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I’m seeing some rather acrimonious discussions in multiple threads in this “human missions” topic. On the face of it, these arguments are over the feasibility or merits of this vs that technology. But what I detect underneath is the clash of incompatible (and often unrealistic) expectations regarding manned missions to Mars.
Expectations need to be both realistic and challenging. If they are not realistic, disappointment always results, because the overambitious mission will never be flown as “too impossible” or “too expensive” or both. On the other hand, if they are not challenging, then anything we do at Mars will be nothing but another “flag and footprints” stunt, which will lead to nothing, just like it did at the moon.
Both ways, nothing substantial ever gets done. So the “right” expectations lie somewhere between the minimalist “flag and footprints” stunt and the colony-on-the-first-landing. There are some real-world constraints that may help you set your own realistic expectations. My take on them follows.
One constraint is expense and difficulty at this time in our history. There’s no such thing as warp drive, fusion rockets, or other “magic” science fiction technologies, and there won’t be for many decades yet. We’re stuck with chemical rockets and weak electric thrusters, or at most a reprise of the old NERVA nuclear thermal rocket (although in today’s hysterical anti-nuclear climate, I wouldn’t hold my breath waiting for that one).
Going to Mars as a two-way trip is at least an order of magnitude tougher than was going to the moon, even though the delta-vee to trans-Mars injection is just about the same as the delta-vee to lunar orbit. The difference is round trip mission duration: about two-and-a-half years instead of a-week-and-a-half.
This duration affects everything in multiple ways, primarily by increasing the masses to be thrown to values far beyond the capability any possible single rocket imaginable. Therefore, anything we actually do will look NOTHING like Apollo. No one will EVER go to Mars on a moon rocket, except as a one-way suicide mission, and likely dead long before arrival.
Now, Apollo was originally intended to extend as far as Apollo-20, -21, or even -22. That’s 10 or 12 total landings on the moon, not counting orbit-only and rehearsals, and ignoring the fact that the program was cancelled in the middle of those landings (only 6 were ever successfully made). Mars is an order of magnitude more difficult, and the government pockets are no deeper now, than they were for Apollo then. Less deep is actually more likely.
An order of magnitude less scope to fit the not-very-deep pockets is EXACTLY why there will be one (and ONLY ONE!) government-funded manned mission to Mars! This is based on the history of Apollo, and the rather unpleasant little fact of life that governments ever since have proven too stingy to support going back to the moon, much less to Mars.
That being the most likely shape of (government-funded) things to come, those who want to take things one small step at a time in multiple sequential missions to Mars suffer from VERY unrealistic expectations about there being multiple sequential missions. That being the case, what is the point of going to all that trouble to send men to Mars orbit but not land? Especially since by spending those resources to do that orbital mission, you preclude ever going back in our lifetimes to actually land?
THAT is why I say if you’re going to go at all, go for the landing. There is simply no other point to it.
Now, there are others who want to plant a full-blown colony starting with that very first landing. This, too, is an EXTREMELY unrealistic expectation! Mars is a very harsh place to live: there is no air to breathe but what you bring or make, there is no water to drink but what you bring or make, and there is no way to grow any known food crops except inside pressurized buildings specifically constructed to provide Earth-like environments.
There are lots of ideas and some lab demonstrators for the means to make air to breathe, and water to drink, and even rocket propellants, and for how to construct pressure-tight buildings inside of which people could live and grow food. There’s more than one approach proposed for all of those things. Which is the best in each case is not my point here.
My point is: NOT ONE single piece of such equipment is known “for certain” to work as advertised at real Martian site conditions! Because none has ever been to Mars. If the gizmo doesn’t work right, and you have bet the crew’s lives on it, then they will die. Mission plans that bet lives on untested equipment on that very first trip are therefore unethical to the point of attempted murder! There is no logical way around that, either.
Why don’t we know this stuff will work “right” on site? Two reasons: (1) no two sites on Mars will ever have the same exact conditions, a situation that is same as here on Earth, and (2) the variation from site to site will be way too wide from “average”, just the same as it is here on Earth. You simply cannot design for conditions that you cannot anticipate, and Murphy’s Law says you WILL encounter the unanticipatable! (Because of this variation effect, I think you need to explore more than one site during that first trip. But others may disagree.)
