck wrote:

And I was concerned with my design. That is an Interplanetary Transit Vehicle, Dragon as escape pod, and Mars lander, all docked together. The assembly has to be balanced on a tether while rotating for artificial gravity, and has to be safely tucked behind an ADEPT aeroshell during aerocapture. Counter weight for artificial gravity would be the spent TMI stage, so the tether could be cut and the counter weight released on approach to Mars. But the ITV has to be balanced for artificial gravity, and balanced behind the aeroshell for Earth aerocapture, with Dragon but without the Mars lander. To achieve that ballance, that implies the Mars lander should be coaxial with the rest. In other words, should be on the "roof", between the ITV and tether. But the assembly would de-spin after releasing the counter weight, so zero-G as it aerocaptures. Then remain in zero-G in Mars orbit. So un-docking the Mars lander would be easy.
To avoid the tether whipping back, the tether would be released with the counterweight. That is, cut at the ITV/Lander. This requires a new tether on the MAV, so it can be used as counter weight during transit back to Earth.

Will the rockets of the lander be used also for trans Earth injection?

Last edited by Quaoar (2014-04-09 14:47:21)

RobertDyck · 2014-04-09 15:30:02

Quaoar wrote:

Will the rockets of the lander be used also for trans Earth injection?

Nope. The lander will land on Mars surface, and it won't lift off again. The Mars Assent Vehicle will lift off, carrying crew to Mars orbit. In my design, the MAV will have extra large propellant tanks because it will be the TEI stage. So the MAV is used for Trans Earth Injection.

Last edited by RobertDyck (2014-10-27 16:03:31)

Quaoar · 2014-04-10 01:51:45

RobertDyck wrote:

Nope. The lander will land on Mars surface, and it won't lift off again. The Mars Assent Vehicle will lift off, carrying crew to Mars orbit. In my design, the MAV will have extra large propellant tanks because it will be the TMI stage. So the MAV is used for trans Earth injection.

Interesting: have you posted your design?

RobertDyck · 2014-04-10 08:26:01

Quaoar wrote:

Will the rockets of the lander be used also for trans Earth injection?

No

RobertDyck · 2014-04-10 08:28:16

Quaoar wrote:

Interesting: have you posted your design?

That's what most of this discussion is about. But it's text, not pictures. Details start on the second page of this discussion, click here: http://newmars.com/forums/viewtopic.php … 45#p116645

RobertDyck · 2014-06-28 19:08:10

One issue with any Mars mission, is that traditional aerospace contractors ("old space") are still drooling over the $450 billion price tag, in 1989 dollars. That's $750 billion in today's money. Subtract about $100 billion for ISS, and something for SLS and Orion, I still argue most of the work for a life support system has already been finished, but that still leaves somewhere between $500 billion and $750 billion in today's money. When Congress saw the price tag in the 90-Day Report in 1989, they immediately and loudly said "No!" However, "Old Space" still has the delusion that they'll get it. Any plan to return to the Moon, any plan to use Orion for the Moon then proceed on to Mars, is this plan. The plan for $500 billion to $750 billion in addition to what has already been spent. That's NASA's "current" plan. Congress said no way in hell will they ever pay that much. But "Old Space" just will not let it go.

That said, my mission plan is not all that different from Mars Direct. A reusable spacecraft from ISS in Earth orbit to high Mars orbit, and back. Expendable stages for TMI and TEI. One optimization is the MAV is the TEI stage, so all return propellant via ISPP. This means you use a tether and cut that tether for aerocapture at each planet. Want an image? Here's one of the Mars Direct habitat with heat shield and attached to the TMI stage with a tether. This is an early image, showing the hab with just one floor. This is basically what I envision for the ITV (Interplanetary Transit Vehicle). But the heat shield would be capable of aerocapture at both planets, and aerobraking at Earth to drop down to LEO for rendezvous with ISS.

71511-img3

The floor plan for that original vehicle had the airlock on the single pressured story. The airlock is in the centre, with food storage cupboards all around for radiation shielding. The airlock is the radiation shelter. I like this idea; stick with it. But life support must be accessible for maintenance/repairs. So for the ITV, replace the laboratory with life support equipment. The ITV would have docked to it a single Dragon space capsule as an emergency escape pod in case aerocapture at Earth fails. During transit to Mars, it would also have the Mars lander docked.

Here's an idea. Since Dragon would only be needed when returning to Earth, and the MAV requires a capsule anyway, design the MAV in two parts: Dragon capsule, plus propulsion stage? Dragon would remain docked to ITV, but the spent propulsion stage would be the counterweight at the end of the tether. Upon approach to Earth, the tether would be cut, the ITV with Dragon de-spun, then aerocapture in Earth's upper atmosphere. I had originally talked of docking Dragon permanently, and reusing for each mission. Use DreamChaser to ferry crew to ISS, with the ITV docked to ISS for crew return and prep for next mission. The MAV would use a light-weight unpressurized fairing, with astronauts riding in spacesuits from Mars surface to the ITV. Would it be better to drop the capsule all the way to the surface of Mars? Use a full Dragon for Mars ascent? That would be more weight for the MAV to lift off Mars, but less weight for the ITV to carry to Mars.

Naw! That creates a new problem. One advantage with my mission plan is additional contingency. The ITV is used for transit to Mars and back, so if a free return is necessary, the crew is already in their return vehicle. Furthermore, all food and life support supplies for return to Earth travels with astronauts from Earth, so again in case a free return is necessary, they already have all that with them. Keeping with that philosophy, the emergency escape pod (Dragon) must depart Earth with astronauts.

So doing this, Dragon would be docked to the underside of the airlock. Between the single story hab and the aerocapture heat shield. That keeps it axial, so balanced for rotation. It also means the heat shield will protect Dragon as long as Dragon isn't used. And it means Dragon won't be up-side-down. So easy to access during rotation. And oriented correctly so astronauts can sit in Dragon during Earth aerocapture. The top of the airlock would have an APAS docking hatch so it could dock with ISS.

Where would the Mars lander attach? To the top? So preparing the ship for the next mission would require detaching from ISS, and docking the lander to the APAS hatch? That would leave the Mars lander up-side-down during rotation.

Last edited by RobertDyck (2014-06-29 06:15:48)

JoshNH4H · 2014-06-28 20:34:08

Robertdyck,

I quite like your mission architecture, and certainly the idea of leaving your transfer vehicle in a high orbit while landing as little mass (in smaller increments) on the surface is a great one. Especially so now that orbital assembly has been proven on ISS.

My argument with GW was a bit more fundamental than mission architecture, though. Mission philosophy, perhaps. Big mission vs. small mission. I can see that you favor small missions. Why is that? What, in your opinion, is the purpose of the first mission? What should it accomplish?

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