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#51 2012-05-31 15:46:16

Impaler
Member
From: South Hill, Virginia
Registered: 2012-05-14
Posts: 286

Re: Mars Semi-Direct with Falcon

All the Zubrin and NASA numbers on Mars EDL are BS, they are an order of magnitude larger and more efficient they anything that's ever been achieved to data, The Curiosity Lander delivered ~25% of its Entry mass as payload and that payload mass of 1 ton was the limit of our current technology.  Their is so much more development to do here it's hardly worth designing missions around specific landing numbers, stick to the known areas of interplanetary thrust in vacuum or assent from planetary surfaces.

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#52 2012-05-31 17:54:23

GW Johnson
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From: McGregor, Texas USA
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Posts: 5,609
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Re: Mars Semi-Direct with Falcon

Viking was big and heavy and nothing but rocket braking to landing,  all the way from the end of atmospheric entry.  I don't see why that can't be scaled up to any size.  Might not be the lowest propellant mass,  but we already know it worked twice in a row back in 1976. 

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#53 2012-05-31 18:07:08

louis
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From: UK
Registered: 2008-03-24
Posts: 7,208

Re: Mars Semi-Direct with Falcon

GW Johnson wrote:

Viking was big and heavy and nothing but rocket braking to landing,  all the way from the end of atmospheric entry.  I don't see why that can't be scaled up to any size.  Might not be the lowest propellant mass,  but we already know it worked twice in a row back in 1976. 

GW

I'm pleased to read that from you GW, as a rocket man, since that has always been my hunch.  It's the simplest, safest way to do it...


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#54 2012-05-31 20:54:51

RobS
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Re: Mars Semi-Direct with Falcon

GW Johnson wrote:

Viking was big and heavy and nothing but rocket braking to landing,  all the way from the end of atmospheric entry.  I don't see why that can't be scaled up to any size.  Might not be the lowest propellant mass,  but we already know it worked twice in a row back in 1976. 

GW

I don't know what you mean here, G.W. Johnson. Viking first used a heat shield, then parachutes, then rockets for the terminal delta-v of several hundred miles per hour. 90-95% of the braking was atmospheric. I know; I was in the science control room, that night. The problem with scaling up Viking's system is quite simple; it had a big heat shield, say 4 or 5 feet across (15 to 20 square feet) and a total entry mass of maybe half a ton or a ton, so the mass per square foot of heat shield was in the range of 100 lbs per square foot. A manned vehicle (and a cargo vehicle to support a crew) is going to mass quite a lot more and the heat shield can't easily be made to be huge, nor can the parachutes easily be scaled up, so the mass per square foot of heat shield and per square foot of parachute will be a lot more. This is a problem with a thin atmosphere; you will hit the ground before the air has slowed you down. So you have to do more rocket braking. But with a really big vehicle would need to start firing its engines while it is still hypersonic, and that hasn't been tested yet. This is presumably a solvable problem, but no one has yet thrown enough money at it to find the solution.

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#55 2012-05-31 23:36:01

Impaler
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From: South Hill, Virginia
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Posts: 286

Re: Mars Semi-Direct with Falcon

I don't think the Payload-mass / Entry-mass ratio of Viking was much different from the 25% of Curiosity as they basically identical EDL system (Anyone have hard numbers?).  Their has been NO ADVANCEMENT in Martian EDL in the last 36 years.  Their may be some great potential for lighter heat shields and Balutes but I don't think anything better then 50% is achievable with any method currently know or proposed.

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#56 2012-06-01 06:04:33

Rune
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From: Madrid, Spain
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Posts: 191

Re: Mars Semi-Direct with Falcon

Yup, except the crane part, MSL's EDL is pretty much the same as Viking's. Which makes sense, since they are approximately of the same order of magnitude in mass, and it is a "tried and true" landing system. Try to combine 3 separate landing systems in under one ton, and you are bound to use a lot of the space. Add to that the cruising systems, and you get to the ridiculously low 25% landed useful mass of the unmanned probes to date. This is, in part, for the same reason rockets get more efficient with size: scaling things is rarely linear.

However, any manned payload is going to be a very different thing form the tiny rovers and landers to date. For ballistic coefficient reasons, like RobS implies, parachutes are definitively not an efficient option anymore. In fact, they are not efficient at all even with the small ballistic coefficient of the vikings, but supersonic rocket ignition has always been regarded as unproven and dangerous, so it has never actually been developed. Last I heard, it is a problem that sounds much worse than it is, but it is still an unsolved problem.

