Author Topic: MCT Speculation and Discussion Thread 4  (Read 502609 times)

Offline Paul451

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Re: MCT Speculation and Discussion Thread 4
« Reply #1320 on: 01/06/2016 06:19 AM »
A human rated MCT needs a launch abort system.
The LAS will probably eject the crew compartment only, not the big engines and fuel tanks. So
A mct\bfs will be built of two seperate parts - the propultion module and the utility module.
The propultion module is practically the BFR's 2nd stage and the utility module will be mission specific.
That's how I see it. Does it makes sence?

This has come up before. The LAS-compartment will need to, in effect, be an independent spacecraft, capable of re-entry and landing.

In which case, why not just launch your humans on the "LAS" itself, and launch the BFS separately?

That way you're not trying to design a BFS that can safely split into two separate parts mid-launch, while still functioing as a single reentry vehicle (which, IMO, is going to be harder than simply having two independent vehicles.) It also means that the unmanned BFS can sit in LEO being refuelled before launching to Mars, without your passengers on board getting in the way and using up resources. At the 11th hour, the passengers are launched on the smaller crew-shuttle to the BFS.

The crew-shuttle is not only smaller than the full BFS. If you ferry the passengers up in groups of ten or twenty, it could be smaller still.

[Aside: My gut feeling is that if the BFS is the second stage on the BFR, then Musk will just have the whole BFS abort.]

Offline philw1776

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Re: MCT Speculation and Discussion Thread 4
« Reply #1321 on: 01/06/2016 05:13 PM »
Maybe it's just me but I read this as Elon saying that the BFR/MCT (now called BFS) is a 2 part entity which I interpret as that stage 2 IS the BFS.  A booster rocket (stage one with lots of engines) and a spaceship (stage 2).

"Well, there's two parts of it—there's a booster rocket and there's a spaceship. So the booster rocket's just to get it out of Earth's gravity because Earth has quite a deep gravity well and thick atmosphere, but the spaceship can go from Mars to Earth without any booster, because Mars's gravity is weaker and the atmosphere's thinner, so it's got enough capability to get all the way back here by itself. It needs a helping hand out of Earth's gravity well. So, technically, it would be the BFR and the BFS." As in "Big frakking Spaceship."

http://www.gq.com/story/elon-musk-mars-spacex-tesla-interview?utm_source=10370

This also pretty much says that the spaceship part needs to have the delta V capability for Mars surface to Earth (debatable Earth surface or LEO, maybe either).  That means more than small couple hundred mT propellant tanks.

Whether this is the best approach or the final architecture remains to be seen but it would be surprising to see a radical departure from this in the short term assuming there's a spring 2016 BFR/MCT information release.
« Last Edit: 01/06/2016 05:18 PM by philw1776 »
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Online guckyfan

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Re: MCT Speculation and Discussion Thread 4
« Reply #1322 on: 01/06/2016 05:39 PM »
Maybe it's just me but I read this as Elon saying that the BFR/MCT (now called BFS) is a 2 part entity which I interpret as that stage 2 IS the BFS.  A booster rocket (stage one with lots of engines) and a spaceship (stage 2).

It's not just you. Though still even now some people disagree.

Offline dror

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Re: MCT Speculation and Discussion Thread 4
« Reply #1323 on: 01/06/2016 06:52 PM »
Maybe it's just me but I read this as Elon saying that the BFR/MCT (now called BFS) is a 2 part entity which I interpret as that stage 2 IS the BFS.  A booster rocket (stage one with lots of engines) and a spaceship (stage 2).

"Well, there's two parts of it—there's a booster rocket and there's a spaceship. So the booster rocket's just to get it out of Earth's gravity because Earth has quite a deep gravity well and thick atmosphere, but the spaceship can go from Mars to Earth without any booster, because Mars's gravity is weaker and the atmosphere's thinner, so it's got enough capability to get all the way back here by itself. It needs a helping hand out of Earth's gravity well. So, technically, it would be the BFR and the BFS." As in "Big frakking Spaceship."

http://www.gq.com/story/elon-musk-mars-spacex-tesla-interview?utm_source=10370

This also pretty much says that the spaceship part needs to have the delta V capability for Mars surface to Earth (debatable Earth surface or LEO, maybe either).  That means more than small couple hundred mT propellant tanks.

Whether this is the best approach or the final architecture remains to be seen but it would be surprising to see a radical departure from this in the short term assuming there's a spring 2016 BFR/MCT information release.
Well, still,

It does not say whether the BFS is monolitic or modular.
It doesn't mention LEO refuel before mars injection and we know that from previos qoutes.
It does not say 'direct mars surface to earth' only 'from Mars to Earth without any booster' , so refuel in mars orbit is also an option.
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Online guckyfan

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Re: MCT Speculation and Discussion Thread 4
« Reply #1324 on: 01/06/2016 09:23 PM »
It does not say whether the BFS is monolitic or modular.

