Yet another Mars architecture

RobS · 2015-05-27 21:01:40

Yes, I was using 70 metric tonnes to LEO for Block 1, because it's the only SLS that has been funded and I have my doubts something heavier will get funded. But if you want to use 130 mt, that's about the number I was using for 2 block-1 (70 mt to LEO) launches.

RobertDyck · 2015-05-27 21:10:03

Wikipedia for SLS

In 2013, NASA and Boeing analyzed the performance of several second stage options. The analysis was based on a second stage usable propellant load of 105 metric tons, except for the Block 1 and ICPS, which will carry 27.1 metric tons. These options are the following:
Without an upper stage, the SLS would be capable of delivering 70 t to low Earth orbit (LEO), and, using the ICPS, 20.2 t to Trans-Mars injection (TMI) and 2.9 t to Europa.
A 4 engine RL10 upper stage could deliver 93.1 t to LEO, 31.7 t to TMI and 8.1 t to Europa.
A 2 engine MB60 (an engine comparable to the RL60) upper stage could deliver 97 t to LEO, 32.6 t to TMI and 8.5 t to Europa.
A single engine J-2X upper stage, with higher thrust than other options, could deliver 105.2 t to LEO, but the lower specific impulse of the J-2X would decrease its beyond-LEO capability to 31.6 t to TMI and 7.1 to Europa.

This still uses the 4 SSME core stage, and 5-segment SRBs. Block 2 is supposed to use 5 SSME, and advanced SRBs.

::Edit:: Grumble, grumble, grumble! Cancel block 2! The only useful SLS! Expletive inserted. Grumble, grumble, grumble!

Last edited by RobertDyck (2015-05-27 21:12:04)

RobertDyck · 2015-05-28 11:44:55

RobertDyck wrote:

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.

Here is that slide:

Last edited by RobertDyck (2015-05-28 14:21:36)

RobS · 2015-05-28 12:12:31

So Robert, what TMI throw weight are you assuming for your system? I guess that's the useful question to ask. If you want people to offer suggestions to your plan, what units of mass are we assuming? Or are we assuming that with different combinations of vehicles, we can start with any reasonable mass in LEO?

RobertDyck · 2015-05-28 12:52:52

That's the thing. My first post was on the second page of this discussion. It was a very rough plan, without exact launch weight. Back then Putin wasn't the problem he is today, so I tried to split up the mission to fit on Energia. I got that idea from Robert Zubrin's book: The Case For Mars. That meant TMI throw weight of 28.5 metric tonnes. Based on the Mars Direct ERV, an MAV with unpressurized capsule should easily dock with the ITV in Mars orbit, with sufficient propellant for TEI. But we need to work out exact mass.

To answer your question, I guess we could assume SLS with an upper stage that has 105 metric tonnes of LH2/LOX propellant, and a single J-2X engine. According to the Boeing study cited by Wikipedia, that gives 31.6 metric tonnes direct throw to TMI, or 105.2t to LEO. However, mass to LEO is usually 185km. If we assemble at ISS, we can use the station as a construction shack (house astronauts), and use the station arm for construction. But that means 400km orbit +/- 10km. The Shuttle could lift 28.8t to 185km, or 16.05t to ISS. So assuming the same ratio holds, that should allow SLS to lift 58.6t to ISS.

Of course that mass to ISS has to include something to rendezvous with ISS. We discussed sending the centrifuge module to ISS. It required the Shuttle because it doesn't have propulsion or guidance. My last suggestion was to use an ATV-based service module, similar to the one for Orion, but with the ATV rendezvous radar and guidance system. Ariane 5 should be able to launch the Centrifuge Accommodation Module with such an ATV-based service module. But launching components for a Mars mission would require similar rendezvous. The propulsion stage could guide itself, but what about other components? Also an ATV-based service module? The one for Orion masses 12,337kg.

RobS · 2015-05-28 13:09:44

I wouldn't assume that the mass to ISS is barely more than half than to a 185 km orbit. The delta-v to get there from a 185 km orbit can't be that much; hundreds of meters per second at most. The limitation to ISS works for the mass of the shuttle itself (which should be thought of as payload as well) PLUS the usable cargo. The shuttle had to make the transition from a very low orbit to ISS using its small NTO/MMH engines, right? The hydrogen/oxygen tank drops off just short of orbital velocity, falls back to Earth, and burns up.

Furthermore, if there isn't a lot of assembling to do--just docking--that can be done in automated fashion in a low orbit, then the crew can fly up for TMI.

If you use a round 100 tonnes the LEO and 30 tonnes to TMI, you have some rough and usable numbers. That could be an SLS medium or two Falcon Heavies. Or, assume an SLS large with 130 tonnes to LEO and 43 tonnes to TMI; that's the rough equivalent of three reusable Falcon Heavies.

There must be data on the cargo of other rockets to LEO and the ISS orbit which would provide a better idea. But you need a number in Earth orbit first, it seems to me.

