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#51 2018-06-21 11:05:32

Void
Member
Registered: 2011-12-29
Posts: 2,442

Re: Space X forging ahead with BFR

I am short on time just now, but although I did not think that I had a notion of what to do about the questions I asked recently, to a degree time and the comments of other members have given me some notions.  Maybe just a trial balloon.

I am thinking of the Kilopower units and the first two ships which are to fly prior to the 4 later ships.

In this link is shown a depiction of a BFS that can deliver a satellite to LEO.  It has a sort of a nose end flip door.
http://www.spacex.com/mars
So still another variety of BFS.

So I will get to it.  I suggest that for the two first ships, one or both would have Kilopower reactors built into it.  In order to radiate heat to the Martian sky, perhaps it would be necessary to have a nose end flip door.

This eliminates the need to unload the reactors, and deploy them to the surface, and allows the reactors to be integrated into the ships electrical system as launched from Earth.  I understand that there will be a weight penalty for doing this, but I propose to have these ships do some very useful work while they are there and before and after the four other ships arrive.

The useful work they can do, involves limitations on machine animation, and the problem of latency between Earth and Mars.  No humans will be present, and we don't expect to provide Sci-Fi level type robotic equipment.  I don't believe that that exists in a reliable form, at this time, and we are constrained on weight anyway.

It is interesting to study the English language.

Couch Potato suggests a vegetable (The couch potato is rather motionless).
Power Plant, also suggests something that is planted but produces power.

Animated suggests "Animal".

So, from my point of view these two ships if they are both outfitted with Kilopower rectors will be "Planted" and not very "Animated" after they land on the surface of Mars.  They will not be able to deploy and connect solar power plant, except in limited fashion, and they will not be able to mine or transport water ice.

So, what can they do?  They can process Martian atmosphere into products that may be useful.  O2, and CO primarily, prior to and during the presence of the four later BFS's.

So, they each have an Oxygen tank and a fuel tank that is now idle.  Why not put them to use?

So the first act would be to burn the remaining Methane into Water Vapor and I presume CO2, and then purge/vent the fuel tank to the Martian atmosphere.  Collect the water vapor created into ice and store it somewhere on the ship(s).

Then of course I intend that O2 will be created from the Martian atmosphere and stored into the Oxygen tank (Refrigeration required).
Then of course I intend that the CO will be created from the Martian atmosphere and stored into the Fuel tank (Refrigeration required).

Before you have a hemorrhage, let me say I don't intend to use the CO directly as fuel in a rocket that burns CH4.  Going to CO is just the first step in producing CH4 later.

So, presuming the Four later ships land on Mars, and somehow if necessary can also hop over to the first two if they landed far away in a dust storm, the crew(s) would have One or Two, previous landed ships that would already be provisioned and electrified by Planted Nuclear Method.  The time interval between the first two and later 4 landings having been put to productive use.

The question arises, can the Methane Fuel Tank(s) accommodate liquid CO?  I don't know.
Refrigeration for the cryogenic liquids?  Well you have Kilopower on the ships, and ship structures which may serve as radiators.  Impossible/Impractical?  Well that's what I am wondering.

As for consumption of consumables of the crew(s) when they land, I suggest that the primary shelter be associated/connected to the two Kilopowered prior ships.  That way the Oxygen in the tanks can be consumed for breathing.  The power from the Kilopower reactors of course to provide heat and electricity for the crews comfort/survival.  As for food, that being frozen or dried in nature could be stockpiled in a prior manner in the two early ships.  Enough to weather a global dust storm.

As for pipelines, if it is possible to get all of the ships located optimal to each other, then a pipeline for the CO, to the other ships which will deploy solar arrays in an animated fashion using the crews mobility and that of their motorized equipment.

......

I will deviate a bit.  I am wondering about the four BFS's being able to hop about.  This would be desired, if they began to topple for instance, I presume if they could thrust to a hop then that would require an AI system activating it and fuel reserves.

Hopping would also be useful, if indeed the four ships had to land in a dust storm, and originally landed too far away for optimal base operations.

AI would have to be very good so that it did not make a mistake and think that the ship was toppling when it was not.

Fuel reserves would be necessary on any ship that would hop.

......

Here is a link which suggests Fuel Tankers, and Depots.  I cannot say that it is the Holy "Gospel" of BFS's.  But it is an encouragement to me.
https://www.nextbigfuture.com/2017/11/s … iness.html

Quote:

An orbital propellant depot is a cache of propellant that is placed in orbit around Earth or another body to allow spacecraft or the transfer stage of the spacecraft to be fueled in space.