You could decrease again the ballistic coefficient by other means: ballutes, inflatable heatshields, parashields (similar to inflatable, but with a rigid extensible backbone), whatever. The nice thing of these undeveloped systems is that they are supposed to be lighter than a traditional heatshield (well, except maybe ballutes, 'cause those don't replace the heatshield), so for big payloads I am reasonably sure you can get them to be a reasonable fraction of total payload. Much like heatshields designed for earth, and entirely within Zubrin's assumptions of about 15% of the entry mass. They would need testing and development, though. Nothing guarantees some unknown ends up disqualifying one or more of these approaches, but I expect some method is actually doable. Seems like a nice thing for NASA to determine with their huge budget and fancy installations, if they ever get around to actually do it. This problem is not exactly new, you know.

Or, you could expand the job of the retros. No way you can get around developing supersonic retros if you want to land on Mars, parachutes look ridiculously big for anything other than tiny probes. So since you are going to have to use engines, why not go the extra mile and figure out how to reliably turn them on while hypersonic, not just supersonic, and the requirement for ballistic coefficient gets substantially relaxed (and the fraction of fuel required grows, of course).

All in all, for big >10mT payloads that are delivered to LMO by some other (reusable, I expect) orbit to orbit "cruise" stage, I expect the landed mass to be well over 50% of the entry mass. After all, the exponential part of the rocket equation works beautifully in your favor when you are asking much less than your exhaust speed of your propulsion system, as would be the case here (<1000m/s?).


Rune. Fun fact: any payload landed like this could hop around if refueled. So any ISRU plant is mobile by nature.


In the beginning the universe was created. This has made a lot of people very angry and been widely regarded as a "bad move"

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#57 2012-06-01 06:19:51

RGClark
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Re: Mars Semi-Direct with Falcon

louis wrote:

I've alwayus reckoned on getting something like 200 tonnes to orbit, so 4 Falcon Heavies, so you get 44 tonnes to the surface.  There might be a requirement for smaller supply missions, landing robotic craft. So we might have more than four launchs. But 200 tonnes to LEO is "only" $1billion at $5000 per kg - and will likely be far less in 10 years' time. That's a very reasonable "platform" on which to build a mission costing somewhere between $10billion and $20 billion over ten years - max. $2 billion per annum.

SpaceX has said they expect to charge in the range of $100 million per launch for the Falcon Heavy, so around $400 million for four, and the first test launch is supposed to take place next year.


  Bob Clark


Old Space rule of acquisition (with a nod to Star Trek - the Next Generation):

      “Anything worth doing is worth doing for a billion dollars.”

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#58 2012-06-01 07:01:23

Rune
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Posts: 191

Re: Mars Semi-Direct with Falcon

RGClark wrote:
louis wrote:

I've alwayus reckoned on getting something like 200 tonnes to orbit, so 4 Falcon Heavies, so you get 44 tonnes to the surface.  There might be a requirement for smaller supply missions, landing robotic craft. So we might have more than four launchs. But 200 tonnes to LEO is "only" $1billion at $5000 per kg - and will likely be far less in 10 years' time. That's a very reasonable "platform" on which to build a mission costing somewhere between $10billion and $20 billion over ten years - max. $2 billion per annum.

SpaceX has said they expect to charge in the range of $100 million per launch for the Falcon Heavy, so around $400 million for four, and the first test launch is supposed to take place next year.


  Bob Clark

$128 million if you load the falcon to the rim (>6.4mT to GTO), $80 million if you launch smaller loads, as of today (so I'd say Intelsat will pay about $80 million in the end). I seriously doubt Falcon Heavy ends up being used to launch 50mT payloads to LEO. Much more likely, it will launch smaller payloads farther. Also, I'm about 50% sure a ~25mT Raptor upper stage ends up being developed to take ~Salyut sized crew modules to... anywhere. The plain version can take Dragons (unmanned or not) for resupply to the same locations. Bonus points if the Raptor becomes reusable. I don't know who musk would get to pay for all of this, of course, but it is the path I would take.


Rune. BA330 is a ~Salyut module, in my book. A bit fancier, but the same thing in the end.