RobertDyck · 2015-05-28 13:35:49

Actually, Shuttle launched directly into the higher orbit of ISS. But not at the point where ISS was, rather the point where KSC passed under that orbit as Earth rotated. It then had to catch up. But you do have a point: Shuttle had to lift itself plus cargo. Shuttle reference manual on the NASA website said orbiter mass on landing was 104t. Not sure which orbiter. Endeavour had empty mass of 78t, gross liftoff mass of 110t. If we use the 104t figure, then 28.8 + 104 = 132.8t to 185km orbit, or 16.05 + 104 = 120.05t to ISS @ 407km orbit. Based on that ratio then SLS with a J-2X upper stage should lift 95.1t to ISS. Again that lift mass has to include the service module to rendezvous with ISS, and hover close enough for the station arm to grab it. If you assume the ATV-based service module from Orion, then subtract 12.3t.

SpaceNut · 2015-05-28 19:04:56

I do recall and the work on the life spport comparison to the ISS showed that it was close to the value in the image table and I started a topic of ISS resupply of the consumable so as to prove out if the mass for food / water or oxygen to start with and I think that its not close as the table does not include water....

RobertDyck · 2015-05-28 19:30:38

From Light weight nuclear reactor, updating Mars Direct
Based on equipment installed on ISS.

Waste Collector Subsystem (space toilet): 246 lbs
Water Processor Assembly: 1,450 lbs
Oxygen Generation Assembly: 383 lbs
- power supply cart: 291 lbs
Sabatier reactor: ?
CO2 sorbent: 105 lbs
Dehumidifier: 212.6 lbs
Urine Processing:
- Distillation Assembly (DA): 166.6 lb
- Pressure Control and Pump Assembly (PCPA): 98.7 lbs
- Fluids Control and Pump Assembly (FCPA): 100.5 lbs
Total: 3053.4 lbs = 1,385 kg (but Sabatier not included)

RobertDyck · 2015-05-28 19:57:45

Mass figures for Mars Direct were updated a few times. NASA technical reports server has a copy of proceedings of a symposium held at Pennsylvania State University, June 25-29, 1990. One of the presentations was Mars Direct by Robert Zubrin and David Baker. That one already talked about expanding the hab to have a second deck, and mass allocations are a little different. The useful part of that one is actual mass allocation for Entry-Descent-Landing. It used a common EDL stage for the hab and ERV. And different again in "The Case For Mars", published 1997. But always sized to fit on a pair of Ares launch vehicles. That was to include a pair of advanced solid rocket boosters, 5 SSME, and an upper stage with a single J-2S engine. SLS block 2 essentially is Ares. I guess I'm asking to update again; but this time with my ideas. One of my ideas is a reusable ITV that looks like the upper story of the Mars Direct hab. I had considered replacing with a zero-G hab like an ISS module, if NASA was too anal about artificial gravity. But you guys make convincing arguments to stick with the original plan: artificial gravity using Robert Zubrin's idea. I thought GW would be interested since this would provide artificial gravity for both transits.

kbd512 · 2015-05-29 18:44:49

RobertDyck wrote:

Mass figures for Mars Direct were updated a few times. NASA technical reports server has a copy of proceedings of a symposium held at Pennsylvania State University, June 25-29, 1990. One of the presentations was Mars Direct by Robert Zubrin and David Baker. That one already talked about expanding the hab to have a second deck, and mass allocations are a little different. The useful part of that one is actual mass allocation for Entry-Descent-Landing. It used a common EDL stage for the hab and ERV. And different again in "The Case For Mars", published 1997. But always sized to fit on a pair of Ares launch vehicles. That was to include a pair of advanced solid rocket boosters, 5 SSME, and an upper stage with a single J-2S engine. SLS block 2 essentially is Ares. I guess I'm asking to update again; but this time with my ideas. One of my ideas is a reusable ITV that looks like the upper story of the Mars Direct hab. I had considered replacing with a zero-G hab like an ISS module, if NASA was too anal about artificial gravity. But you guys make convincing arguments to stick with the original plan: artificial gravity using Robert Zubrin's idea. I thought GW would be interested since this would provide artificial gravity for both transits.

There's no funding for development of an Ares class launch vehicle and there probably never will be. The addition of a 5th RS-25 to SLS would require a redesign of the core stage. The original concept for Ares V was designed and sized for manned Mars missions, but NASA chose to screw around forever with details that were already foregone conclusions, like liquid vs solid boosters and various side mount cargo solutions, instead of simply designing what would have met throw requirements while maximizing use of exiting hardware.

The 5 segment SRM's were created to spend money on the vendor's pet project. The original 4 segment SRM's, with minor modifications to remove subsystems related to recovery, would have provided a heavy lift launch vehicle with minimal development cost. Instead, the cockamamie Ares I and Ares V nonsense was inflicted upon NASA and that nearly lead to the cancellation of the entire Ares (SLS) program.

As far as the upper stage is concerned, use of RL-10's, RL-60's, or RS-25's would make the most sense and would have been preferable to development of new J-2's. The development program for SLS can only be properly labelled a spending program.

There's no amount of polish that can change the fact that SLS is a turd. The gee-whiz factor is mostly, "Gee whiz, we spent more money and time in development on SLS than Saturn V and we still don't have a Saturn V class launch vehicle."

I want a true heavy lift rocket, minimum 125t throw, but not if it's every bit as expensive as STS and then some.

Regarding NASA's artificial gravity aversion, the agency already has ISS-derived hardware for deep space habitation in development. If the program was properly funded by defunding Orion, perhaps we could develop CL-ECLSS and active radiation shielding. I have no clue what the issue is with artificial gravity, but I'd choose to skip focus on that specific issue for sake of development of mission hardware capable of taking humans to Mars.