What that uncertain success says is that the “right” expectation for your first landing is to try out all your technologies and gizmos for making air, water, propellant, and building construction on that first mission. But, you must ALSO bring all the supplies to accomplish said mission from Earth, in effect thereby assuming that none of your gizmos will actually work.
That is the ONLY ethical thing to do, and it really applies only to that first landing. After that, you will know very much more about how well your gizmos actually work.
The return for doing it this way is three-fold: (1) you get your crew back alive, regardless how the experiments turn out, (2) you identify what works and what doesn’t work with your gizmos, so that they WILL work “right” next time, and (3) they don’t have to be the full-size, full-weight items on that first field trial (leave that for next time). Doing this experimentation, plus exploring by rover and on foot, is what gets you past “flag-and-footprints” to something really useful.
What that means is your first crew on the surface of Mars lives inside of whatever hardware they brought from Earth. That could be disposable habitats, or it could be the vehicles they landed in. While there, they need to experiment with things like a concrete equivalent, local stone masonry construction, “ice-crete”, and similar, but they themselves need not succeed at building anything just to survive! What they accomplish and learn applies to subsequent missions, not this first one.
You might well ask “what subsequent mission?” since I already made the point above that it is very likely that there will be one, and only one, government-funded mission to Mars. My answer is that the second trip is going to have to be some sort of public-private joint venture.
We actually do have a couple of visionary outfits that might step up and do this (and their names are NOT Boeing or Lockheed-Martin). It’ll happen a lot quicker if that first landing identifies the right site, and how to go about making air, water, propellants, and buildings inside of which to live and grow food. If you don’t get that foundation done, it may be several decades before any private entity goes. It’s called “risk reduction” to make the up-front investment seem more sound.
It is that SECOND public-private partnership landing which establishes an experimental base to be expanded over time, a base that gradually shifts from Earth-sent supplies to “home-grown” supplies as the bigger gizmos go operational and start “pulling their weight”. Sometime shortly after that second mission is likely when the government quits funding this stuff entirely!
Once this experimental base is fully successful at supporting itself while occupied, with minimal stuff from Earth, then you can start thinking about permanent occupation. This is true whether with permanent or still-rotated crews, or a mix of both. It is at THAT point that you finally created your first settlement, after about the third or fourth mission. Eventually, that is what grows into a real colony on a century timescale, and by that time, we may have actually figured out an economy that works for this enterprise. (Today is far too soon to worry about interplanetary economies, in my opinion.)
Therefore, that FIRST landing need not set up any of the actual facilities for a permanent base, but it DOES need to answer all the essential questions for HOW to go about doing that! THAT is the right set of expectations for that first landing! Anything less is “flag-and-footprints” nonsense, anything more is “biting off way more than can be chewed”, or too expensive, or probably both.
A lot of participants on these forums are not going to like what I said here. But that doesn’t make it any less true.
GW
Last edited by GW Johnson (2017-04-17 15:10:55)
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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GW -
Couple of comments:
1. A lot has been tested and shown to work on Mars via the rovers.
2. I am surprised you don't reference Musk. Surely if anyone is talking about landing a colony in one go, it's Musk. Is he unrealistic? It seems not - he has a very good proven track record of delivery. I think there are organisational problems with his vision but in terms of the technology it seems there is no particular reason to doubt it will work.
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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GW-
I agree with much of what you stated in your post. I also agree that the way will not be led by Lockheed Martin or Boeing; they're too addicted to cost-plus schemes. On the other hand I believe Elon Musk has enough fire in his belly and the smarts to do what others only talk about.
You are correct about the first mission--it better survive to come back, and indeed accomplish some real research while there. The Flag and Footprints model doesn't excite me at all. Colonization will come, but it (first mission) needs to set an example of how to exist and survive while there--a "Proof of Concept" demonstration to put it in Corporate terms.
P.S. (added as an edit): Murphy was an optimist.
Last edited by Oldfart1939 (2017-04-17 15:49:12)
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If with reusable rockets Space X can get the cost of launch to LEO down to say $2500 per kg, your 63 x2 tonne launches cost only
$ 315 million. That's really an amazingly small figure in terms of the overall budget which I think will be dominated by development and monitoring costs. However, when you look at all the development work already done by Space X and NASA in various areas, even there I think we are going to see far less expenditure from the start line than we expected say 10 or more years ago.