In the beginning the universe was created. This has made a lot of people very angry and been widely regarded as a "bad move"

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#59 2012-06-02 18:56:43

Impaler
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From: South Hill, Virginia
Registered: 2012-05-14
Posts: 286

Re: Mars Semi-Direct with Falcon

While a BA330 masses in the 20 ton range like a Salut/Zarya/Zvezda (any Russian Proton launched Module really) its radically different in the sense that it is an empty shell with virtually no hardware inside it other then basic orbital maneuvering and solar power.  Those Russian modules have 70-90 cubic meter pressurized volume (with half of it occupied by equipment), but all that equipment between two such modules provide a full suite of whats needed to have a permanently manned station.  A BA330 is going to need a minimum of 10 additional tons of equipment to be installed in it (which is a great thing cause it can be modular and replaceable) before it becomes a viable long term habitat.

If you had a 50 mt launch vehicle I'd have the Ruskis make a 'Salut on Steroids' combining the capabilities of Zarya, Zvenzda and Node1 (combined about 50 ton).  With that mass it should be possible to get orbital maneuvering, 6 crew life-support system, EVA airlocks, integrated robotic arm and at-least 10 docking/berthing ports all along its length and on the ends.  Then attach what ever size inflatables you can manage to launch along with some disposable tin-can MPLM full of equipment to it and presto a fast and easy to assemble space station/hotel.

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#60 2012-06-03 11:32:06

GW Johnson
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Re: Mars Semi-Direct with Falcon

RobS was right about Viking somewhere above.  I had completely forgotten the chutes it used.  Sorry. 

The trouble with Mars is there's not enough density for the chutes to decelerate you very much,  before you're on the ground.  But some combined scheme of aero decelerator-plus-rocket braking might be a possible answer.  We've never really done those two together.  And there are serious problems with that concept,  I know. 

The other problem with chutes is that there seems to be a limit to how big a payload can be practically supported by chutes,  even here at home.  I've never seen more than 3 chutes at once in a cluster,  or a payload bigger than an Apollo or a Dragon.  It's worse on Mars by the density ratio/0.38. 

The Russians used a combination of chute plus last-second rocket braking to land army tanks (no persons aboard) dropped from airplanes,  some time about 5 decades ago.  I'm not sure the density on Mars would make that approach practical,  given the dynamical troubles of chute plus rocket simultaneously,  and the low density.  Probably not worth the trouble.  It barely worked for the Russians here.  But it's an idea.

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#61 2013-04-06 07:29:23

StarDreamer
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From: Ontario, Canada
Registered: 2007-04-28
Posts: 92

Re: Mars Semi-Direct with Falcon

I've been away from these forums for a few years and see I missed some really good threads. I'd like to reinvigorate this one if others are interested. I am quoting RobS plan here, but I also was paying heed to GW's comments about career-limit radiation and the problems of getting good exploration accomplished.

At this date, we still do not know enough about Mars for a manned mission to achieve what it could achieve. Sure, we have the tech to get ppl to Mars, but we do not yet have the knowledge of Mars itself or experience on Mars to make it work as well as it might. I would like to see the success of Curiosity and Opportunity replicated about 50-100 times over before we send ppl there. The ISS was a global effort. This can be a global effort as well. We can put 100 rovers on Mars for less than $50B. (Versus the price of propping up one failed bank corporation for .... you dont want to know how much!) We should be aiming 20 rovers at Mars at each launch window over the next decade. Let them crawl all over the planet, checking out as much as possible and gathering rocks and samples. Try ballooning over Mars with black sun-inflated balloons. With each Rover payload, send along some iffier proposals to see how they work. Send along too a little bit of infrastructure for the future crewed mission to retrieve and use. Nothing ventured, nothing gained.

When we DO get a manned expedition to Mars, they should go in knowing what to expect and have lots of work laid out for them in advance by the Rovers. Part of their mission should be to visit each of the 100 rovers that got there before them and collect the physical data from them, like rocks and gasses, etc. They should arirve with replacement parts for the Rovers and go in expectation of doing service maintenance on all of them so that the Rovers can continue working for another decade on Mars before the next manned mission arrives. If we can get something to Mars with the crew that's capable of lifting cargo across the Martian surface, by flight, then they could also pick up errant Rovers or dead-ended Rovers and relocate them to new territory -- shuffle our whole deck of 100 up there. We could devise a modular aerodynamic lifter of some kind which could be attached to a Rover, so that it gives the Rover wings and the Rover gives it wheels. Flying over the rough terrain makes the most sense, if we can figure out how.