In any event, it would appear that NASA is trying to implement Mars Direct while not calling it Mars Direct to avoid NIH syndrome.

RobS · 2015-05-29 19:49:30

This is the sad situation we are in, KBD512. If we get the block-2 SLS (Senate Launch System) with 130 mt throw weight, it will be because Congress decided to create a very big pork barrel project and will build a very expensive rocket. If NASA is then mandated to use it, it will soak up a big chunk of the human spaceflight budget and make moon and Mars exploration prohibitively expensive. Politics has sunk to an incredible level of corruption.

Meanwhile, Musk is upgrading the Falcon 9 with a more powerful Merlin-D and a larger second stage so that it can launch bigger satellites to GTO AND bring the first stage back for a landing. The augmented Falcon 9 is supposed to fly this summer. The larger Merlin-Ds--with superchilled LOX and kerosine to densify them and fit more in the first stage tanks--will be the side sticks for the Falcon Heavy (but not the central core, for some reason). Who says Falcon Heavy will only put 55 mt in low Earth orbit? That was the older version of the Falcon 9. With bigger side sticks and a bigger second stage he might get that up to 60 or 65 mt. And if the reusable version of the Falcon Heavy flies (with an expendable the second stage, but it will have only 1/28 of the engines anyway, so won't be that expensive to throw away) and it manages to lift 40 mt to LEO for, say 40 million dollars, the entire game changes. The SLS will be unusable; it may even be politically unusable. We will have to think in terms of fuel depots and refueling the Falcon 9 second stages for TMI. Kerosine doesn't have a great Isp, but who cares if it costs only $1 million per tonne? Furthermore, at prices like that, solar electric will be much more costly, and therefore will not be a reasonable choice.

I think this scenario is far, far more likely than an SLS able to place 130 mt in LEO for a billion dollars, and it's eight times cheaper per tonne anyway. The SLS might be 2 billion per launch; so much the worse. We know Falcon Heavy will be $110 million or so to put 55 mt to LEO, and that's 2 million per tonne. It's suppose to fly for the first time later this year (though apparently without propellant cross feed; they want to start simple).

My conclusion from all this is to forget Energia and forget SLS. Think in terms of docking fuel modules and payload together in LEO or at ISS, which can't be that difficult. Choose a TMI throw weight you want to aim for; 30 mt, 40 mt, whatever. We don't know how we will get that payload to orbit, or what propellant we'll use to get it to TMI, because of the uncertainty over launch vehicles; that's a detail to settle in a year or two.

RobS · 2015-05-29 20:32:55

In terms of landing on Mars, also, I think we need to take our lead from Musk. After the recent successful test of the superdracos, he commented that the system he is developing can be used to land cargo on the moon, Mars, and Europa. One basic system that can be scaled up--so far, everything he has developed has led to scaled up versions--would be cheaper and more reliable because of larger scale production and increased flight experience.

The key element is being able to do hypersonic retropropulsion. Like Clark, Musk appears to envisage a small deorbit burn, aerobraking, then terminal retropropulsion. He will be doing it with the Dragon V-2 here on Earth in a few years (the first ones will parachute into the ocean; again, he develops new technology incrementally). I wouldn't be surprised if he does an unmanned landing of a Dragon on Mars in less than a decade. It he can land 1-2 useable tonnes of payload on Mars, as he says, he can do a sample return mission directly back to the Earth (the rocket would launch through an opening in the top of the capsule and presumably a little rover would go in and out of a door to retrieve a sample).

For landing on Mars, presumably you want to replace the hypergolics with methane and oxygen, producing what one could call methane-superdracos. It may be that one could replace the hypergolics with methane and oxygen even for the Dragon V-2. This has the disadvantage that methane and LOX are a lot colder than hypergolics and are basically in the capsule with the passengers. But it has the advantage of safety; the hypergolics require more complex debarkation for the passengers because there has to be an inspection to make sure there is no toxic hypergolic fuel leaking first. Landing on the moon, Mars, and Europa would require a lot more delta-v anyway, so possibly the methane-LOx and even the methane-superdracos could be relocated into the trunk. That would mean, for Mars landings, relocating the heat shield (or adding a second, lighter heat shield for Martian conditions).

The other thing one will want for Mars is a larger vehicle, at least 5 meters in diameter rather than 3.8 meters. Think of a larger version of the Dragon's trunk, with landing legs and a heat shield on the bottom and with its own methane super-dracos and tankage able to hold 20-40 mt of propellant. That's the basic Mars landing vehicle I envision. For cargo, you build the methane superdracos into the upper walls of the trunk so that the cargo hold is underneath, closer to the ground, for ease of unloading. For passengers, you put a capsule or a passenger compartment on top and still have the cargo hold underneath. (You could even build your passenger compartment into the cargo hold underneath if you want; it could be a little inflatable bubble.) If you need large tanks for liquid hydrogen storage, you add them to the cargo hold or extend the length of the trunk. You design the thing to transport about 15 mt of cargo to the surface, or a passenger compartment and 10-12 mt of cargo. It needs propellant equal to about a third of its total mass, so if the cargo, passengers, and structure total 20 mt, you need about 10 mt of propellant to land it on the surface. If the dry mass for launch back to orbit is 5 mt and it is able to hold 30 or 40 mt of methane and LOX (manufactured on the surface, perhaps partly from 2 tonnes of liquid hydrogen) then it can probably carry the fuel to push a 20 mt transhab in a high Mars orbit back to Earth.