OK, I found my original sheet of calculations, now rendered obsolete by SpaceX; the upgraded Falcon Heavy can now deliver 63,000 kg to LEO. This is composed of the following components: Upgraded Dragon 2 capsule with seats for 5 astronauts; 7000 kg. Extended and enlarged trunk stage, now integral with the capsule for crew accommodation; 14,000kg. This includes a crew in transit, water supply and 4760 kg of food. Also included is a water collection/reprocessing system and air purification devices. calculates to 2800 kg Oxygen which will be augmented through a small Moxie unit recycling exhaled CO2 from crew and dumping the CO by-product. Total crew weight is 440kg.In the storage area we can haul an additional 4000 kg of food and 2000 kg of personal clothing, protective gear and some science instruments. Calculated 6000 kg for structure and accommodations (sanitary facilities, some exercise equipment, bunks, comm equipment, etc.). This leaves 42,000 kg for the Mars landing engines, fuel, and landing legs. Rounding down to 38,000 for onboard UDMH and NTO, 4,000 can be distributed between spacecraft structure and additional equipment.
Mated to this vehicle at the ISS will be a TMI booster stage powered by UDMH and LOX. Available mass is net: 63,000 kg, of which 6,000 kg will be hardware. Depending on the flight trajectory and flight time (I calculated 200 days of food, plus a 40% margin for error), we need an absolute minimum delta V of 3.4 km/second. The 200 day transit requires closer to 3.6 km/second. This initial booster gets us a delta V of 1.15 km/second. The fuel onboard the spacecraft itself is sufficient-plus to get us to Mars with a reserve for propulsive landing. We can fudge-factor some of the payload down, if necessary for a safe(r) landing reserve. This is all a crude calculation based on the Rocket equation, and as a 2 stage departure. It could be given a larger margin of error through use of some SRBs during the first boost from LEO.
What this all accomplishes is getting a crew of 5 on Mars, with an onboard supply of food for an additional 250 days. Mission success depends on prepositioned ERV and additional food, with associated habitat and equipment.
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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Louis:
I didn't mention Musk overtly, but implied him, and perhaps Jeff Bezos, by their absence from the list of gluttonous hogs sucking at the public tit. I don't know if Musk's outfit can pull off building the giant vehicle design concept he revealed at the Guadalajara meeting. I'm pretty sure that if he does, there will never be very many of them, and each will fly only a few times. His presentation actually said that.
And, it emphasized that he is providing a transportation system while others (unidentified) are to use it to build a colony. Bezos I think is initially focused on the moon, but any one-way cargo transport to the moon can be a one-way cargo transport to Mars. It's the same delta-vee, if you plan to do direct entry at Mars from your interplanetary trajectory.
Oldfart1939:
Murphy was definitely an optimist. I spent 20 years doing new defense product engineering development and test, mostly rockets and ramjets. I ran into that unpleasant little truth about Murphy nearly every single day. I'm still here because I had to learn (on the job) how to be a professional coward working in an explosives plant.
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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GW-
After doing large scale organic syntheses for ~ 45 years and still alive to write about it? Yeah, I learned the hard way about Murphy. I never had a major explosion, but several fires. Every day was a new learning experience.
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I think the group has finished with commenting on the "2020: Demonstration flight of Red Dragon " and its time to move onto "2022: Follow-up Red Dragon mission"....
The Red dragon capsule will need to be upgraded to allow for more than what we are at for a much greater than 2mT payloads but with only a 2 year cycle is that going to be suffiecient time to ramp up payload capability. The greater need is due to the much larger masses of the preload items.
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SpaceNut-
Check my post #20 of this thread.
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Ya missed it in the big post
SpaceNut-
SpaceX should also consider scaling up the Dragon capsule to make it (1) taller, and (2) increase the base diameter to 5 meters. The extended trunk could accommodate up to seven, but a crew of 5 would seem more adequate utilization of space and supplies for the Hohmann transfer trajectory to Mars orbit. Once before I calculated this to be in the 22 metric Tonne empty mass category, and fully fueled could carry 30 metric Tonnes of hypergolic fuels. It could be flown unmanned to and docked with the ISS through the docking hatch atop the Dragon Heavy vehicle. This is--yes, a different shaped "tuna can." We couple this while docked with a fully hypergolic fueled booster massing 63 metric Tonnes. This fuel could, in principle, be used in part to assist the Earth departure and still have enough to execute mid course corrections, enter Mars orbit, and carry out the Mars landing. This could be flown experimentally in my 2024 mission, or as a cargo carrier as early as 2022.
