Author Topic: MCT Speculation and Discussion Thread 4  (Read 503232 times)

Offline guckyfan

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Re: MCT Speculation and Discussion Thread 4
« Reply #1500 on: 01/29/2016 10:07 AM »
I think after several cargo mission, first with FH and then MCT. When MCT successfully land on Mars. First crew will arrive without specified return day. There task will be prepare infrastructure and ask for additional resources in  preparation of infrastructure for return trip. Setup ice collection and build and maintain devices to create fuel,build tank for fuel. At the moment finishing task and prepare rocket  for return trip some of the crew will start their trip back to Earth. I think when first crew will arrive there  will be not enough fuel to bring them back, they have to build their "return ticket".

That was exactly my thougt too. However Elon Musk has stated that return fuel will be ready when the first crew arrives. Which means everything will need to be done by robots.

Offline mfck

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Re: MCT Speculation and Discussion Thread 4
« Reply #1501 on: 01/29/2016 10:39 AM »
Blah,, blah... blah
...
...

Undesrtood!
If you were to do a 3D model of the Depot it would just be a 2D (x,y) skeletal frame that is repeated into the third (z) dimension. Below is a sketch of the forward frame for one berth. The small circle is a "pad" for connecting to the nose of the MCT and the large circle is an imaginary volume representing one berth where one MCT is docked. The frames are connected by beams of a certain length in the z dimension. Then this 3D image is duplicated side-by-side to the right to make 5 additional berths until they join on the left side of the first berth. Voila!

Is this?

http://imgur.com/a/KJRna
Nice skill, BSenna.

How many hardpoints per BFS on this structure do you guys envision?

Offline Ionmars

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Re: MCT Speculation and Discussion Thread 4
« Reply #1502 on: 01/29/2016 01:09 PM »
Now that BSenna has shown us what the propellant depot will look like in Reply #1497 above, we will need to make some adjustments.

First a note about adaptability. When I first proposed this type of depot last year it had an international flavor. I used the imaginary company "LEO Logistics International" as the entity to build and operate the Depot. This was to indicate that this should be an international project and not restricted to any one country. My feeling is that if we are to make the human species interplanetary, no nation and no people will be left behind. This may mean that vehicles constructed by other countries would share the use of the Depot. Because SpaceX is now involved in US military contracts it may not be the best entity to implement this project. Whatever international entity implements this project, it needs an adaptable design that accommodates different vehicles, within reason.

What is the main difference between an openly shared design and a one-country design? It is secrecy. SpaceX must keep under wraps its spacecraft designs and its extensive test results so as to maintain its competitive edge in rocketry. ITAR regulations also play a role. So the Depot should be able to service a vehicle at the Depot without requiring too much inside information: a service station that doesn't need to know what's under the hood.

What are the compatibility requirements for the Depot to service the MCT or a similar craft?
1. The craft must utilize LOX and LCH4 as fuel.
2. It must have a diameter compatible to the diameter of the Spacex MCT diameter. Today we think that will be about 15 m, but a range up to 19 m is probably doable. This is because the vehicle lies within a V-shaped berth without actually touching the framework; the only contact is a set of four flexible-length latches that extend from the framework to the vehicle.
3. Two Latch points on the exterior of the vehicle must be within the reach of the two robotic arms that pull the vehicle into its berth.
4. Four latch points on the exterior that are within reach of the four flexible-length latches.
5. Accessible fuel ports. The current Depot design assumes a capsule shape at the end and fuel ports through the nose cone. Alternatively, if MCT takes on an biconic shape with TPS on one side then fuel ports will be located on the dorsal (non-TPS) side) and propellant lines will need to be located along the interior cavity of the Depot.
6. Vehicle length within a range that the depot can accommodate. At this time I think about 60 m length is appropriate. If a vehicle is longer than the depot it will stick out at the aft end, but no harm there.  If it is shorter, it just needs to be within reach of the robotic arms and latches.

As much as possible we want the Depot design to adapt to the MCT design rather than vice-versa. Other than that we are "go" for launch and service.
 
* Mars' orbit: a convenient service station for an asteroid-sized spaceship en-route to Ceres. *

Offline docmordrid

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Re: MCT Speculation and Discussion Thread 4
« Reply #1503 on: 01/29/2016 02:00 PM »
An international depot presupposes everyone using the same fuel, which doesn't look like the case at all. Assuming ULA gets ACES tankers off the ground they look to supply LH2. SpaceX is of course going  methane. The Russian Fenix looks  to be a methane "Zenit" (Sputnik News) and clustered for a heavy, but do we know what they'll use once in space if they even use tankers? China??
« Last Edit: 01/29/2016 02:05 PM by docmordrid »
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Offline CraigLieb

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Re: MCT Speculation and Discussion Thread 4
« Reply #1504 on: 01/29/2016 02:29 PM »
Crazy idea number 854:
Could a fuel depot like this dip a "very long" stiff hose into the atmosphere, pump air up, and make fuel by processing CO2 and/or capturing methane?
Granted it might take a really long time, but is it even technically possible? I assume the power supply to run this would have to be solar. since if it is anything else, you use more fuel than you make most likely.
Colonize Mars!