That's the sort of vehicle I envision for Mars landing. It could also be used for lunar expeditions.

RobertDyck · 2015-05-29 21:50:12

One problem with Falcon 9 Heavy is that the side sticks are taller than the core module. That provides more propellant, so greater lift weight. One justification is the upper stage sits on the core module, the side sticks don't have that. The reason I call this a problem is if you try to mount an 8.4 metre habitat (outside diameter). When we discussed a self-launching space station, I pointed out that a wider upper stage would overlap (be in the same space as) the nose cone of the side sticks. You could stack a wide hab on top of the existing upper stage, it wouldn't overlap, but that would affect high speed air flow during launch. With the current 5 metre fairing, high speed air flows on all sides of the nose cone. So you don't have to worry about side stick separation. With an 8 or 8.4 metre fairing, air would flow across the outboard portion of the nose cone, but the inboard portion would be "shaded". That would push the side sticks into the core. Where do side sticks separate? While still inside the atmosphere? Would this affect separation? How would this affect aerodynamics?

One argument to this has been to use a TransHab / Bigelow hab. I'm concerned whether a soft hab would stand up 26 years and 12 transits to Mars and back, the life span I want for the ITV. And a soft hab would require a rigid floor, because artificial gravity.

kbd512 · 2015-05-30 00:23:45

RobertDyck wrote:

One problem with Falcon 9 Heavy is that the side sticks are taller than the core module. That provides more propellant, so greater lift weight. One justification is the upper stage sits on the core module, the side sticks don't have that. The reason I call this a problem is if you try to mount an 8.4 metre habitat (outside diameter). When we discussed a self-launching space station, I pointed out that a wider upper stage would overlap (be in the same space as) the nose cone of the side sticks. You could stack a wide hab on top of the existing upper stage, it wouldn't overlap, but that would affect high speed air flow during launch. With the current 5 metre fairing, high speed air flows on all sides of the nose cone. So you don't have to worry about side stick separation. With an 8 or 8.4 metre fairing, air would flow across the outboard portion of the nose cone, but the inboard portion would be "shaded". That would push the side sticks into the core. Where do side sticks separate? While still inside the atmosphere? Would this affect separation? How would this affect aerodynamics?

Development of the 8.4M (Skylab) habitat module only makes sense if you're using SLS, although F9H/FH could be modified to push empty habitats to ISS. It would be great if we had nice fat habitat modules for our astronauts to go to Mars in, but it's pretty far from a mission requirement. NASA's current approach to DSH design is to use well proven ISS hardware that doesn't have to be completely re-tested to perfection. My take on this is the same as Zubrin's. We go to Mars with the mission hardware that we have. That mean's ISS hardware, which does happen to fit within existing F9H/FH payload fairings. If there's money for development of entirely new habitats, great. Again, it's not a requirement.

It's my understanding that there are some technical problems with using payload fairings larger than ~1.5X the core diameter, but I don't know how severe the problems are or how expensive it would be to redesign F9H/FH to use payload fairings capable of containing 8.4M diameter habitat modules. My guess is that if the payload is light enough, the interfaces between the payload and the core stage are strong enough, and the engines can gimbal fast enough and precisely enough, then it's not a showstopper. This would be a great question for a rocket scientist to answer.

RobertDyck wrote:

One argument to this has been to use a TransHab / Bigelow hab. I'm concerned whether a soft hab would stand up 26 years and 12 transits to Mars and back, the life span I want for the ITV. And a soft hab would require a rigid floor, because artificial gravity.

I don't want NASA to screw around with a new habitat module design for another decade or two while multiple opportunities to send humans to Mars are lost. In a soft shell habitat, properly designed fabric flooring should still be rigid enough to enable the use of artificial gravity once the habitat is pressurized.

A near three decade operational life is asking a lot of any habitat module. Naturally, we'd want to maximize the operational life of the ITV/MTV and surface habitats to reduce the cost of an exploration campaign. However, an ITV/MTV design capable of providing decades of continuous service would definitely not be minimum mass.

RobS · 2015-05-30 07:43:36

A rigid floor certainly isn't a problem; once an inflatable is inflated, all sorts of stuff can be added to it, including rigid floor panels, if they are necessary at all. It may be that an inflatable can handle 12 transits over 26 years. In the next 5 years we'll have a lot better idea, as the Bigelow system acquires more experience. The walls of the inflatables are close to a foot thick and are supposedly as hard as concrete. They have triple thick layers that are air tight. So they are quite tough.

But if the shell costs, say, $100 million, why worry about 12 transits? The hab will require refurbishment after every transit anyway; new life support equipment and reaction control systems. Some things will be on a refurbishment/replacement schedule every transit, some every two transits, etc. If the shell lasts only 6 transits, that's not a huge loss.

