Author Topic: MCT Speculation and Discussion Thread 2  (Read 281871 times)

Offline Eerie

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Re: MCT Speculation and Discussion Thread 2
« Reply #180 on: 11/14/2014 07:16 pm »
assuming that all that's been said, that Elon want's to send 80,000 people to Mars per year, the logistics of it is staggering.

Stying with the MCT craft hauling 100 people each, that's going to take 800 craft, per year to Mars, or 2000 MCT's per 2.5 year cycle!

The MCT's wouldn't be sufficent to sustain this kind of work load, and accidents would happen.  I think I have a handle on how this could be done, but it would take at least 5 to 10 years of ramp up time to make possible.

Erm, optimal launch window is much smaller. You'll have to launch everything in a couple of months.

Offline Robotbeat

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Re: MCT Speculation and Discussion Thread 2
« Reply #181 on: 11/14/2014 07:36 pm »
Musk isn't looking for those types for his colony. He's openly skeptical, scoffing at Mars One's plans. No doubt many of those 80k would be people who don't intend to stay their entire lives on Mars. But once you have a thousand, ten thousand, hundred thousand people there, it's more like deciding to live in Minneapolis in January (you really can't go outside for more than a minute except after spending 15 minutes bundling up, but all the buildings are interconnected in the downtown with tunnels and skyways and people have climate-controlled garages so that's not a show stopper) than it is anything at all like a one-way suicide mission. You'll need a few thousand incredibly driven and bright people at first no doubt, but you don't need and don't want anti-social "suicide geeks."

No, Mars is more like winterover on the South Pole, only for 3 years instead of 9 months, and the conditions outside are much worse.

You know what, let's say someone built us a perfect underground base on Mars, with greenhouses, gyms and swimming pools. Still, what's the attraction? Why would you want to spend your life there?
Sounds sweet. An entire virgin planet. With lots of other smart and driven people doing something that has lasting, historical, existential significance. That's all anyone can ask for.
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Offline Robotbeat

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Re: MCT Speculation and Discussion Thread 2
« Reply #182 on: 11/14/2014 07:42 pm »
I mean sheesh, am I the only one that is motivated by something other than just living a life of comfort??

Significance is a powerful motivator.
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Offline Eerie

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Re: MCT Speculation and Discussion Thread 2
« Reply #183 on: 11/14/2014 08:03 pm »
Sounds sweet. An entire virgin planet. With lots of other smart and driven people doing something that has lasting, historical, existential significance. That's all anyone can ask for.

What's the significance of spending your life in a box, unless you are an anchorite? There are many people who do research on the South Pole, but I don't recall any of them wishing to actually live there indefinitely. The same will be true about Mars. A research base - sure. A colony - bloody unlikely.

And I don't think you need 80k people per year for a research base. 80k people in total on Mars will probably be more than enough to research the crap out of it. :-)
« Last Edit: 11/14/2014 08:05 pm by Eerie »

Offline RanulfC

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Re: MCT Speculation and Discussion Thread 2
« Reply #184 on: 11/14/2014 08:03 pm »
Below is my speculative MCT design.

I constrained the design by following as many Elon and SpaceX statements as possible.  I tried to optimize for both development and operational costs.  I got most of my inspiration from the other excellent designs in this thread, but tried to make something unique.

Nice design but... Lord-n-Lady how do you get to the surface from that thing? Jump? :)
Rope ladder or cable lift. Do you even treehouse? ;)

Yup, but not in a space suit and I DO recall the times the rope came loose and the "boards" from the ladder pulled out... ("Hey I needed the other nails" {he left one} "to hang the sign over the door!" Note the one that said "door" btw :) )

And getting your luggage down is going to be a chore :)

Randy
From The Amazing Catstronaut on the Black Arrow LV:
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Offline Robotbeat

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Re: MCT Speculation and Discussion Thread 2
« Reply #185 on: 11/14/2014 08:21 pm »
Sounds sweet. An entire virgin planet. With lots of other smart and driven people doing something that has lasting, historical, existential significance. That's all anyone can ask for.