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SpaceNut-
I'm banking heavily on the engineers at SpaceX, but waiting to see how well they do with the circumlunar trip scheduled sometime in 2018 before making any more cheerleading comments.
One of the real keys to progress towards these deep space missions is a major commitment to look at other fuels, particularly the hypergolic hydrazine-NTO combinations. A step in that direction could be taken through building a modified Falcon second stage using MMH in place of RP-1, but continuing to use LOX as the oxidizer. That would marginally increase performance by 6-7%, and gather some experience for building a more powerful Earth departure stage. I really don't know how well LOX will store onboard for longer space voyages without evaporative/boil off losses. For this reason alone, I favor the combination of NTO and one of the several hydrazine derivatives and combinations of them for the Mars landers and Earth Orbit departure vehicles, as well as for mid course corrections.
If you check my earlier posts this thread, you will see that I'm counting on prepositioning a LOT of food and survival supplies before the first manned mission.
W/R Elon Musks big mothering rocket--I suspect even he will realize that the jump he intends to make may be a rocket too far, and build something smaller as an intermediate step, which is what I've been harping on, in this thread. Many of Musk's other plans have been subject to modification through contact with reality.
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Monomethyl hydrazine (MMH) is actually pretty good soak temperature-wise: 1-atm boiling at 189.5 F and freezing at -62.3 F. It lists as 1.0 psia vapor pressure at 77 F and 9.0 psia at 160 F.
NTO is storable but pretty "touchy" about it: freezing and boiling are listed as 11.8 F and 70.1 F respectively. But, its vapor pressure is 17.2 psia at 77 F and 111 psia at 160 F! You have to keep it under pressure and within a narrow range of temperatures.
IRFNA is not so sensitive to storage conditions at 1 atm -63.4 F to 150 F, and vapor pressure 2.57 psia at 77 F and 19 psia at 160 F. But it performs poorer. However, it is hypergolic with any of the hydrazines and even kerosene. For those not familiar with it, this is 83% nitric acid, 15% NTO, and 2% water. The acronym stands for "inhibited red fuming nitric acid".
NTO-MMH Isp ~ 288 s sea level and 338 s vacuum (comparable +/- 1 sec with hydrazine, UDMH, and Aerozine-50)
IRFNA- UDMH Isp ~ 272 s sea level and 320 s vacuum -- a bit lower than NTO-MMH but a lot more storable in practical terms.
IRFNA-RP-1 Isp ~ 263 s sea level and 309 s vacuum
For comparison:
LOX-RP-1 Isp ~ 299 s sea level and 351 s vacuum
LOX-hydrazine Isp ~313 s sea level and 367 s vacuum -- note that this beats both LOX-RP-1 and LOX-methane!
LOX-methane Isp ~ 310 s sea level and 365 s vacuum
Those listings are from my ancient Pratt & Whitney handbook. Sea level is 1000 psia to 14.7 psia at 100% kinetic energy efficiency, and vacuum is 100 psia through 40:1 area ratio at 100% kinetic energy efficiency.
GW
Last edited by GW Johnson (2017-04-19 12:51:59)
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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GW-
I specifically chose the combination of hydrazine with some MMH added for freezing point depression and reduced sensitivity towards shock; especially when paired with LOX, it makes a very good potential performance upgrade for Falcon 9 second stage. It then beats LCH4 in Id by a substantial margin.
My argument is SpaceX/Elon Musk needs to build something of an intermediate rocket for "proof of concept," before shelling out $10 Billion to build his "big mothering rockets." As a scientist, I look with a jaundiced eye at one step quantum leaps in size and complexity. I've never, for example, taken a bench scale chemical reaction straight to a 1000 gallon reactor without running it in the pilot plant and--say a 20 gallon to 50 gallon scale--first. And if someone else wanted to do it--I'd make sure I was taking a personal day off!
Last edited by Oldfart1939 (2017-04-19 14:05:58)
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I got involved in a project once where somebody wanted to do exactly that. Bench scale straight to industrial size. they wanted the product on the market double quick so would carry out the full scale design whilst they built and ran the pilot project. They were really confident, so we started designing a plant and procuring hardware for installation in a new building at an existing site, as requested, whilst they built a scale up.
Result was exactly as you would expect, Oldfart. Pilot scale didn't work properly and product was not nominal in either quantity or quality.
Eventually the whole thing was abandoned at considerable cost.
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