RobertDyck · 2015-05-30 10:08:09

The Constellation project of George W. Bush was a redux of Apollo. It included Orion, Ares V to launch the Altair lunar module, and Ares I to launch Orion. The upper stage of Ares V was to have enough propellant left for TLI of the entire stack. The Apollo service module was used for Lunar Orbit Insertion (LOI) with the Lunar Module (LM) attached, and have enough propellant left for Trans-Earth Insertion/Injection (TEI) of the CSM only. The Orion service module had enough propellant for TEI only; the descent module of Altair would perform the LOI burn. Obama cancelled Constellation, but the Senate resurrected this plan. SLS block 2 was to do the job of Ares V, and SLS block 1 was to do the job of Ares I. So the mission of SLS is to send Orion back to the Moon. But SLS block 1 is not powerful enough to do it. SLS block 1 can only lift Orion to Earth orbit; high Earth orbit at best. If block 2 is cancelled, then there's no longer any mission for either Orion or SLS. You can't use Orion to transport crew to ISS. Orion has 28t total launch weight including full propellant tanks, LAS, and fairing. CST-100 has total launch weight of 10t, and can carry 7 astronauts instead of 6. That means CST-100 can be launched by Atlas V, while Orion requires SLS block 1. And Dragon has a total launch weight of 8t, also carries up to 7 astronauts, and launched by Falcon 9. And Sierra Nevada is still puttering away at DreamChaser, also designed to be launched by Atlas V. There's no way you could justify Orion or SLS if their only mission is to service ISS.

Of course one fear is Boeing wants to build Gateway station. That's another space station, this time in Earth-Moon L2. Only Orion/SLS could reach it. Of course Dragon launched on F9H could reach it as well, so Boeing's dream of another monopoly is dead before it starts. But seriously, do we want to build Orion and SLS block 1 just for a new space station?

I want to use SLS block 2 for Mars. If not my plan, then Mars Direct. Justification for SLS was to resurrect Constellation. I feel the Moon is "been there, done that". But if block 2 is cancelled, then what's the point of SLS at all?

Last edited by RobertDyck (2015-05-30 14:31:21)

RobS · 2015-05-30 12:58:12

The point of SLS block 1 was jobs; that's why it has been derisively called the "Senate Launch System." NASA didn't want it and even said so, but it got SLS anyway because the Senators in Alabama, Florida, and Texas wanted it. That's why I referred to corruption. It is corrupt politics that builds something to bring jobs to a place when there is no need for it.

NASA is now saddled with a burden of government corruption at the legislative level. A NASA study indicated that Falcon 9--which cost Space X 300 million to develop--would have cost NASA 3.5 billion to develop. The Dragon V-2 is costing a tenth as much as Orion and a bit more than half as much as Boeing's CST. Dragon V-1 cost $500 million, if I remember right. Our only hope for getting to Mars is for NASA to set aside a rather small slice of its total budget for commercial efforts. I suspect Space X could return humanity to the moon for a few billion dollars by 2022 or so. Musk has already said he can put people on Mars by the late 2020s. He is worth billions, Space X is valued at $8 to 12 billion, he has said that Mars is his goal, and Space X is NOT publicly traded; Musk owns more than half of the shares. So what will stop him? Perhaps a heart attack; he works 16 hours a day and runs three companies. He can put human beings on Mars less than $10 billion, I bet.

Musk has also said that he will unveil his Mars plan later this year or early next. That will be very interesting to see, especially the synergies. The launch market needs to grow several fold for him to bring down the price of launches to orbit because if he reuses equipment, he has to slow down the manufacturing and that raises the production cost per unit. So he is going into the satellite business.

No doubt he will go into the space tourism business as well, probably not directly, but in an active support role. I think he will need to replace the Dragon with something bigger eventually. If he builds a two-level capsule that is 5+ meters in diameter--I figure closer to 30 cubic meters, rather than 10--he could launch 20 or more tourists to orbit at once. That would make orbital tourism and orbital hotels much more affordable, especially on a reusable Falcon 9 ($20 million per launch?). A capsule of that size could fly 10-15 around the moon at once and 8-12 to the lunar surface at once. If you have a fuel depot in LEO with fuel launched by reusable Falcon heavies and can refuel vehicles there, the price of circumlunar tourism and lunar surface tourism drops to a commercial level (or lower; two reusable Falcon Heavies could put enough fuel in LEO to push one of these larger capsules with 12 tourists to TLI for maybe $60 million?). A landing might cost 2 or 3 times more, but that could still end up being $10 million per person, eventually.

And if you want to fly astronauts to Mars, a capsule with 30 cubic meters can accommodate 2 or 3 with an attached inflatable pretty easily. If you land it on the Martian surface and attach an inflatable hab, you have reasonable accommodation; just leave the washer, drier, dish washer, and shower on the capsule! And if such a capsule design is flown hundreds of times to LEO and the moon, you have a huge pool of accumulated experience servicing, repairing, and upgrading it. That's the way to go to Mars cheaply, reliably, and often.

RobertDyck · 2015-05-30 17:04:09

Any Mars plan of all expendable equipment will have one and only one mission. After humans have set foot on the Red planet just once, Congress will get bored and move on to something else. One mission then thrown in the trash, just like Apollo.

Private enterprise to Mars? Ok. Would be nice. But they only do what's profitable. How will they get money to pay for it? they aren't going to spend billions on something that doesn't at least pay for itself. They aren't going to route profits from something else into a human mission to Mars. How will they pay for it?

Corruption? It's considered part of the job of any Congressman to bring jobs to his/her electoral district. Many have been too focused on this, at the expense of sabotaging what's best for the country. But I wouldn't call that corruption. What is corruption is if they arrange government contracts to a company in exchange for contributions to his/her election campaign. Or worse yet, directly to his/her pocket. That's called a kick-back. Frankly, I smell kick-backs.