What's the significance of spending your life in a box, unless you are an anchorite? There are many people who do research on the South Pole, but I don't recall any of them wishing to actually live there indefinitely. The same will be true about Mars. A research base - sure. A colony - bloody unlikely.

And I don't think you need 80k people per year for a research base. 80k people in total on Mars will probably be more than enough to research the crap out of it. :-)
There are small, permanent Argentinian and Chilean colonies in Antarctica (and mass colonization by the West is not allowed due to treaty... Though to accurately describe that will take a while). Children have been born and raised there. And a totally new planet is yet more compelling. Not everyone has to fit your narrow idea of what kind of life is worth living.

I also take it you're not from a very northerly country like Russia, Scandanavia, North Dakota, or Minnesota.
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Offline RanulfC

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Re: MCT Speculation and Discussion Thread 2
« Reply #186 on: 11/14/2014 08:26 pm »
I mean sheesh, am I the only one that is motivated by something other than just living a life of comfort??

Significance is a powerful motivator.

Uhm, no you're not obviously however might I point out that "significance" is in fact not THAT powerful of a motivator. In fact its actually one of the LEAST powerful motivators, historically. People just do NOT react to it as  the basis for motivation to do something highly unusual like colonization.

Money, power, opportunity, THOSE are powerful motivators. A page in the history books? Hardly. It motivates (in todays population of billions) hardly hundreds let alone thousands. Musk is pretty well aware of this though he lets his own vison overcome him quite often and that in itself is a motivator. But no, if I see you volunteering to go to Antarctica for the rest of your life you MIGHT be able to convice me that you really want to go to Mars but not before you can explain and articulate to me HOW your going to live there in detail. With diagrams and cost analysis please :)

People also have this false idea that exploration is colonization and its not the two are very different and the former is normally actually easier than the latter.

The bare faced truth is the majority of humanity happens to accept if not like their current lot in life and they would be hard pressed to find the motivation to move several hundered miles let alone millions and endure hardships they did not have to. And motivation to do so in and of itself has to be VERY powerful indeed even for that. There ARE actually quite a number of people who would (and do) jump at the chance to move to space be it space, the Moon, Mars, whatever but they are only a tiny fraction of a percentage of the human race.

YOU want to go I understand that but you yourself have to understand how rare you are and NOT just because you are "motivated by something other than just living a life of comfort" because even you don't really understand or comprehend JUST how "uncomfortable" colonizing Mars would be. (Hint: WE don't know because we've not had enough experiance ON Mars to make more than generalizations. Those generalizations are not enough to base a colony plan on)

Hell "I" want to go and live in the clouds of Venus about the same way that Musk want's to live on Mars, but I fully understand that the chances are vanishingly small (non-zero would probably be about the most accurate way to put it) because nothing of the infrastructure is available to do so. Not that it's stopping me from at least working on the possibilities mind you.

I'm sure Musk understands this is the same with Mars and he'd like to change that if he can but it's a process and it's going to take time, effort AND the discovery of some form of motivation that DOES resonate with more of humanity to accomplish. "Significance" is one of his motivators obviously but it will take much more than that (and lower prices) to convince people to imigrate to Mars (or anywhere else) in significant numbers. A LOT more.

Randy
From The Amazing Catstronaut on the Black Arrow LV:
British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

Offline Robotbeat

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Re: MCT Speculation and Discussion Thread 2
« Reply #187 on: 11/14/2014 08:36 pm »
You vastly underestimate how many people would want to move to a city on Mars. I'm talking city, because that's what a 1 million person colony is. A very large city, in fact, by American standards. Not a box, but a city. A large, diverse, and expansive city on another planet.

You only need 10 people who'd want to live in a tin can, 100 who'd live on a base, 1000 in a settlement, 10,000 in an interconnected town the size of a large indoor shopping mall, and 100,000 who'd live in a small but growing city. 1 million who'd live in an enormous, largely self-sufficient city.

To be honest, I have a harder time understanding why people are content to live in the suburbs all their lives.