In short, GW and RobS make me realise just how much more homework there is to do that we havent done yet, but could do without risking human life for a mission which would be more politics and showmanship (flags and footprints) than science.

RobS wrote:

Thank you, GW Johnson, I very much like and agree with your post. I wonder what the implications of it are.

1. How many to send to Mars. I'd favor six, if it is practical, perhaps two ships of three each. If either one had difficulties, the other one could provide for everyone, especially if parts could be salvaged from the incapacitated vehicle. When the International Space Station had only 3 on board it could do very little because it took 2 crew full time to maintain the station! I suspect a Mars base would take one or two as well, so you need a minimum of three and preferably more.

2. Establishing a series of beachheads (one every 26 months) versus establishing a "Martian McMurdo." McMurdo, of course, is the hub of Antarctic operations, and having a well equipped hub has been invaluable for Antarctic exploration (which is about 5% the size of Mars!). I think safety favors a concentration of resources at one point initially, but that also reduces the range of exploration you do at first. A McMurdo can also accumulate habs so that there is a lot of pressurized volume per crewmember.

3. Practical range of a human crew. I refer to their surface vehicles here. Zubrin proposes a pressurized rover with a range of 1,000 kilometers, but I don't think anyone is going 400+ kilometers out and back until Mars has at least two such vehicles and probably has a surface crew of more than six, for safety reasons.

4. Human/robot interaction. If we had five or six telerobotic operated vehicles (TROVs) like a second-generation Spirit and Opportunity or like the Mars Science Lab, a surface crew could supplement a terrestrial crew quite nicely because they could control the vehicles live. If each TROV had a sample bin that could eventually be retrieved, that would be even better. In my Mars novel I envisioned robotic solar powered airplanes called "Sunwings" rather like the Helios that NASA experiemented with a few years back. The astronauts would assemble the pieces of the sunwing and test the vehicles. They could be flown down to a TROV robotically and snag a long mast with a hook. The mast was attached to the sample bin, thereby retrieving the samples and bringing them back to base, where some preliminary analysis could be done. Some samples could be selected for return to earth later. There may be other ways to retrieve samples, too; Zubrin proposed a vehicle with a built in thermal rocket. The solar power on the wings would heat up a beryllium engine and a pump would compress carbon dioxide from the atmosphere. Once the engine was hot and the CO2 tank full, the vehicle would run the CO2 through the hot beryllium engine and fly using the rocket exhaust perhaps 20 or 50 kilometers. It would then perform a rocket landing, examine rocks, recharge its propulsion system, and repeat. A balloon/TROV system might work as well. The idea would be to keep the crew busy inside the base with vital tasks spread out all over Mars.

5. Longer term, exploration expands via a transportation system of some kind. Maybe once there are a dozen people on Mars and considerable experience with vehicles has been accumulated, you send out expeditions to clear a track to an attractive geological site about 500 kilometers away, where you set up a small "oasis" (solar panels, Sabatier reactor, water supply, maybe a well, methane and oxygen tanks, maybe some emergency shelter and supplies). You return to base, process your samples, write up articles for Nature and JGR with a terrestrial support crew, then a few months later you go out with the equipment for a second oasis. You stop at the first oasis to refuel and do a bit a maintenance and set up a second oasis another 500 kilometers out. Perhaps sunwings drop ice blocks wrapped in plastic so you have a water supply at each one. A system like this could gradually develop a network of dirt tracks across the planet. Or perhaps larger sunwings can safely carry people and the expedition equipment can be kept out almost permanently, with crew rotation by air. But exploration strategies like this have to evolve over time as equipment improves. It may be a few people and a lot of robots will be plenty.


[color=darkred][b]~~Bryan[/b][/color]

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#62 2013-04-06 08:56:16

RobS
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Re: Mars Semi-Direct with Falcon

Dear Bryan/Star Dreamer:

Personally, I think the balance lies somewhere in between. We need more unmanned vehicles on Mars, but I don't think we need to send 100 of them before we send humans. A human crew can accomplish a huge amount. What we need is to explore a few more potential landing sites and choose one for the first human landing. Personally, I really like Mount Sharp, but there are other spots that have a huge amount of geology, such as the eastern end of Valles Marineris, where one could head north into Chryse, south into chaos, and west into the deepest canyon in the solar system. We may first need a new generation of remote sensing, because we want to land somewhere near the equator with water not too far underground. If we find thermal imaging suggestive of geothermal power (maybe Elysium?), that would be a possible site, too. In fifteen years, with more remote sensing and maybe 1 or 2 Mars sample returns, we'd be in good shape to send people.