Offline The Amazing Catstronaut

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Re: MCT Speculation and Discussion Thread 4
« Reply #1505 on: 01/29/2016 02:37 PM »
How heavy would the hose and pumps be? How much drag would it add? How many decades would it need to be running for to manufacture significant fuel?
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Offline Ionmars

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Re: MCT Speculation and Discussion Thread 4
« Reply #1506 on: 01/29/2016 02:41 PM »
An international depot presupposes everyone using the same fuel, which doesn't look like the case at all. Assuming ULA gets ACES tankers off the ground they look to supply LH2. SpaceX is of course going  methane. The Russian Fenix looks  to be a methane "Zenit" (Sputnik News) and clustered for a heavy, but do we know what they'll use once in space if they even use tankers? China??
Good point. Can't please everybody, but BE-4 methane engine will be used for something. What?
* Mars' orbit: a convenient service station for an asteroid-sized spaceship en-route to Ceres. *

Offline docmordrid

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Re: MCT Speculation and Discussion Thread 4
« Reply #1507 on: 01/29/2016 02:44 PM »
The first stage of Vulcan and Blues own launcher, and their uppers use LH2. I haven't seen anything about a BE-4 Vac.
« Last Edit: 01/29/2016 02:46 PM by docmordrid »
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Offline Ionmars

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Re: MCT Speculation and Discussion Thread 4
« Reply #1508 on: 01/29/2016 02:44 PM »
Crazy idea number 854:
Could a fuel depot like this dip a "very long" stiff hose into the atmosphere, pump air up, and make fuel by processing CO2 and/or capturing methane?
Granted it might take a really long time, but is it even technically possible? I assume the power supply to run this would have to be solar. since if it is anything else, you use more fuel than you make most likely.
No, it isn't feasible. But I do like crazy ideas.
* Mars' orbit: a convenient service station for an asteroid-sized spaceship en-route to Ceres. *

Offline Ionmars

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Re: MCT Speculation and Discussion Thread 4
« Reply #1509 on: 01/29/2016 02:50 PM »
The first stage of Vulcan and Blues own launcher, and their uppers use LH2. I haven't seen anything about a BE-4 Vac.
Ok, so not compatible with a MCT depot.
* Mars' orbit: a convenient service station for an asteroid-sized spaceship en-route to Ceres. *

Offline Robotbeat

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Re: MCT Speculation and Discussion Thread 4
« Reply #1510 on: 01/30/2016 12:14 AM »
No word of a depot from SpaceX.

Depots have a big advantage with hydrogen since hydrogen wants to boil-off really bad, and it takes fancy equipment like a mult-layer sunshield and an active cooler to stop that. But both methane and oxygen are space-storable, meaning with the right type of paint and by keeping your tanks out of direct sunlight (point the long way, butt to the Sun), you can get passive zero boil-off.

So I really don't think SpaceX is planning a depot. But things change.
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Offline nadreck

Re: MCT Speculation and Discussion Thread 4
« Reply #1511 on: 01/30/2016 12:23 AM »
A depot for the MCT vs fuel transfer from a tanker could offer: slow rotational ulage, helium depot services, liquid nitrogen heat sink for propellant during transfer. If you made such a depot you could probably include liquid hydrogen support at a cost if someone were willing to pay that cost, though it would add complexity.
It is all well and good to quote those things that made it past your confirmation bias that other people wrote, but this is a discussion board damnit! Let us know what you think! And why!

Offline Pipcard

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Re: MCT Speculation and Discussion Thread 4
« Reply #1512 on: 01/30/2016 12:26 AM »
No word of a depot from SpaceX.

Depots have a big advantage with hydrogen since hydrogen wants to boil-off really bad, and it takes fancy equipment like a mult-layer sunshield and an active cooler to stop that. But both methane and oxygen are space-storable, meaning with the right type of paint and by keeping your tanks out of direct sunlight (point the long way, butt to the Sun), you can get passive zero boil-off.

So I really don't think SpaceX is planning a depot. But things change.
Well, if an MCT is going to act as the second stage of the BFR, it has to refuel in orbit. And if people launch on the MCT, they can't wait for multiple tankers (i.e. MCTs acting as tankers) to come and fill it up.
« Last Edit: 01/30/2016 12:30 AM by Pipcard »

Offline QuantumG

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Re: MCT Speculation and Discussion Thread 4
« Reply #1513 on: 01/30/2016 12:28 AM »
Well, if an MCT is going to act as the second stage of the BFR, it has to refuel in orbit. And if people launch on the MCT, it can't wait for multiple tanker MCTs to come and fill it up.