200,000 people considered Mars One's crazy one-way scheme to cramped quarters. I wasn't one of them. I sincerely doubt there's anything less than hundreds of thousands of people in the world who'd want to join such a project. The world has over 7 billion people, and by the time any of this is relevant will be almost 10 billion.
« Last Edit: 11/14/2014 08:45 pm by Robotbeat »
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Offline lele

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Re: MCT Speculation and Discussion Thread 2
« Reply #188 on: 11/14/2014 08:43 pm »
I made a thread about would-be colonist motivations since it's quite off-topic here :)

Offline RanulfC

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Re: MCT Speculation and Discussion Thread 2
« Reply #189 on: 11/14/2014 08:47 pm »
I made a thread about would-be colonist motivations since it's quite off-topic here :)

Thanks :)

Randy
From The Amazing Catstronaut on the Black Arrow LV:
British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

Offline CyclerPilot

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Re: MCT Speculation and Discussion Thread 2
« Reply #190 on: 11/14/2014 10:33 pm »
How fast do you hit the ground after jumping from 30 meters on 0.3g?

Really, very nice design.
It resembles a possible dragon2 + stage2 glued together which I think is a very interesting option for near term stage reuse.

Thanks.

30m at 0.3g?  Plenty enough to die.

To go into more detail on exiting the MCT...  A pressurized xfer module has to 'dock' to the MCT, be loaded up, and then be moved to the ground and onto a rover that can dock with the colony.

Early on, MCTs would have to provide the pressurized xfer module, a hoist, and even a rover.  When the colony is more established, MCT's wouldn't need to bring these things.

I'm picturing a scissor lift rover that would need to be originally delivered via and unpressurized MCT and placed on the ground by a crane delivered in the same MCT.

Offline Cinder

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Re: MCT Speculation and Discussion Thread 2
« Reply #191 on: 11/15/2014 01:56 am »
Sounds sweet. An entire virgin planet. With lots of other smart and driven people doing something that has lasting, historical, existential significance. That's all anyone can ask for.

What's the significance of spending your life in a box, unless you are an anchorite? There are many people who do research on the South Pole, but I don't recall any of them wishing to actually live there indefinitely. The same will be true about Mars. A research base - sure. A colony - bloody unlikely.
Either way, and closer to topic, this potential flaw in the MCT plan ought to be much clearer by the time SpaceX starts preparations in earnest.  The Apollo program's influence on people to go on to study STEM is inarguable, yes?  A program like SpaceX's MCT, along with the state of everything else currently on schedule to be visible to the public by the time MCT ramps up - could you argue that they won't have a similar effect? 

People don't have to perfectly acclimatize to initial colony life on Mars for the colony to succeed and for MCT to have a colony to service.  Would SpaceX really move forward if they had evidence that sufficient demand for their supply wasn't there?
« Last Edit: 11/15/2014 01:58 am by Cinder »
NEC ULTIMA SI PRIOR

Offline Hotblack Desiato

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Re: MCT Speculation and Discussion Thread 2
« Reply #192 on: 11/16/2014 10:45 am »
regarding MCT speculations, how about this:

first: there are several generations of MCTs


as a precursor, they could use the red dragon project. I guess it would be nice to see if that is actually possible to land on mars, maybe even as sample return mission. the red dragon is not necessary, but they could gather experience at flying interplanetary.

with the first flights of BFR, they could send a prototype MCT to mars. this prototype is unlike the statements of elon musk a 2 stage system.

MCT MK1 (+prototype)

stage 1 are engines, ISRU-unit (methane production), large surface solar panel and a few other important systems. stage 1 is necessary for landing on mars and then (without the surface solar panels*) it launches as a 2-stage rocket to a certain height seperates from stage 2 and lands again propelled. the prototype will contain the necessary hydrogen for the methane production. the regular MK1s will have a detachable methane production.

stage 2 is the unit which reaches mars orbit and returns to earth. it contains smaller engines, smaller tanks, solar panels and the proper heat shield to reenter earths atmosphere. three versions, crew, cargo and combined. first, there will be combined and cargo-MCTs flying.

stage 1 returns to the landing site and awaits a little maintenance, in order to work as chemical plant for further fuel production.