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#63 2013-04-06 09:24:42

StarDreamer
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From: Ontario, Canada
Registered: 2007-04-28
Posts: 92

Re: Mars Semi-Direct with Falcon

In fifteen years, we could have somewhere between 50 and 100 rovers on Mars, with no drag on your timeline for human missions.
It's all in how much effort we as a species want to put into this. It CAN be done. It's just politics and willpower that stand in our way.


[color=darkred][b]~~Bryan[/b][/color]

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#64 2013-04-06 10:01:45

Terraformer
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Re: Mars Semi-Direct with Falcon

There's lots we could do as a species with our resources. We could move our entire population to space within the next couple of decades if we were willing to put all our resources into it. There's about 7 billion of us here, and maybe 2 billion of us live in countries where we have high disposable incomes. If we spent $1000 for each of those 2 billion people on colonising space, we could have a significant cis-Lunar infrastructure within a decade, and have mapped Mars with robotic and human crews, and have nuclear powered spacecraft at each of the giant planets, and have a large fleet of thousands of shuttles, each capable of taking 200 people into orbit and making that trip 300 times a year....


Use what is abundant and build to last

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#65 2013-04-06 10:34:05

StarDreamer
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From: Ontario, Canada
Registered: 2007-04-28
Posts: 92

Re: Mars Semi-Direct with Falcon

Not even $2T could accomplish all that. And a good chunk of European, Americans and Chinese do NOT have $1k extra to devote to this. But there's maybe 1% in each of those regions who have $1M or more.


[color=darkred][b]~~Bryan[/b][/color]

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#66 2013-04-06 10:44:00

RobS
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Re: Mars Semi-Direct with Falcon

Dear Bryan: I agree it's possible, but it won't happen. The people who want a rover on Europa will lobby against 100 on Mars because they'll want a piece of the pie. The people who want humans on Mars will be afraid governments will stick to rovers and lobby against it. The plan is out of scale with everything else, so it'll never get approved by anyone. And there are valid arguments against sending so many rovers before you send humans; it is excessive by most standards.

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#67 2013-04-06 11:03:29

StarDreamer
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From: Ontario, Canada
Registered: 2007-04-28
Posts: 92

Re: Mars Semi-Direct with Falcon

RobS wrote:

Dear Bryan: I agree it's possible, but it won't happen. The people who want a rover on Europa will lobby against 100 on Mars because they'll want a piece of the pie. The people who want humans on Mars will be afraid governments will stick to rovers and lobby against it. The plan is out of scale with everything else, so it'll never get approved by anyone. And there are valid arguments against sending so many rovers before you send humans; it is excessive by most standards.

But someday, when we have a colony ON Mars, 1000 rovers shall be too few.....

I understand how the politics goes. If we could get the willpower to set a budget in the $100B-$300B range and higher, then there'd be so much money to go around that the fear of being marginalised might step down a rung or two.

And I just pulled the 100 number out of thin air. The point was that, as GW said, you end up with a flags and footprints manned mission if you dont lay enough groundwork first, which means exploration and knowing what resources are where. Knowledge is power. If we dont get past being timorously inquisitive to being methodically investigative, manned missions will not accomplish much more than flags and footprints and, worse, perhaps kill the people we propose to send.


[color=darkred][b]~~Bryan[/b][/color]

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#68 2013-04-06 12:09:28

GW Johnson
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From: McGregor, Texas USA
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Posts: 5,609
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Re: Mars Semi-Direct with Falcon

Well,  there's a sort of practical trade-off between a massive rover program and a very small one,  before a manned expedition goes to Mars.  There are things men do best in the search for resources and other "ground truth",  things robots and remotely-operated devices can never do.  One is drill very deep.  Another is adapt quickly to the unexpected. 

We're going to need all of that. It not really a choice of either manned or unmanned,  it's actually both together. 

That's why I tend to say (repeatedly,  I know,  sorry) the first manned expedition needs to do an enormous amount of "real exploration" at multiple sites on that very first voyage,  just like they did on the first voyages to the New World 500 years ago.  And yes,  on Mars they should also do some field trials of ISRU and life support and other settlement-enabling technologies while there on those first landings. 