One variation of the "Tanker" would have it arriving to LEO empty.  My hope would be that it could have less mass devoted to engines.  Just getting the shell to LEO would be the purpose.  Would it be disposable?  For the initial Mars operation then likely yes.  It would be a One Off more or less, and might not need other frills such as a heat shield.

There are three possible uses I might propose for it.
1) As a booster to boost the passenger and maybe cargo ships to Mars, conserving the on board fuel and Oxygen to make the hopping notion possible upon landing on Mars.
2) As a bring along tank, and redundant thruster system, same idea.
3) As a fuel depot per O.F. to orbit Mars.  Then either you insert it to Martian orbit per Thrusters, Aerocapture, Ballistic Capture.
Some combination of the three, or use of two or just one.

The value of #3 would be to reduce the initial size of the Power Plant(s) that you would need initially on the surface of Mars, making that task easier, but complicating the return mission.

And that is about it for now.

Not that I will react badly publically, but I will not like it much if this post is ignored, and subsequent posts seem to ignore it.  That is a bit of an insult.  I would rather be told at least that it was a set of ideas with flaws, and would like to be able to try to fix the problems, or admit that something else is needed.

I will be traveling, so out of touch for a while.
Done.

Last edited by Void (2018-06-21 11:51:23)


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#52 2018-06-21 17:31:29

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 13,056

Re: Space X forging ahead with BFR

The satelite BFR launcher is simular to the shuttle operation the wing lets on the back end is to make it have a sled like guild in the upper atmospher to be something like a lifting body.

Have consitently suggested recycling reuse of any thing that goes to mars multiple times as this reduces the cargo demand on follow up flights and the empty tanks are just one of those items.

We have talked abit about the hopper flight rockets in the past using the CO to make it not wasted if we have an excess.

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#53 2018-06-21 20:46:32

Void
Member
Registered: 2011-12-29
Posts: 2,442

Re: Space X forging ahead with BFR

Thanks for the reply.

I think the strengths of this proposal are many.

For one thing when your crew arrives on Mars, these ships could have been cooking up Oxygen and CO from the atmosphere, and filling the tanks.

The Kilowatt nuclear reactors should sill have plenty of life in them, so you would have a power grid on those ships to run electric tools and lighting even during a dust storm.

The small amount of ice stored would be a bonus for life support.  (This water would have come from burning off the residual Methane in the propulsion system, prior to converting that fuel tank to a liquid CO reservoir).

Immediately having the stored LOX and CO would allow you to fuel rovers designed to burn that fuel.

The CO can be a pathway to food and higher power fuels, such as Methane and Biofuels.

But of course for that you will need crew and their machinery active mining to moisture from ice and or soil, and to some how involve the Hydrogen from the water with the CO, and possibly solar energy.

You could have an advantage over the standard Sabatier Reaction:
https://en.wikipedia.org/wiki/Sabatier_reaction
Quote:

The Sabatier reaction or Sabatier process was discovered by the French chemist Paul Sabatier in the 1910s. It involves the reaction of hydrogen with carbon dioxide at elevated temperatures (optimally 300–400 °C) and pressures in the presence of a nickel catalyst to produce methane and water. Optionally, ruthenium on alumina (aluminium oxide) makes a more efficient catalyst. It is described by the following exothermic reaction:

CO2 + 4H2 --------------> CH4 + 2H2O

I am not a chemist, but....

If you start with CO + 2H2 and add heat and possibly pressure, I might think we would get CH4 + H2O???  Is that about right???

At that point Heat could come from various sources.  Solar Cells, KilloPower, or "THE DREADED SOLAR CONCENTRATING MIRROR!!!".  Heliostats I am afraid.  Don't know which is the best.

Pressure I would be imposed with an electric motor/pump system as appropriate I suppose.

Here is a microbial pathway to fuels from Carbon Monoxide.
https://www.sciencedaily.com/releases/2 … 131742.htm
Ethanol

Here is an interesting biological pathway with a microbe:
https://scienceblog.com/9417/microbe-pr … -monoxide/
In this case H20 + CO causes a microbe to generate Hydrogen.

