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This thread of for comparing detailed mission plans focusing on Propulsion methods. GW has produced a modular NTR based mission with spin based artificial gravity
http://exrocketman.blogspot.com/2012/07 … icial.html
And I'm going to do a SEP counter proposal in equal detail, but first I'm going to try to get the ground rules established to allow as complete and apples-2-apples comparison. I've looked over GW's mission and extracted what I think are the criteria that need to be replicated.
* Launch constraints on volume and mass of Falcon Heavy (50 mt), with option to use the other EELV's.
* Trajectory from LEO to LMO and back again bringing the transit habitat back to LEO but leaving the lander mass in LMO for it's mission to be conducted from.
* Offload 120 mt of lander/surface payload modules at LMO massing 30 mt each. (Personally I don't think that's adequate but that's another topic)
* Provide 50 mt of Habitat module/s during transit (reusable) and 50 mt of Consumable filled module/s each for out and inbound transit. (The total here seems to be enough for the entire 27 months so I assume the landers are stocked separately and are of such negligible duration as to not effect to overall consumable budget)
* Total mission duration of 27 months. (GW's mission keeps the crew in LMO with only brief surface forays so the 8.5 month transit time is not a constraint I feel needs to be replicated when the crew is in a radiation environment nearly identical to interplanetary space for almost the entire mission)
GW's mission also provide 1g artificial gravity to crew during transit I'm a bit doubtful on this as first we don't know what the minimum therapeutic g is, second their is no mass allocated towards achieving this structurally in GW's proposal, just a calculation of the RPM necessary to create the g given the long length of the vessel. I don't think it's necessary to replicate this. My personal preference is for a centrifuge inside of an inflatable, possibly just a 'moving sidewalk' track for running/jogging if that were sufficiently therapeutic. Their is such a huge unknown here I don't think it's worth speculating on and I'm going to confine my proposal to the above constraints and not deal with gravity, penalize it what ever mass you think is appropriate.
GW are their any other constraints/goals that you think I've missed or that you disagree with?
Last edited by Impaler (2012-07-22 05:18:32)
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This thread of for comparing detailed mission plans focusing on Propulsion methods. GW has produced a modular NTR based mission with spin based artificial gravity
http://exrocketman.blogspot.com/2012/07 … icial.html
And I'm going to do a SEP counter proposal in equal detail, but first I'm going to try to get the ground rules established to allow as complete and apples-2-apples comparison. I've looked over GW's mission and extracted what I think are the criteria that need to be replicated.
* Launch constraints on volume and mass of Falcon Heavy (~50 mt), with option to use other EELV's.
* Trajectory from LEO to LMO and back again bringing the transit habitat back to LEO but leaving the lander mass in LMO for it's mission to be conducted from.
* Offload 120 mt of lander/surface payload modules at LMO massing 30 mt each.
* Provide 50 mt of Habitat module/s during transit (reusable) and 50 mt of Consumable filled module/s each for out and inbound transit.
* Transit times and total mission duration of 2-3 years with interplanetary transit times of 6-8 months
I'm interested in producing a table to compare mission architectures?
What columns should the table have? Here are my suggestions:
SSTO/or no. of stages
Fuel/propellant/engine description
Pre-landing robot and other preparatory missions, excluding
training and test missions i.e. only missions directly designed to facilitate the
landing and survival of the crew(s) on Mars (give number of such missions if applicable)
Number of separate transit vehicles going to Mars
as part of the mission (most will be one but I favour two)
No. of crew in each vehicle
Total number of launches
Orbital assembly (yes/no)
Mars transit vehicle description... etc. (indicate if artificial gravity is used)
Transit hab description
Journey to Mars (Hohmann etc)
EDL for Mars
Immediate procedures following landing
Energy source on Mars
Habs on Mars
Use of rovers?
Main activities on Mars
EVA details
Duration of Mission
Ascent and return procedure
Total duration of mission
Comments and timeline box
Any other suggestions?
Let's Go to Mars...Google on: Fast Track to Mars blogspot.com
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This thread of for comparing detailed mission plans focusing on Propulsion methods. GW has produced a modular NTR based mission with spin based artificial gravity
http://exrocketman.blogspot.com/2012/07 … icial.html
And I'm going to do a SEP counter proposal in equal detail, but first I'm going to try to get the ground rules established to allow as complete and apples-2-apples comparison. I've looked over GW's mission and extracted what I think are the criteria that need to be replicated.
* Launch constraints on volume and mass of Falcon Heavy (~50 mt), with option to use other EELV's.
* Trajectory from LEO to LMO and back again bringing the transit habitat back to LEO but leaving the lander mass in LMO for it's mission to be conducted from.
* Offload 120 mt of lander/surface payload modules at LMO massing 30 mt each.
* Provide 50 mt of Habitat module/s during transit (reusable) and 50 mt of Consumable filled module/s each for out and inbound transit.
* Transit times and total mission duration of 2-3 years with interplanetary transit times of 6-8 months
Good notion, we can move the discussion to where it's slightly less OT. When I finally stop partying like I am doing lately (holidays! ^^), I might take a stab at it and try to implement the various tricks to see the effects on each (by "tricks" I mean aerobrake, basing at high mars orbit instead of low, departing form a Lagrange point/HEO...).