Your list of states didn't include Louisiana. The Michoud Assembly Facility built first stages of Saturn V, then Shuttle ET, now the core stage of SLS. Without SLS, there's no need for it. That would shut down Michoud entirely. It originally built plywood cargo planes and landing craft for World War 2, then engines for tanks during the Korean War, so could be sold. Making NASA cost effective means reducing the number of centers. JPL builds unmanned probes, Glenn advanced propulsion, Dryden tests aircraft, etc. But JSC was built as a university campus because it was expected to be shut down after Apollo. It would become a campus of Rice University. And Michoud will not be needed once SLS is cancelled. To be economic, manufacture and assembly of a large rocket should be done beside the launch pad. Manufacture of SLS stages and main engines should be done immediately beside the VAB. And astronaut activity, including training and mission control, should be done at the launch site. So consolidate JSC into KSC. But they won't. In fact JSC has expanded since Apollo. With each expansion, moving becomes more difficult.

GW Johnson · 2015-05-30 20:25:33

In the last few posts for this thread, you guys have essentially made the case for what I proposed as a Mars mission two years ago. Build an orbit-to-orbit transport in LEO for the men, and recover it in LEO for reuse. Use it multiple times for multiple missions to multiple destinations to amortize costs.

Send separately as unmanned pre-positioned payloads to LMO, landers that are also surface habitats. These will require assembly of one type or another in LEO, and will be based initially in LMO. Use supersonic retropropulsion to land the things, once they come out of hypersonics. This will be at lower altitudes than a parachute can work, because ballistic coefficients will be nearer 300+ kg/sq.m that the 100 kg.sq.m that is max for any effectivity of chutes in that thin "air".

Make multiple landings to evaluate ISPP and ISRU techniques at multiple sites during the first half of the stay at Mars. Land everybody at the "best" site and set up a semi-permanent base that can be revisited on subsequent missions, during the second half of the stay at Mars. This works best if your lander design is single-stage and reusable for 3-30 flights (which has an inherently-lower payload fraction, so, just deal with it).

Don't count on ISPP for the return propellant, it's unproven "in field tests" until we actually go to Mars. Send the return propellant from Earth to LMO as a "suspenders-and-belt" item (there is nothing as expensive as a dead crew). Any ISPP propellant you can make, just lets you fly your landers to even more sites, suborbitally from your base site. Raises the return from the mission, if you take this approach. And, it's orders-of-magnitude better than a "semi-flag-and-footprints trip" to just one site.

So if ISPP works, you get to visit even more sites. And so get gobs more data. Our experience on Earth says no two sites are anything at all alike. Mars should follow that same trend, we have absolutely zero reason to believe otherwise. Accordingly, send enough propellant from Earth to accomplish your baseline mission (say 3 to 6 sites), even if ISPP proves completely ineffective. Send multiple landers for redundancy and rescue capability.

The diameter of the lander may require launch by SLS or something equivalent, unless we solve the engineering problem of assembly in LEO by anything more sophisticated than module docking. We have about a decade left to choose, one way or the other. There is absolutely nothing about any of the rest of such a mission that requires anything larger than an Atlas 5 to launch.

Solve a whole host of design problems with the manned orbit-to-orbit transport by using spin gravity and solar flare shielding with 15-20 cm water. Water, wastewater, and water-rich fresh or frozen food all qualify as shielding materials. GCR really isn't a killer issue, even in a peak flux year. But microgravity disease is. So supply spin gravity.

Guys, it's time to get on with the war.

GW

RobS · 2015-05-30 21:11:27

GW, I think there is a basic agreement on an architecture: a capsule and transhab-like vehicle with spin gravity for interplanetary transport, a lander of some sort, prepositioned cargo on the surface and probably in orbit. I like the idea of ISPP for production of all the propellant from the Martian surface back to Earth, but I think it is wise to bring the TEI propellant from Earth the first mission or two.

One thing I am not so sure about is multiple landings per mission, because the delta-v is quite high. Have you a way to generate numbers? Let us say you want to fly from one spot on Mars to another, 2,000 km away. That's too far for a drive. But what's the delta-v to fly that far, including retropropulsion for landing? It seems to me, it's remarkably high. If it takes 4 km per second to achieve Mars orbit, it may take 3 km/second to fly several thousand kilometers, including retropropulsion at the end. It's not easy. And how much are you hauling along with you? How many cargo landers, scattered across the surface, can you land? Do you have two such vehicles so that you have rescue capability? It seems to me it is better to choose one landing site with a wide variety of significant geological terrains within 1,000 km of the landing site, and bring along two good, reliable surface vehicles.

Robert, I agree with you that forcing NASA to spend an extra 10 or 20 billion dollars is not illegal. The government, alas, does this sort of thing all the time. But it is immoral in that it is a waste of money, and as such it is a form of government corruption. The purpose of government should be spend tax payer money wisely, not waste it. I think we can all agree that the same money could be spent more wisely within the space program than on a gigantic overexpensive booster.