MCT MK2

it's a single stage to earth system which saves weight and reduces complexity. it no longer contains surface solar panels and the methane production unit, thus reducing the mass and allowing more cargo to be transported to and from mars.
the MK2 will start on top of the BFR, flies to mars, lands on mars, gets hooked up with the MK1 stage 1 (by local population), and gets refueled. after a short inspection, it launches back to earth. on the way back, if empty or containing samples, it could use a vasimr-engine to reduce fuel requirements. this vasimr could be aswell important for reducing the required time at the flight to mars. 4km/s methalox + 1-2km/s vasimr could enable faster trajectories. and for the flight to mars, they require power to keep the passengers alive and happy, energy that is available for the engine on the flight back.
if it contains people who want to travel back from mars to earth, it has to fly a shorter trajectory.

MCT MK2+ and 3

the only difference between those 2, MK2+ are refurbished and upgraded towards MK3, whereas MK3s are built freshly as MK3. with additional experience about handling the MCTs and improvements in the design, they can fly to mars, land on mars, launch to mars orbit, land on mars and launch back to earth. this would allow to launch an orbital module by BFR (currently, I'm thinking of an upscaled bigelow-module which can utilize the unique capabilities of the BFR). this orbital module acts like the orbital module of soyuz, just for more than 100 people. maybe MCT carries 100 people and the orbital module carries another 100 people, or it carries 200 people and there are 2 MCTs with 100 people each docked to it. or it's a combined crew-cargo flight, again with 1-2 MCTs docked.
for cargo, instead of a bigelow-module, it could just contain the cargo-modules, unpressurized (if the cargo can withstand it), and they get loaded into the MCT in orbit around mars.

these modules always stay in space, they will never land again.

the MK3 trades mission complexity with lower weight. but at this point of development, it should be possible.

post-MCT mars shuttle

at some point, the mars colony develops capabilities of maintaining and eventually even production of  MCTs and other spacecrafts locally. they don't need to be carried back to earth for maintenance anymore. at this point, the orbital modules travel between earth and mars on their own, and BFR (or something else) is just used to bring cargo and people into LEO. I guess, there'll be at least one large space station consisting of those bigelow-modules, that where used to derive the MCT orbital module.

I know, this isn't fully consistent with the things Mr Musk said, but it's they way I think that it could work.


*surface solar panels: in my opinion, those are quite large rolls of solar panels, a rover with the roll detaches from the MCT, connected just by a cable (for power supply). the rover rolls the solar panel onto the martian surface. 1,5m wide by 500-1500m length (depending on what is possible with an up to 1m thick roll). the mass of rover + solar panel should not exceed 3 mt. after laying the panel, the rover is still used for cleaning the panel from martian dust.


regarding the canada-topic. keep in mind, that Toronto is at the lattitude of Marseille, Vancouver at the lattitude of Nürnberg, Edmonton matches Berlin, Anchorage and Helsinki, and by then, I did not even start with Bergen, Trondheim and Tromso. not to mention Murmansk and Reykjavík
« Last Edit: 11/16/2014 11:01 am by Hotblack Desiato »

Offline Ben the Space Brit

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Re: MCT Speculation and Discussion Thread 2
« Reply #193 on: 11/19/2014 04:21 pm »
I'm wondering if MCT (the mission vehicle) will be basically based around the fundamental ideas of Mars Direct's colonial phase - multiple "tuna cans" to one location with CRV-derived orbit-to-surface shuttles. They'll carry down cargo and personnel and carry up personnel and propellent to refill the propulsion stage for the flight back to Earth. Others will be permanently Mars based, primarily to increase propellent upmass per cycle.

The BFR will fly up cargo modules and propellent tanks to top up what I assume would be LEO depots to service the other end of the 'railroad'. FH could be used to launch Dragon v.3 passenger vehicles to carry the new crew up to the crew transport vehicle.

