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Mars Colonial Transporter: What will it look like?

NSEP

By NSEP
in Science & Spaceflight

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CptRichardson

CptRichardson

Posted
Posted
3 hours ago, Nibb31 said:

How so? Most of his achievements were strongly subsidized by the US government and had a clearly defined customer base and business plan. Mars is nothing like that.

As I mentioned above, there is a lot of tech that needs to be developed and much of the tech that they do have doesn't apply. For example, most of their precision landing experience doesn't apply to Mars because those systems are based on GPS. They can't build their own GPS network on Mars (GPS sats are freaking expensive) so they will need to develop a whole new system based on optical recognition, prelanded nav beacons, or some other tech that doesn't exist yet.

As RedKraken said, their iterative development method won't work too well with launch windows every 24 months. They won't be able to afford rapid prototyping and crashing stuff to see if it works the way they usually do. Certifying a man-rated life support system and life-dependent reliable ISRU and refueling techniques is going to need many development flights before they can risk human lives on those technologies, and debugging is hard in these conditions.

 

You know, having a rocket with the power of the MCT would be just as useful in translunar space as interplanetary space, and the moon does make an interesting test target with which to test many of the technologies prior to going to mars...

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Rakaydos

Rakaydos

Posted
Posted
15 hours ago, Nibb31 said:

How so? Most of his achievements were strongly subsidized by the US government and had a clearly defined customer base and business plan. Mars is nothing like that.

The Raptor wasnt subsidized as an upperstage engine until recently, and it's already being sent to a test stand.

Either SpaceX is willing to make leaps of faith and assume applications will open up once they have hardware, or they built that raptor REALLY fast. Either way, a multi decade timeline may well be pessimistic.

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Gkirmathal

Gkirmathal

Posted
Posted (edited)
5 hours ago, RedKraken said:

I dont know how i missed this : https://www.reddit.com/r/spacex/comments/4wks2h/fanmade_mct_and_bfr_architecture_cad_and_math/

Apologies if it has already been posted... i've been away for a while.

This is very interesting. Though, I do not think Space-X will build this up scaled Dragon craft yet, especially if the current Dragon is capable of landing on Mars which they want to test in 2018 it was?

I think Musk will use the current Dragon design, as a base for a Mars landing capsule. MCT will be anyone's guess, although I hope Space-X is going to make it 'modular in design' (Dragon > hab control section | fuel propulsion section) and not follow Saturn's design paradigm of wanting to launch everything in one go thus limiting mission scale severely.

Edited by Gkirmathal
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KSK

KSK

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Posted

I'd have to dig out the reference but I did hear that Musk's current plan is for MCT - or at least the space travelling part of it - to be capable of landing on Mars and then returning to Earth. I presume that ISRU will be required for refueling after landing. Whether it's intended to enter Earth orbit for resupply and return to Mars, I don't know, but that would seem logical.

Basically a Big Flarping Spaceship with a Big Flarping Rocket to lift it into LKO. To be capable of landing and take-off from Mars under it's own power. Which sounds utterly awesome if they ever get it flying. I remain skeptical at this stage - Raptor engines are nice but there's a lot more to a spaceship than engines - although that $2B carbon fibre deal does suggest that SpaceX are committed and putting their money where their mouth is.

My inner space-cadet however, is squeeing it's little heart out.

 

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Nibb31

Nibb31

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Posted (edited)

One way to work out the minimum requirement for the BFS, you need to look for the dV requirements for each leg of the journey. Assuming it uses for the BFR and its own propellant load to get into LEO,  the other minimum requirements are:

LEO to Mars intercept and LMO to Earth intercept = 4260m/s

Mars surface to LMO =3800m/s

So assuming that the BFS is refueled in LEO and LMO by another BFS, and assuming it needs a few hundred m/s for propulsive landing and manoeuvering, the BFS needs to have at least 5000 m/s of dV with a payload of 80 metric tons.

In order to support 100 tons after landing, the dry mass of the vehicle will have to be at least 40 tons, including landing gear, structure, life support, heatshield, etc... (I think that's optimistic). So when you plug this data into the rocket equation with an average Isp of 320s, you get a total mass of 591 mt. Which is about the weight of a fully loaded A380.

To get the BFS to LEO; the BFR first stage is going to need to spend 4000 m/s and land. The Falcon 9 separates at Mach 10, which is 3430m/s, so it might be possible to push the envelope a bit more, but this means that the tanks of the BFS are empty when they reach orbit with its 80 ton payload. If you want to go anywhere, you need to fill it up. We've calculated that the BFS tanks are going to need to carry approximately 450 tons of propellant, and since the BFS has a 80 ton payload, you are going to need 6 BFS tanker flights to LEO and 6 to LMO to fill it up for each trip.

As for plugging the requirements of the BFR into the rocket equation, to get 4000m/s out of a 150-ton single stage with a 591-ton payload, you're rocket is going to weigh 2650 metric tons fully loaded. And that's without counting drag and gravity losses. Basically, that puts you in the Saturn V size category, with a BFR equivalent to the S-IC and S-II, and a BFS equivalent to the S-IVB and CSM/LM stack. The trick is in making the BFR and BFS reusable, which makes orbital refueling feasible.

Of course, to make this scheme work, SpaceX has yet to demonstrate:

  • 1st stage reusability
  • Powered landing from orbit
  • Orbital spacecraft reusability
  • Orbital refueling and propellant storage
  • Fast turnaround of the above
  • Long duration life support
  • Mars reentry
  • Mars powered landing
  • Automated ISRU and ground refueling
  • Mars launch
  • Reentry from Mars

That really is an awful lot of technology to be developed by a single company.