I also agree with you that private companies face a major issue regarding making money off of space travel. NASA has gotten us a long way and it is now possible to imagine space hotels and space tourism in LEO, and probably, in a decade, the beginning of private research and even manufacturing in LEO. Going to Mars will be a money loser for a long time. Ideally, NASA will assign some of its budget to private enterprise accomplishing this goal. It may very well be that if Musk announces a project to take humans to Mars in, say, 2028, NASA will be shamed or publicly coerced into chipping in. Musk does not seem to be worrying much about losing money; indeed, that is why he has not made Space X publicly traded. He has said he won't do that until the Mars Colonial Transport is up and running, in fact. It appears his strategy is to fly so many rockets into LEO that he has a huge business at a much lower cost than anyone else and can generate sufficient profit to subside the Mars side of the operation.

If, in 2016, with the Dragon V-2 virtually operational, the Falcon Heavy flying, 25 successful Falcon launches in a row under his belt, and one or more Falcon first stages recovered and ready to fly again, he will have proved that he can get cargo and people to LEO much more cheaply than anyone else and that he can land stuff on the moon and Mars using superdracos. If, at that point, he says "in the next 12 years I am developing these additional items for (say) $10 billion so that I can land people on Mars in 2028, and I invite government as well as private investment," it would be very hard for NASA to ignore his proposal. Consider the embarrassment for NASA to say "sorry, we aren't interested in joining your $10 billion plan to land people on Mars in 2028 because we have our own $50 billion plan to land them there in the mid 2030s." Musk could then say "Great, my guys will have a bottle of champagne ready to welcome you." If NASA did that, I'd pray that the Canadian Space Agency took up Musk's offer instead! Why not! I think it would be very hard for the politicians to stop Musk and hard for them to refuse cooperation with him. If he added an intermediate destination--the lunar surface in 2023, perhaps--he wouldn't even be going against the official NASA plan to aim for Mars, and he might be able to get money and support for his Mars plans that way.

RobertDyck · 2015-05-30 22:17:29

GW, thank you for joining in. I am disappointed by a couple of your comments. First, Apollo demonstrated how to test technology. You don't do it with multiple LMs landed unmanned on the Moon. They landed Surveyor 1, just one. This demonstrated landing technology. NASA has already demonstrated landing technology with Viking landers 1 & 2, Pathfinder, Spirit/Opportunity, Phoenix, and Curiosity. Apollo 9 was a test of the CSM & LM in Earth orbit. Apollo 10 was a "dress rehearsal" with the LM, a low flyby and test of the LM abort-to-orbit. That was followed by the Apollo 11 landing. Apollo 8 was supposed to be an unmanned flyby of the Moon, demonstrating free return and proving the CSM can survive the trip. Sending crew was a highly risky stunt, done because the Soviets were preparing a single cosmonaut Soyuz launched on Proton to do that. We need to land a Mars sample return mission as technology demonstrator for ISPP. Again, just one. We will need to test the equipment in Earth orbit. We will need one unmanned launch of the hab to Mars orbit and back. And the ERV or MAV will be sent ahead unmanned, with sensors to determine if propellant tanks are full. That will prove ISPP for each and every mission before crew leave Earth. This does not require multiple tests, all the same.

And most importantly: DON'T EVER EVEN THINK OF SENDING RETURN PROPELLANT FROM EARTH. That will kill the mission. GW, you have said there's nothing more expensive than dead crew. There's one thing that does rival that: a mission that's cancelled before it launches.

Mars sample return missions are an example of what happens with ISPP. Someone proposes a Mars sample return mission with ISPP. Cost estimates show it's a discovery class mission, but is affordable. It gets approval, and work begins. Then someone complains that they don't want "unproven" technology on "their" mission. ISPP gets removed, replaced with return propellant hauled from Earth. That causes the cost to skyrocket; typically total mission cost triples. That cost increase causes the mission to be cancelled. It's dead until someone else notices ISPP, and how it can keep cost down. Then the whole cycle repeats. This has happened 3 times that I know of, and probably more. You would think a scientists with lots of letters behind his/her name would be able to learn. The lesson is: ISPP = mission happens. Lack of ISPP = mission cancelled.

I attended the 4th & 5th Space Exploration Workshops hosted by the Canadian Space Agency. The purpose was to establish priorities for the agency. I saw scientists treat engineers as if they're janitors. And pure research scientists treat applied scientists as if they're college drop-outs. Very cliquish, very prejudiced. You would think they would know better, but they don't. Space exploration requires new equipment, so they can't leave out everything that hasn't flown before. There's a first time for everything. ISPP is absolutely necessary for any Mars sample return mission, as we've seen by past attempts. If you want a Mars sample, don't even think of removing ISPP.

But I've also heard the opposite. People who want a human mission argue against robotic sample return. But we need to demonstrate ISPP before we commit human lives to it. Robotic sample return is the best way to do that. You would think this the perfect way to get the human and robotic space communities to work together, the conclusion is the same either way. But the two communities adamantly refuse to cooperate. And the result is we get nothing. *NOTHING*

GW Johnson · 2015-05-31 09:19:28

I tell you what, let me temper my comment about ISPP return propellant. There's not just one technology for that. Just as there are multiple ISRU technologies for base support. They don't all use the same resources, and they work in different ways at different production rates. So the downside is that there's not just one demonstration on a single mission there, there's a demo needed for each different technology.

Something that uses only the local "air" will operate the same at every site, yes. But, production rates for any given machinery size and mass will be quite slow, simply because the density of the resource is so very low. That is the sort of thing you must pre-land years ahead, and let it slowly build up supplies. That saves immense amounts of return mass, except that you have to use a lot of it accelerate the rest through about 3.6-4.0 km/s just to get it to LMO. And you need precision landing capability. There's always downsides, that's just Murphy's Law.