I would defer the betting of the crew's lives on those new-technology things to the next mission,  when the field trials verdicts are actually in.  It's just a common-sense thing with me.  Not everyone sees it that way,  and I understand that.  But I am pretty sure that I'm right about that issue.  If we try to fly some of these minimalist designs I've seen touted,  we're going to kill the crew,  most likely outcome,  and quite probably before they can even land.

As for when to go, it's just a matter of expense.  The right mission design I believe to be staging from LEO to LMO,  with reusable landers at Mars.  We could put together the hardware to carry this off within a decade from now,  with the chemical propulsion and commercial launch rockets we have today (or within 5 years,  counting Falcon-Heavy).  It's just hugely expensive.  Maybe $1-300B.  Depending upon who does it and how. 

Some sort of "hotter" propulsion,  such as atomic rockets,  just reduces assembled mass in LEO and thus mission expense.  I think NTR could cut it by a factor of 2-4,  but others disagree.  It's just a trade-off.  If you wait around longer than anyone wants to wait,  you can pay a lot less.  That's as true now as it was 500 years ago.  Ship technology,  primarily propulsion,  is the cost driver.  Always will be.

I keep asking the question "what could be available in 5-10 years so we could go in 10-15 years?",  followed by the related question "why are we not funding these developments?"  SLS is not "hotter propulsion",  it's just a bigger rocket.  And because it's a government design with no real forseeable commercial application,  it will never be as cheap to launch as the commercial rockets.  Yet SLS will come to dominate NASA's budget.  All of their flagship projects have done that,  since 1958.

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

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#69 2013-04-06 14:06:57

Terraformer
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Re: Mars Semi-Direct with Falcon

StarDreamer wrote:

Not even $2T could accomplish all that. And a good chunk of European, Americans and Chinese do NOT have $1k extra to devote to this. But there's maybe 1% in each of those regions who have $1M or more.

The median income in the UK is £26k. $1000 dollars a year represents about £650 from that. Someone on such an income will be taxed £3.2k a year on their income, not counting additional taxes, and about half the population work. To further put that into perspective, Sky TV costs £480 a year. Housing is the single biggest cost for people; if we can slash this down by £1-200 a month (say, by loosening planning restrictions... but that's Terran politics), then the people will have more money to spend on a space program. That's not counting all the richer people who have much more disposable income. Anyway, my point is that the money is there if the people want to spend it on such a program.

As to what we could accomplish with this... I think you seriously underestimate what we could achieve on this budget. NASA - and this is NASA we're talking about here - came up with a cost of $450 billion for a plan that involved extensive lunar infrastructure. Even accounting for inflation, I'm talking about a budget maybe 3 times that. Getting a self-sustaining lunar infrastructure would cost, at most, about 1% of our yearly budget (which would be greater than NASA gets at the moment...). Intense R&D to develop the shuttles that would bring the cost of reaching orbit to a few grand per person wouldn't take up much more as a fraction, and we'd have plenty to devote to developing more effective rockets. As well as to setting up colony seeds on many of our planets, and building the infrastructure to settle them.

The key is exponential growth once in space. Clanking replicators, I believe they're called... nothing wrong with having humans in the loop.


Use what is abundant and build to last

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#70 2013-04-07 01:56:09

RGClark
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From: Philadelphia, PA
Registered: 2006-07-05
Posts: 744
Website

Re: Mars Semi-Direct with Falcon

StarDreamer wrote:

I've been away from these forums for a few years and see I missed some really good threads. I'd like to reinvigorate this one if others are interested.

Welcome back to the forum.

   Bob Clark


Old Space rule of acquisition (with a nod to Star Trek - the Next Generation):

      “Anything worth doing is worth doing for a billion dollars.”

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#71 2013-04-07 04:10:51

louis
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From: UK
Registered: 2008-03-24
Posts: 7,208

Re: Mars Semi-Direct with Falcon

StarDreamer -

My view is you don't need to get to know the whole of the planet, as you seem to be suggesting. You just need to get to know one landing site very well.  I think we know enough about Mars already to select good landing sites.

Once you have your landing site, it is not - in my view - a question of trying to ship everything over in one go.  There should be maybe 8 pre-landings by robot craft taking in maybe 3 tonne loads. These would then assure your basic food, water, power and habitat supplies are all in place before the crew even leave Earth. You can even, in theory, being manufacturing rocket fuel for a return to Earth but for Mission One you might be landing rocket fuel as well.

Having landed so many supplies, one should then be able to reduce the human lander to a minimal load.