Edited by Nibb31
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magnemoe

magnemoe

Posted
Posted
2 hours ago, Gkirmathal said:

This is very interesting. Though, I do not think Space-X will build this up scaled Dragon craft yet, especially if the current Dragon is capable of landing on Mars which they want to test in 2018 it was?

I think Musk will use the current Dragon design, as a base for a Mars landing capsule. MCT will be anyone's guess, although I hope Space-X is going to make it 'modular in design' (Dragon > hab control section | fuel propulsion section) and not follow Saturn's design paradigm of wanting to launch everything in one go thus limiting mission scale severely.

Red dragon is an one way lander, it might contain an rocket for an sample return, else it will contain an lab and probably rovers. 
Think main benefit is that they can use used pods and existing technology a lot, this saves money even if the dragon is heavy.

One problem I see is to sterilize it to not bring microbes to Mars, this is an complex process and the dragon pod is not designed to be sterilized. 

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Frozen_Heart

Frozen_Heart

Posted
Posted
33 minutes ago, magnemoe said:

Red dragon is an one way lander, it might contain an rocket for an sample return, else it will contain an lab and probably rovers. 
Think main benefit is that they can use used pods and existing technology a lot, this saves money even if the dragon is heavy.

One problem I see is to sterilize it to not bring microbes to Mars, this is an complex process and the dragon pod is not designed to be sterilized. 

I think if they are planning humans on Mars then they aren't too fussed about contamination. You can't decontaminate humans.

(Well you can but....)

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Nibb31

Nibb31

Posted
Posted
7 minutes ago, kerbiloid said:

And what about colonial crew?

Red Dragon will not be manned. They will be using it for collecting data, development and prototyping.

When it comes to sending humans, concerns about contamination fly out of the window.

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Basto

Basto

Posted
Posted
7 hours ago, Rakaydos said:

The Raptor wasnt subsidized as an upperstage engine until recently, and it's already being sent to a test stand.

Either SpaceX is willing to make leaps of faith and assume applications will open up once they have hardware, or they built that raptor REALLY fast. Either way, a multi decade timeline may well be pessimistic.

From the sound of it MCT would need to be bigger and more powerful than SLS. Imagine what happens if SpaceX can build it for under $1B...  NASA is talking about a best case scenario of $2.5B for SLS and realistically it will probably be closer to $3B + (and that is without a Mars capable upper stage)

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tater

tater

Posted
Posted

The problem is financing something without a customer. NASA is certainly interested in Red Dragon as any Mars architecture requires the engineering knowledge that RD will gain, and it might take multiple flights to get right (something that would impact any current MCT design, as well).

Still, where is the money coming from? No bucks, no Buck Rogers.

 

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insert_name

insert_name

Posted
Posted
25 minutes ago, Basto said:

From the sound of it MCT would need to be bigger and more powerful than SLS. Imagine what happens if SpaceX can build it for under $1B...  NASA is talking about a best case scenario of $2.5B for SLS and realistically it will probably be closer to $3B + (and that is without a Mars capable upper stage)

SpaceX has already spent 2b on the carbon fiber alone. Given how big Elon wants to go, I suspect that it will cost more than the SLS.

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Frozen_Heart

Frozen_Heart

Posted
Posted
19 minutes ago, insert_name said:

SpaceX has already spent 2b on the carbon fiber alone. Given how big Elon wants to go, I suspect that it will cost more than the SLS.

To be fair that is setup cost, not cost per launch. The SLS has an estimate of 35 billion to develop until 2025.

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Rakaydos

Rakaydos

Posted
Posted (edited)
57 minutes ago, tater said:

The problem is financing something without a customer. NASA is certainly interested in Red Dragon as any Mars architecture requires the engineering knowledge that RD will gain, and it might take multiple flights to get right (something that would impact any current MCT design, as well).

Still, where is the money coming from? No bucks, no Buck Rogers.

 

I maintain my contention that the Falcon 9 costs SIGNIFICANTY less to build and lanuch than SpaceX is charging for it. Whatever the falcon 9 costs, they have no reason to price it too much lower than their competition-  it's a matter of finding a price where demand meets their production speed, any lower wastes demand they cant fill

Edited by Rakaydos
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Basto

Basto

Posted
Posted (edited)
52 minutes ago, insert_name said:

SpaceX has already spent 2b on the carbon fiber alone. Given how big Elon wants to go, I suspect that it will cost more than the SLS.

Actually that is a 2BN contract saying SpaceX will buy 2BN worth of carbon fiber from them. That does not mean they are spending 2BN on each rocket. 

Edited by Basto
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tater

tater

Posted
Posted (edited)
18 minutes ago, Rakaydos said:

I maintain my contention that the Falcon 9 costs SIGNIFICANTY less to build and lanuch than SpaceX is charging for it. Whatever the falcon 9 costs, they have no reason to price it too much lower than their competition-  it's a matter of finding a price where demand meets their production speed, any lower wastes demand they cant fill

SpaceX apparently has around 5000 employees (wiki). If the average wage is 40k a year (the median wage in the US is 51k), each launch right now includes about 18 Million $ of payroll. That can give us a lower limit on costs with a launch a month (2/mo and you can half that figure).

The whole Mars nonsense requires billions (with zero RoI), and even making 10s of millions per satellite launch, that's still chump change. The satellite market is finite, and in other threads people (including me) have done the math looking at the last few years of launches to see what % SpaceX could possibly take. The reality is that there are a small number of possible customers per year, and that is unlikely to change significantly.

 

Edited by tater
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