True. I bet on modular, have argued for that for a while.

Quote
It doesn't mention LEO refuel before mars injection and we know that from previos qoutes.

LEO refuel is a given. It is a requirement, no way to reach the target performance without it. And it was mentioned. There was talk about refuelling before leaving for Mars.

Quote
It does not say 'direct mars surface to earth' only 'from Mars to Earth without any booster' , so refuel in mars orbit is also an option.

Not an option, much too complex early on. Also not required. Much smaller payload back to earth was stated. That does not need Mars orbit refuelling. Though fuel ISRU on Phobos or Deimos is one of my pet ideas. It has potential to make things a lot easier. But certainly not a requirement and not part of the initial plan.

Offline Impaler

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Re: MCT Speculation and Discussion Thread 4
« Reply #1325 on: 01/06/2016 09:55 PM »
Point is that the only thing definitively ruled out by Musk statement as a single-stage-to-mars vehicle.  Your interpreting every statement by Musk as total confirmation of your speculation but it's far from that.

Offline Paul451

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Re: MCT Speculation and Discussion Thread 4
« Reply #1326 on: 01/06/2016 10:33 PM »
Maybe it's just me but I read this as Elon saying that the BFR/MCT (now called BFS) is a 2 part entity which I interpret as that stage 2 IS the BFS.  A booster rocket (stage one with lots of engines) and a spaceship (stage 2).
"Well, there's two parts of it—there's a booster rocket and there's a spaceship. but the spaceship can go from Mars to Earth without any booster, because Mars's gravity is weaker and the atmosphere's thinner, so it's got enough capability to get all the way back here by itself. It needs a helping hand out of Earth's gravity well. So, technically, it would be the BFR and the BFS." As in "Big frakking Spaceship."

While I suspect your interpretation is correct, Musk wasn't talking to us, nor answering a question about whether there's a second stage. He was being very general and non-technical.

Hence, it's still possible that the "booster rocket" is a two stage launcher.

For example, "Well, there's two parts of it - there's a booster rocket, called Falcon 9, and there's a spaceship, called Dragon. The spaceship can return from orbit on its own. The velocity for deorbiting is less, so it's got enough capability to dock with ISS, then get back to Earth by itself. It just needs a helping hand out of Earth's gravity well."

[Edit: I mean, if we're going to be pedantic, a "booster rocket" should mean it's a side-mount. Ie, BFS will fire it's engines from launch to orbit, with a large "booster" to assists while it's fuel heavy. 1.5STO.]
« Last Edit: 01/06/2016 10:37 PM by Paul451 »

Offline philw1776

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Re: MCT Speculation and Discussion Thread 4
« Reply #1327 on: 01/06/2016 11:43 PM »
I agree that those other interpretations are not definitively ruled out, hence "Maybe it's just me..."
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Online guckyfan

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Re: MCT Speculation and Discussion Thread 4
« Reply #1328 on: 01/07/2016 07:54 AM »
Point is that the only thing definitively ruled out by Musk statement as a single-stage-to-mars vehicle.  Your interpreting every statement by Musk as total confirmation of your speculation but it's far from that.

No, it is the other way around. I base my speculations on statements by SpaceX, you don't. Your concepts may be completely valid, I don't deny that. They are in conflict with SpaceX however.

Offline TomH

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Re: MCT Speculation and Discussion Thread 4
« Reply #1329 on: 01/07/2016 05:04 PM »
Point is that the only thing definitively ruled out by Musk statement as a single-stage-to-mars vehicle.  Your interpreting every statement by Musk as total confirmation of your speculation but it's far from that.

No, it is the other way around. I base my speculations on statements by SpaceX, you don't. Your concepts may be completely valid, I don't deny that. They are in conflict with SpaceX however.

Sorry guckyfan, ISTM that you take even the slightest off-the-cuff statements and hyperbolic tweets that Musk makes as always being absolute literal truth, with no margin for error. IMO you take some things far too literally and as absolutisms.

Offline Lars-J

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Re: MCT Speculation and Discussion Thread 4
« Reply #1330 on: 01/07/2016 05:15 PM »
Point is that the only thing definitively ruled out by Musk statement as a single-stage-to-mars vehicle.  Your interpreting every statement by Musk as total confirmation of your speculation but it's far from that.

No, it is the other way around. I base my speculations on statements by SpaceX, you don't. Your concepts may be completely valid, I don't deny that. They are in conflict with SpaceX however.