StarDreamer wrote:

I've been away from these forums for a few years and see I missed some really good threads. I'd like to reinvigorate this one if others are interested. I am quoting RobS plan here, but I also was paying heed to GW's comments about career-limit radiation and the problems of getting good exploration accomplished.

At this date, we still do not know enough about Mars for a manned mission to achieve what it could achieve. Sure, we have the tech to get ppl to Mars, but we do not yet have the knowledge of Mars itself or experience on Mars to make it work as well as it might. I would like to see the success of Curiosity and Opportunity replicated about 50-100 times over before we send ppl there. The ISS was a global effort. This can be a global effort as well. We can put 100 rovers on Mars for less than $50B. (Versus the price of propping up one failed bank corporation for .... you dont want to know how much!) We should be aiming 20 rovers at Mars at each launch window over the next decade. Let them crawl all over the planet, checking out as much as possible and gathering rocks and samples. Try ballooning over Mars with black sun-inflated balloons. With each Rover payload, send along some iffier proposals to see how they work. Send along too a little bit of infrastructure for the future crewed mission to retrieve and use. Nothing ventured, nothing gained.

When we DO get a manned expedition to Mars, they should go in knowing what to expect and have lots of work laid out for them in advance by the Rovers. Part of their mission should be to visit each of the 100 rovers that got there before them and collect the physical data from them, like rocks and gasses, etc. They should arirve with replacement parts for the Rovers and go in expectation of doing service maintenance on all of them so that the Rovers can continue working for another decade on Mars before the next manned mission arrives. If we can get something to Mars with the crew that's capable of lifting cargo across the Martian surface, by flight, then they could also pick up errant Rovers or dead-ended Rovers and relocate them to new territory -- shuffle our whole deck of 100 up there. We could devise a modular aerodynamic lifter of some kind which could be attached to a Rover, so that it gives the Rover wings and the Rover gives it wheels. Flying over the rough terrain makes the most sense, if we can figure out how.

In short, GW and RobS make me realise just how much more homework there is to do that we havent done yet, but could do without risking human life for a mission which would be more politics and showmanship (flags and footprints) than science.

RobS wrote:

Thank you, GW Johnson, I very much like and agree with your post. I wonder what the implications of it are.

1. How many to send to Mars. I'd favor six, if it is practical, perhaps two ships of three each. If either one had difficulties, the other one could provide for everyone, especially if parts could be salvaged from the incapacitated vehicle. When the International Space Station had only 3 on board it could do very little because it took 2 crew full time to maintain the station! I suspect a Mars base would take one or two as well, so you need a minimum of three and preferably more.

2. Establishing a series of beachheads (one every 26 months) versus establishing a "Martian McMurdo." McMurdo, of course, is the hub of Antarctic operations, and having a well equipped hub has been invaluable for Antarctic exploration (which is about 5% the size of Mars!). I think safety favors a concentration of resources at one point initially, but that also reduces the range of exploration you do at first. A McMurdo can also accumulate habs so that there is a lot of pressurized volume per crewmember.

3. Practical range of a human crew. I refer to their surface vehicles here. Zubrin proposes a pressurized rover with a range of 1,000 kilometers, but I don't think anyone is going 400+ kilometers out and back until Mars has at least two such vehicles and probably has a surface crew of more than six, for safety reasons.

4. Human/robot interaction. If we had five or six telerobotic operated vehicles (TROVs) like a second-generation Spirit and Opportunity or like the Mars Science Lab, a surface crew could supplement a terrestrial crew quite nicely because they could control the vehicles live. If each TROV had a sample bin that could eventually be retrieved, that would be even better. In my Mars novel I envisioned robotic solar powered airplanes called "Sunwings" rather like the Helios that NASA experiemented with a few years back. The astronauts would assemble the pieces of the sunwing and test the vehicles. They could be flown down to a TROV robotically and snag a long mast with a hook. The mast was attached to the sample bin, thereby retrieving the samples and bringing them back to base, where some preliminary analysis could be done. Some samples could be selected for return to earth later. There may be other ways to retrieve samples, too; Zubrin proposed a vehicle with a built in thermal rocket. The solar power on the wings would heat up a beryllium engine and a pump would compress carbon dioxide from the atmosphere. Once the engine was hot and the CO2 tank full, the vehicle would run the CO2 through the hot beryllium engine and fly using the rocket exhaust perhaps 20 or 50 kilometers. It would then perform a rocket landing, examine rocks, recharge its propulsion system, and repeat. A balloon/TROV system might work as well. The idea would be to keep the crew busy inside the base with vital tasks spread out all over Mars.