The only significant change would be that the EDS would be retained rather than jettisoned before the Mars aerocapture, refuelled with Mars ISRU propellent and used for the Earth return phase. That would give the ERV far more hab space, especially if the prop tanks are 'bladder' types that shrink when emptied into the propulsion stage.
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Online guckyfan

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Re: MCT Speculation and Discussion Thread 2
« Reply #194 on: 11/20/2014 06:22 am »
On the Mars side, I'd expect a dedicated BFR upper stage doing work as a reusable Mars SSTO. That makes the return leg a lot easier, since the MCT does not have to perform both the ascent to Mars orbit and the full transfer burn by itself, which would require a lot of delta-v for a fast return.

But that would require capability of doing maintenance for MCT on Mars incl. the heatshield. I don't believe that capability will be available any time soon.

Now if there was fuel production in Mars orbit (say they find water and CO2 on Phobos) then the idea suddenly becomes much more feasible. They would not need refueling flights from the Mars surface in that scenario. And a lot less fuel ISRU on the surface as they no longer need to lift all the fuel for the return flight out of the Mars gravity well.

A BFR upper stage only really needs a heat shield if it is required to be capable of bringing payloads down with it. Otherwise, it does not need to be built for reentry. Just do propulsive braking like with the Mars transfer, there's no need to use the atmosphere for that. The payload mass to dry mass ratio would be so large that the penalty for propulsive braking ends up being small, much like for Earth first stage RTLS which has roughly similar delta-v requirements for boostback.

It is heavy enough by itself. Braking from orbital speed down to a speed where reentry is possible without heatshield would require a prohibtively high delta-v of at least 6-7km/s. No way of doing that propulsively with appreciable payload.

The amount of maintenance needed would depend on how reliable and serviceable the Raptor turns out to be, and on how bad the cyclic stresses on the cryogenic tanks are. If they are planning to eventually refly first stages within days on Earth, launching a Mars SSTO a few times a year would probably not be a huge deal.

Not a big deal on earth with its industrial base. It will take a long time before it is feasible on Mars. Especially the heat shield.

There is no need for multiple refueling trips either. Just launch the damn thing whole. There's just no need for it to lug something the size of a Falcon 9 first stage all the way back to Earth. This thing called "staging" improves payload a lot.

Not sure what you are talking about. We were talking of refuelling runs from Mars surface to Mars orbit. Sure it can be done. A SSTO and back to the surface without refuelling and delivering fuel as payload to the earth return vehicle is possible, sure. But it will require a lot of extra fuel over directly sending MCT back from the Mars surface to earth. The tanker weight needs to be lifted and Mars return performed.

Not at all clear to me what you mean with no need to lug something large back to earth. MCT goes back for reuse.

Phobos or Deimos ISRU (or more general asteroid ISRU around Martian space) would be a nice thing to have, and is very viable for a Mars roadmap that involves asteroids or visiting the moons of Mars before Mars itself.

That but as valuable for Mars landing missions for the Earth return flight.

Offline Nilof

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Re: MCT Speculation and Discussion Thread 2
« Reply #195 on: 11/20/2014 07:29 am »

It is heavy enough by itself. Braking from orbital speed down to a speed where reentry is possible without heatshield would require a prohibtively high delta-v of at least 6-7km/s. No way of doing that propulsively with appreciable payload.

Actually, that is quite possible, with significant margins, as long as you don't bring the payload down with you.

At 3600Ns Isp, the mass ratio for launching to orbit is exp(3.8/3.6) = ~2.9. For landing, you have another factor of 2.9, which gives a minimum required mass ratio of ~8.4 for the stage. For comparison, the Falcon 9 first stage has a mass ratio of 22.

To keep our numbers round, assume our Mars SSTO has a dry mass of 10 tonnes and can carry 200 tons of fuel, and let's round up 2.9 to 3. The US needs to save 20 tons of fuel for landing. But at a mass ratio of 3, 200 tons of fuel is enough to put 100 tons into orbit. So you're left with a  100 - 30 = ~70 ton payload to low Mars orbit, vs a 90 ton payload to orbit if it were fully expendable. The payload hit for fully propulsive landing is so small that a heat shield probably isn't the best option.
« Last Edit: 11/20/2014 07:41 am by Nilof »
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Online guckyfan

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Re: MCT Speculation and Discussion Thread 2
« Reply #196 on: 11/20/2014 08:23 am »

It is heavy enough by itself. Braking from orbital speed down to a speed where reentry is possible without heatshield would require a prohibtively high delta-v of at least 6-7km/s. No way of doing that propulsively with appreciable payload.