Rune. I do have like 5 different threads open in tabs that I would like to write a reply to...
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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[(by "tricks" I mean aerobrake, basing at high mars orbit instead of low, departing form a Lagrange point/HEO...).
Just wanted to give my take on aerobraking/aerocapture, what I think is important to remember, and how it relates to manned SEP missions.
So first, aerobraking: its been used on half a dozen (non re-entry) missions, slowing down the craft over the course of a few hundred passes. So far its been done via craft with solar panels, using the large panels as drag brakes. The craft is moved into an elliptical orbit, and using the atmospheric drag at the lowest altitude portion of its orbit, it lowers the altitude of the "high end" of its orbit.
The problem with aerobraking (as I see it) is that it takes a long time: velocities between 1-2km can take upwards of 50-100 days; this couldn't be shortened for a manned mission, because - keeping safety in mind - you have to assume the worst possible atmospheric density (there is currently no way to accurately predict the exact atmospheric density on mars at a certain date and time - at altitudes where the aerobraking would take place [100+ km], atmospheric density varies (2-3x on each pass). Spending this long in transit would expose you to un-needed radiation; and on the return trip to earth, while aerobraking here, you would be aerobraking (100+ passes) through the van-allen belts.
This brings me to my next point regarding the ability to aerocapture - Solar panels can't survive too large of a dynamic pressure (which is the pressure on the craft by the atmosphere) or heat flux (the heat (that is convected/radiated into the aerobraking/aerocapture craft) from the shockwave caused by hitting the gas particles at hypersonic velocities) too large (obviously) before seriously degrading the performance, or damaging the panels; putting aerocapture (only one pass through - as that is considered true aerocapture) with solar panels out of the question. The Mars Odyssey had an estimated heat flux (during some of the worst passes of the aerobraking) of 500 W/m^2; any higher, and it would have damaged the efficiency of the panels. However take this aerocapture point with a grain of salt, as solar panels have improved since 2001 (launch date of Odyssey - and how outdated the information I found on the subject is); not sure how durable (i'm sure its increased significantly) current solar panel tech is (hopefully someone can provide info on the state of current solar panels).
My first thought was that one could fold in the solar panels (no clue how it could be done) during aerobraking, saving the panels. However, the problem with this is that it increases the ballistic coefficient; meaning you have to go further down into the atmosphere, which in turn would create a higher heat flux, damaging the solar panels (at least those used on the Odyssey); facilitating the need for an apropriate heat shield.
Then there's the matter of whether or not spending the time aerobraking is even feasable for a manned mission (50+ days), as turn time on a mission can save alot of money - the more missions you can fly in the same time increases any given mass throughput. It's my opinion that aerocapture would be the best option (as Zubrin's Case for Mars suggests (note that's using chemical propulsion, so I guess it's not really relevant) - one pass through; which as of 2001, was impossible for solar panels. The only other option would be to flip the craft around and point the "exhaust" in the opposite direction - however being the low thrust system it is, you have to wonder how much time it would add / how viable even that is.
On a second note:
GW's mission also provide 1g artificial gravity to crew during transit I'm a bit doubtful on this as first we don't know what the minimum therapeutic g is.
The point GW made was that we don't know what the minimum therapeutic g is (like you said), so to be safe and have 100% certainty that we could without a doubt "hold up" during the long flight, just have the craft provide a full 1g of gravity.
My personal preference is for a centrifuge inside of an inflatable
Something like an inflatable ring sounds promising - see Natilus-x [ http://en.wikipedia.org/wiki/Nautilus-X ]
The more recent research on RPM's humans can withstand that I posted over in the "landing on Mars" thread would directly relate to an inflatable ring. Reposted below.
http://www.ncbi.nlm.nih.gov/pubmed/1102 … t=Abstract
Small excerpt from the abstract:
"Early studies suggested that 3 rpm might be the upper limit because movement control and orientation were disrupted at higher velocities and motion sickness and chronic fatigue were persistent problems. Recent studies, however, are showing that, if the terminal velocity is achieved over a series of gradual steps and many body movements are made at each dwell velocity, then full adaptation of head, arm, and leg movements is possible. Rotation rates as high as 7.5-10 rpm are likely feasible. "
And Finally:
I apologize for being so objective Impaler - Common sence can tell you that a very well designed fully reusable manned SEP vehicle could be the cheapest way to go; it's also an option that will never go away regardless how the political winds shift, because it is the (arguably)safest - without requiring any mega-infrastructure (microwave/laser sail ect). My only question is how feasible it is.
Last edited by NeoSM (2012-07-22 21:03:42)
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My two-way delta-vee of 8 km/sec is probably a little high, except for realistic plane changes. Ballpark realistic under real 3-D conditions, I think.
I used heavier-than-min-calculated consumables mass to cover using frozen food. That freeze-dried non-refrigerated stuff they use now doesn't last more than about 1-1.5 years. Frozen does, it'll go decades if need be. My numbers are just ballpark guesses.
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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