5. Longer term, exploration expands via a transportation system of some kind. Maybe once there are a dozen people on Mars and considerable experience with vehicles has been accumulated, you send out expeditions to clear a track to an attractive geological site about 500 kilometers away, where you set up a small "oasis" (solar panels, Sabatier reactor, water supply, maybe a well, methane and oxygen tanks, maybe some emergency shelter and supplies). You return to base, process your samples, write up articles for Nature and JGR with a terrestrial support crew, then a few months later you go out with the equipment for a second oasis. You stop at the first oasis to refuel and do a bit a maintenance and set up a second oasis another 500 kilometers out. Perhaps sunwings drop ice blocks wrapped in plastic so you have a water supply at each one. A system like this could gradually develop a network of dirt tracks across the planet. Or perhaps larger sunwings can safely carry people and the expedition equipment can be kept out almost permanently, with crew rotation by air. But exploration strategies like this have to evolve over time as equipment improves. It may be a few people and a lot of robots will be plenty.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#72 2013-04-07 08:35:58

StarDreamer
Member
From: Ontario, Canada
Registered: 2007-04-28
Posts: 92

Re: Mars Semi-Direct with Falcon

I was responding to GW's original contribution to this thread, and agreeing with it. Maybe you dont need to know the whole planet before we go there, but if you're going to drop 8 robots at the chosen landing site, well, How do you choose this landing site? From aerial photography alone or from previous exploration on the ground to get a sense of what resources are there already? And how is this exploration going to get done if we limit ourselves to 2 rovers per decade over the next 200 years ...............

I am arguing that if we really mean to send manned crew to Mars then, to make the best use of their limited time at the red planet, we need to plan for multiple landings at multiple sites, or distribute resources by robot all over the planet long in advance so that the crew can make a tour of all those previous sites in one go.

GW Johnson wrote:

I think you have to consider what you can actually accomplish with 1-3 astronauts landed (hopefully not a one-way suicide mission) at one single site on Mars,  and maybe just barely enough gear to go home.  This matters little whether the return gear is prepositioned,  locally produced, or carried with them.

Your not going to accomplish very much beyond flag-and-footprints and a couple of tow sacks of surface rocks.  Even if you have a rover,  the surface sampling will only be a few dozens of km apart.  That's basically the same model as we used with Apollo going to the moon,  and,  in hindsight,  that never really "explored" the moon. 

It's been the probes since Apollo that did what "real exploration" we actually have accomplished (on the moon and on Mars).  Exploration fundamentally answers two deceptively-simple but difficult questions:  "what all is there?" and "where exactly is it?".  A lot of the stuff we'd like to find is buried deep,  sometimes very deep.  And it is never,  ever uniformly distributed. 

I haven't seen in any of the Mars mission proposals,  even Zubrin's,  anything that addresses doing real exploration.  Not in all these years since the "battlestar galactica" concepts first dreamed up in the 1950's. 

But "real exploration" is exactly the prerequisite for siting bases,  prospecting,  and eventually establishing permanent settlements.  You cannot utilize local resources effectively until you answer those two questions.  And it is not easy to answer them.  Some can be done by robots,  some of it must be done with men.  That's just life. 

Mars is a lot farther away than the moon.  For a robot,  that's no problem,  for humans it is.  I have not seen since Skylab in the 70's a habitat spacious enough to support a mentally-healthy crew for the 2+ year round trip to Mars,  with the kind of rockets we have. 

It doesn't need to be that way.  But,  you have to give up the Apollo flag-and-footprints model,  and you have to face up to the question of safely sending healthy people all that way,  and getting them back alive.  That is not done with a minimalist approach.  It is constraint driven. 

Back to "real exploration":  it's a very long trip to Mars.  If we're going to all the trouble of sending men there,  then why not plan on more than one landing?  Really do a proper sampling all around the planet.  That's not a minimalist design,  but it need not be "battlestar galactica" either. 

And once you're past the 25 ton shuttle payload,  anything you send can be assembled in LEO from docked payloads.  It's the lowest cost per payload mass that counts.  Falcon heavy is 53 tons at $800-1000 per pound.  So who needs a gigantic launch rocket?

Just some things to think about. 

GW


[color=darkred][b]~~Bryan[/b][/color]

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