Actually, that is quite possible, with significant margins, as long as you don't bring the payload down with you.

At 3600Ns Isp, the mass ratio for launching to orbit is exp(3.8/3.6) = ~2.9. For landing, you have another factor of 2.9, which gives a minimum required mass ratio of ~8.4 for the stage. For comparison, the Falcon 9 first stage has a mass ratio of 22.

To keep our numbers round, assume our Mars SSTO has a dry mass of 10 tonnes and can carry 200 tons of fuel, and let's round up 2.9 to 3. The US needs to save 20 tons of fuel for landing. But at a mass ratio of 3, 200 tons of fuel is enough to put 100 tons into orbit. So you're left with a  100 - 30 = ~70 ton payload to low Mars orbit, vs a 90 ton payload to orbit if it were fully expendable. The payload hit for fully propulsive landing is so small that a heat shield probably isn't the best option.

You are doing heavy hauling in shifting goal posts.

First you talked about a BFR upper stage that implies LEO to earth return. Now you are talking Mars landing which is easier.

Second you suggested using MCT for lifting fuel. Which is heavy and costs a lot of extra fuel to lift and land but allows to do maintenance on earth. Now you pluck a dedicated Mars vehicle out of the thin martian air that can do only Mars launch and landing which implies full maintenance on Mars.

Offline Nilof

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Re: MCT Speculation and Discussion Thread 2
« Reply #197 on: 11/20/2014 08:55 am »
I am not suggesting the MCT to lift fuel. I am talking about repurposing a BFR upper stage as a Martian SSTO separate from the MCT. And that the MCT could be lifted by it so it doesn't have to do the full trip back to Earth with a single stage.

As I said in my original post, I envision the MCT as a vehicle with 2-3 km/s delta-v and optimized for areocapture/areobraking and landing with heavy payloads, while using a BFR upper stage for any delta-v intensive burns such as transfers and Mars liftoff.
« Last Edit: 11/20/2014 09:05 am by Nilof »
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Online guckyfan

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Re: MCT Speculation and Discussion Thread 2
« Reply #198 on: 11/20/2014 09:36 am »
I am not suggesting the MCT to lift fuel. I am talking about repurposing a BFR upper stage as a Martian SSTO separate from the MCT. And that the MCT could be lifted by it so it doesn't have to do the full trip back to Earth with a single stage.

As I said in my original post, I envision the MCT as a vehicle with 2-3 km/s delta-v and optimized for areocapture/areobraking and landing with heavy payloads, while using a BFR upper stage for any delta-v intensive burns such as transfers and Mars liftoff.

And I gave the reasons why I see a problem with that approach.

Offline Nilof

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Re: MCT Speculation and Discussion Thread 2
« Reply #199 on: 11/20/2014 09:55 am »
I am not suggesting the MCT to lift fuel. I am talking about repurposing a BFR upper stage as a Martian SSTO separate from the MCT. And that the MCT could be lifted by it so it doesn't have to do the full trip back to Earth with a single stage.

As I said in my original post, I envision the MCT as a vehicle with 2-3 km/s delta-v and optimized for areocapture/areobraking and landing with heavy payloads, while using a BFR upper stage for any delta-v intensive burns such as transfers and Mars liftoff.

And I gave the reasons why I see a problem with that approach.

...And some of these reasons(such as the issue of payload) were faulty and not grounded in actual calculations with the rocket equation. Separating the MCT from the transfer stages/mars ascent vehicle gives a noticeable increase in payload compared to the magical LEO->Mars or Mars-> Earth single stage MCT that most people seem to consider on this thread. It is also much simpler if you want to return the MCT within one synodic period. And it allows the rocket stages to be used between launch windows for other things.

Staging is just too good of an idea to give up on if you want to have a decent payload.
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

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