Sorry guckyfan, ISTM that you take even the slightest off-the-cuff statements and hyperbolic tweets that Musk makes as always being absolute literal truth, with no margin for error. IMO you take some things far too literally and as absolutisms.

You either A) take him and the folks at SpaceX by their word(s), or B) you do mental gymnastics to warp them to fit your own predetermined architecture. The sensible thing in this thread - based on its name - is to be closer to option A. If you prefer option B, there are other Mars related forums on this site.

Offline raketa

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Re: MCT Speculation and Discussion Thread 4
« Reply #1331 on: 01/07/2016 10:17 PM »
This is my idea of MCT, focusing on survival on all critical parts of Mars Journey, since there will multiple MCT on the way and they will not probably use 100 people before base is build and they could help each others.

Offline philw1776

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Re: MCT Speculation and Discussion Thread 4
« Reply #1332 on: 01/08/2016 06:12 PM »
How does the MCT escape module land on Mars w/o killing everyone as it slams into the regolith?  Chutes ain't gonna git 'er done there.
Just make your upper stage like an airliner, either it gets there or you have no more worries at tax time, ever.
« Last Edit: 01/08/2016 06:13 PM by philw1776 »
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Offline raketa

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Re: MCT Speculation and Discussion Thread 4
« Reply #1333 on: 01/08/2016 07:44 PM »
MCT Escape system will have enough power to leave booster/MCT Engine and slow down using atmosphere and land using rocket engines.
On Earth more aerobraking
On Mars fight less gravity

Offline Stardhingy

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Re: MCT Speculation and Discussion Thread 4
« Reply #1334 on: 01/08/2016 09:03 PM »
How does the MCT escape module land on Mars w/o killing everyone as it slams into the regolith?  Chutes ain't gonna git 'er done there.
Just make your upper stage like an airliner, either it gets there or you have no more worries at tax time, ever.

That's my opinion as well. Build it stout. No matter how many Russian dolls of escape pods you have, the last one includes passengers and rocket fuel, if it lights up everyone dies.
« Last Edit: 01/08/2016 09:05 PM by Stardhingy »

Offline Robotbeat

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Re: MCT Speculation and Discussion Thread 4
« Reply #1335 on: 01/08/2016 11:34 PM »
How does the MCT escape module land on Mars w/o killing everyone as it slams into the regolith?  Chutes ain't gonna git 'er done there....
...they will if you add a retro-rocket to them, like this:
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Offline stoker5432

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Re: MCT Speculation and Discussion Thread 4
« Reply #1336 on: 01/09/2016 03:30 AM »

and you land on a prepared surface.
Robotbeat, you have mentioned this 'prepared surface' in several posts. How this would be accomplished?

NASA has some ideas so maybe SpaceX will get some advice from from them.

http://www.nasa.gov/content/landing-pads-being-designed-for-extraterrestrial-missions

Exactly, Dr. Phil is the guy I was thinking of.

Here's some quotes from the article:

"Robotic landers would go to a location on Mars and excavate a site, clearing rocks, leveling and grading an area and then stabilizing the regolith to withstand impact forces of the rocket plume," Mueller said. "Another option is to excavate down to bedrock to give a firm foundation. Fabric or other geo-textile material could also be used to stabilize the soil and ensure there is a good landing site."

...
""We've tested several types of materials and it seems that basalt regolith mixed with polymer binders hold up well," Metzger said."

Sulfer concrete might be a good solution too.

http://www.citylab.com/tech/2016/01/mars-build-house-concrete-sulfur-study/423288/?utm_source=yahoo


Offline Patchouli

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Re: MCT Speculation and Discussion Thread 4
« Reply #1338 on: 01/13/2016 08:09 AM »
I wonder if it could be used for monolithic domes?
https://en.wikipedia.org/wiki/Monolithic_dome

We have extensive discussion of these things in the general Mars section. I suggest we keep it there and keep this thread closer to MCT. Sulphur concrete was not discussed there yet, I believe, but discussion should be there.

Just a short note, It has higher tensile strength than concrete and should enable domes to some extent. People tend to forget that tensile strength is what is required to build pressurized domes. Not so much compressive strength.


Offline TomH

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Re: MCT Speculation and Discussion Thread 4
« Reply #1339 on: 01/13/2016 04:23 PM »
...they will if you add a retro-rocket to them, like this...

That chute will help some after the heat shield reaches terminal velocity, but in an atmosphere that's 0.0059 X the density of Earth's atmosphere at the surface, you're still going to have a lot more velocity to overcome with retrorockets than that pallet has. Your gravity losses will be less, but you still have the inertia to kill off.

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