Something that uses soils of a particular type, or buried ice deposits, is not going to operate the in the same way at every site, simply because those resources will be of different character and properties at every site, just like here. A demo might "prove" the technology, but nothing will ever "prove" useful resources at any given site, until you actually go there and investigate. Even today, ground truth is still significantly different from remote-sensing estimates. That's also Murphy's Law.

The other thing that impacts this is the blind stupidity and rampant corruption of governments. To me, Murphy's Law says there will be one (and only one) manned expedition to Mars financed by government(s). That's where the bottom line really drives things the worst. Any other subsequent missions will be private, and unless that first mission can identify something really useful to base self-support, they'll be a long time coming. Decades to a century, maybe.

That first mission had better not be a one landing site flag-and-footprints stunt. If it is, we won't learn enough about base self-support to attract those subsequent private missions for many, many years.

If we're talking pre-landed cargo and equipment, we'd better get on with demonstrating radar homing-assisted precision landings on one of these probe missions. None so far have ever done that. That Apollo that landed near the Surveyor was no demonstration of the capability I refer to; they were just lucky they didn't miss. I'm talking about radar homing beacons and hitting a specific landing ellipse on the order of 100 m long located no more than 100 m away from the assets you pre-landed. And maybe more than once. In other words, designate, and then hit, a specific landing "pad". We're not there yet.

We'd better also get on with solving the EDL problem with high-ballistic coefficient items, where chutes are ineffective at best. Maybe the new inflatable technologies will solve that, and maybe not. Experimental test items are certainly not ready for application, especially if lives are at stake. There's a lot of years of development left to do on them. Spacex's retropropulsion approaches are technologically much further along.

GW

RobS · 2015-05-31 10:00:09

GW, I think with zeolite adsorption we have already determined there's probably a good way to extract CO2 from the atmosphere; there was quite a discussion about this a year or so ago. If you bring hydrogen along, you only need to do the ISRU that Zubrin demonstrated. We definitely need to do a demonstration mission, but that can be outlined and defined pretty well. Drilling for water is a phase 2 type task, after a base had been established.

But I still want to understand your plan. Are you talking about one mission that involves, say, 5 cargo landers at 5 different sites, each with sufficient propellant to take a small passenger to the next one, or back to orbit? If back to orbit, are you stationing a fuel depot in LMO to refuel the lander each time? That's a pretty complicated and expensive plan; too complicated for the first mission to Mars. People will want to start fairly small and simple. They won't want to start with something complex. it seems to me a plan like that is dead before it starts.

It's more likely that an Apollo-style program will be set up to do, say, 5 missions to Mars over 11 years. The first 2 or 3 will definitely happen, but after that you have to worry about cutbacks or elimination of the later missions. The way you argue against that is to point out that each mission gets a bit cheaper because you're building up assets on the surface and therefore the mass per astronaut gets less each mission. You also allow different nations bid for seats. The third mission might have only one American because the other crew come from Brazil, Canada, India, Korea, and Indonesia. That sort of thing.

RobertDyck · 2015-05-31 10:00:43

My comments were strongly worded, but I'm quite frustrated. NASA promised a human mission to Mars would depart Earth in 1981. We got a Space Shuttle instead. That was nice, but not a mission to Mars. Then President George H. W. Bush made his announcement in 1989. NASA asked for everything under the sun, with a price tag Congress would not approve. That killed that. Since we've seen various obstacles, and estimates for Mars keep moving farther into the future. I want to see it in my lifetime. I watched the last 2 missions of Mercury live as they happened, on TV. I watched the entire space program since. I'm beginning to feel I won't see a human mission to Mars in my life.

Yes, Robert Zubrin's idea for ISPP uses local air only. Nothing more. Production is quite slow, but it's finished before astronauts leave Earth. That's the beauty of his system. One reason I want to keep that design in any updated mission plan. Because ERV or MAV propellant tanks are verified before astronauts leave Earth, you don't need anything more than one demonstrator. Some people have argued for using Mars permafrost or ground ice as source material for ISPP. But that has all the issues you raise. I argue for Robert Zubrin's system because it uses just air, which is the same across the planet, so only one unmanned demonstrator is needed. And it's simpler. No digging or melting or filtering, just an atmosphere inlet.

You keep raising retropropulsion. I'm not convinced it's necessary. I cited a study by the ADEPT team that showed parachutes still are the lowest total launch mass. And they do work. With large mass, the size of a Mars Direct ERV or Hab. Two catches to doing that: first aerocapture into Mars orbit, then land. Don't use direct entry. If you try direct entry with a large mass, then you get the problems you talk about. Second, a simple aeroshell is not good enough. It doesn't "catch enough air" so doesn't decelerate enough. Again, same problems you talk about. The solution is an umbrella style heat shield that does catch enough air to slow sufficiently, at high enough altitude, that parachutes can work. They calculated that a 23 metre diameter umbrella heat shield is necessary for the mass of a Mars Direct ERV or Hab. Note: the presentation Robert Zubrin and David Baker made in June 1990 included an umbrella heat shield with carbon fibre fabric, and was 23 metre diameter. Same material, same size, image that! And in the book "The Case For Mars", Robert Zubrin said David Baker designed that part. Let's give credit where credit is due, David Baker came up with a great design.

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