Why not? They're going to be in space for the whole trip to Mars, what's a few more weeks in LEO?  (Speaking of which, do we know if the refuelling is to be in LEO or somewhere else?)

Jeff Bezos has billions to spend on rockets and can go at whatever pace he likes! Wow! What pace is he going at? Well... have you heard of Zeno's paradox?

Offline Pipcard

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Re: MCT Speculation and Discussion Thread 4
« Reply #1514 on: 01/30/2016 12:32 AM »
Well, if an MCT is going to act as the second stage of the BFR, it has to refuel in orbit. And if people launch on the MCT, it can't wait for multiple tanker MCTs to come and fill it up.

Why not? They're going to be in space for the whole trip to Mars, what's a few more weeks in LEO?  (Speaking of which, do we know if the refuelling is to be in LEO or somewhere else?)
Waiting around in LEO when you're supposed to go to Mars is wasteful for the life support systems.
« Last Edit: 01/30/2016 12:32 AM by Pipcard »

Offline QuantumG

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Re: MCT Speculation and Discussion Thread 4
« Reply #1515 on: 01/30/2016 12:34 AM »
Waiting around in LEO when you're supposed to go to Mars is wasteful for the life support systems.

Really? Seems like a much cheaper option than depots. Don't get me wrong, I'm all for depots - but because they imply a different architecture to "biggest rocket evar".
Jeff Bezos has billions to spend on rockets and can go at whatever pace he likes! Wow! What pace is he going at? Well... have you heard of Zeno's paradox?

Offline Robotbeat

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Re: MCT Speculation and Discussion Thread 4
« Reply #1516 on: 01/30/2016 12:37 AM »
Waiting around in LEO when you're supposed to go to Mars is wasteful for the life support systems.

Really? Seems like a much cheaper option than depots. Don't get me wrong, I'm all for depots - but because they imply a different architecture to "biggest rocket evar".
I don't get the impression that Musk is planning a big rocket just to have a big rocket, but that the size will be perfectly well-justified based on the total IMLEO needed for full-scale MCT operations (on the order of a million tons per year IMLEO).
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Offline BSenna

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Re: MCT Speculation and Discussion Thread 4
« Reply #1517 on: 01/30/2016 01:16 AM »
What if...ionmars'll gonna hate that... The fuel carriers 2, 3 and 4 transfer The fuel directly to carrier 1 one carrier each time, then the 1 transfers to the incoming MCT? Is that feasible?

Concerning a fuel depot standard, soon there will be an international standard discussion, then anyone that intends to build something, will do it using The ISO.
« Last Edit: 01/30/2016 02:11 AM by BSenna »

Online launchwatcher

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Re: MCT Speculation and Discussion Thread 4
« Reply #1518 on: 01/30/2016 01:49 AM »
What if...ionmars'll gonna hate that... The fuel carriers 2, 3 and 4 transfer The fuel directly to carrier 1 each time, then 1 transfers to the incoming MCT? Os that feasible?
I was just about to suggest exactly that.   One tanker *is* the depot; you end up doing N launches to put a completely full tanker in orbit, then launch a crew+cargo MCT, fill it from the full tanker, and off we go..

alternatively, you could daisy-chain:
launch tanker #1
launch tanker #2 to rendezvous with #1; transfer from #1 to #2; land #1
launch tanker #3 to rendezvous with #2; transfer from #2 to #3; land #2
(repeat until there is a full tanker in orbit)

launch cargo/crew vessel to rendezvous with tanker #N; transfer fuel, land #N

With that scheme, you do more pumping, but all tankers spend about the same amount of time in orbit..

Offline guckyfan

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Re: MCT Speculation and Discussion Thread 4
« Reply #1519 on: 01/30/2016 03:29 AM »
What if...ionmars'll gonna hate that... The fuel carriers 2, 3 and 4 transfer The fuel directly to carrier 1 each time, then 1 transfers to the incoming MCT? Os that feasible?
I was just about to suggest exactly that.   One tanker *is* the depot; you end up doing N launches to put a completely full tanker in orbit, then launch a crew+cargo MCT, fill it from the full tanker, and off we go..

alternatively, you could daisy-chain:
launch tanker #1
launch tanker #2 to rendezvous with #1; transfer from #1 to #2; land #1
launch tanker #3 to rendezvous with #2; transfer from #2 to #3; land #2
(repeat until there is a full tanker in orbit)

launch cargo/crew vessel to rendezvous with tanker #N; transfer fuel, land #N

With that scheme, you do more pumping, but all tankers spend about the same amount of time in orbit..

My idea was that tankers reach their design limit of launches and landings. They then get a complete overhaul of the RCS and do their last launch to stay in orbit as depots.

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