Here is commentary that indicates that Martian life (If it exists) must be rare because the CO in the Martian atmosphere is not being tapped.
https://www.newscientist.com/article/21 … -untapped/
Quote:

Martian life must be rare as free energy source remains untapped

This has become a better test for life than Oxygen in an atmosphere for extra solar planets.  Oxygen in an atmosphere might come from non-biological sources.  However if Carbon Monoxide is in an atmosphere, it indicates that life is not eating it.  That suggests that life is rare or non-existing.


https://www.researchgate.net/publicatio … rmentation

So the point being that Carbon Monoxide and H20 or H2 can be a source of fuels (Including Methane), and chemicals and foods through fermentation.

......

As mentioned above the Martian atmosphere contains tiny amounts of both Carbon Monoxide and Oxygen produced I presume by photolysis.

I do not propose to tap those reserves until much later.

I do propose that the first two ships may be bringing nuclear power and "Planted" automation to process CO2 into O2 and CO.

When the crews arrive, then an expanded solar energy component and ice mining would allow for further chemistry, such as the manufacture of CH4 and fermented foods.

While Insitu produced solar is a good goal after that, also a good goal is to tap the tiny amount of O2 and Carbon Monoxide in the Martian atmosphere.  That will require some kind of mechanical gill.  I cannot guarantee that it can be done, but it is well worth looking at, as it is obvious what a good building block Carbon Monoxide can be for a chemical industry.  And if you can get the dissolved Oxygen out of the atmosphere then that is great as well.

But if the gill proves impossible, then of course Solar only until Insitu nuclear fission can be arranged as well.

Done.

Last edited by Void (2018-06-21 21:31:09)


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#54 2018-06-22 04:04:26

louis
Member
From: UK
Registered: 2008-03-24
Posts: 3,939

Re: Space X forging ahead with BFR

Void -

According to this, a single Kilopower Unit produces up to 10Kwe of electric power. So for two it's up to 20Kwe.  You aren't going to manufacture much with just 20 Kws.

https://en.wikipedia.org/wiki/Kilopower



Void wrote:

Thanks for the reply.

I think the strengths of this proposal are many.

For one thing when your crew arrives on Mars, these ships could have been cooking up Oxygen and CO from the atmosphere, and filling the tanks.

The Kilowatt nuclear reactors should sill have plenty of life in them, so you would have a power grid on those ships to run electric tools and lighting even during a dust storm.

The small amount of ice stored would be a bonus for life support.  (This water would have come from burning off the residual Methane in the propulsion system, prior to converting that fuel tank to a liquid CO reservoir).

Immediately having the stored LOX and CO would allow you to fuel rovers designed to burn that fuel.

The CO can be a pathway to food and higher power fuels, such as Methane and Biofuels.

But of course for that you will need crew and their machinery active mining to moisture from ice and or soil, and to some how involve the Hydrogen from the water with the CO, and possibly solar energy.

You could have an advantage over the standard Sabatier Reaction:
https://en.wikipedia.org/wiki/Sabatier_reaction
Quote:

The Sabatier reaction or Sabatier process was discovered by the French chemist Paul Sabatier in the 1910s. It involves the reaction of hydrogen with carbon dioxide at elevated temperatures (optimally 300–400 °C) and pressures in the presence of a nickel catalyst to produce methane and water. Optionally, ruthenium on alumina (aluminium oxide) makes a more efficient catalyst. It is described by the following exothermic reaction:

CO2 + 4H2 --------------> CH4 + 2H2O

I am not a chemist, but....

If you start with CO + 2H2 and add heat and possibly pressure, I might think we would get CH4 + H2O???  Is that about right???

At that point Heat could come from various sources.  Solar Cells, KilloPower, or "THE DREADED SOLAR CONCENTRATING MIRROR!!!".  Heliostats I am afraid.  Don't know which is the best.

Pressure I would be imposed with an electric motor/pump system as appropriate I suppose.

Here is a microbial pathway to fuels from Carbon Monoxide.
https://www.sciencedaily.com/releases/2 … 131742.htm
Ethanol

Here is an interesting biological pathway with a microbe:
https://scienceblog.com/9417/microbe-pr … -monoxide/
In this case H20 + CO causes a microbe to generate Hydrogen.

Here is commentary that indicates that Martian life (If it exists) must be rare because the CO in the Martian atmosphere is not being tapped.
https://www.newscientist.com/article/21 … -untapped/
Quote:

Martian life must be rare as free energy source remains untapped

This has become a better test for life than Oxygen in an atmosphere for extra solar planets.  Oxygen in an atmosphere might come from non-biological sources.  However if Carbon Monoxide is in an atmosphere, it indicates that life is not eating it.  That suggests that life is rare or non-existing.


https://www.researchgate.net/publicatio … rmentation

So the point being that Carbon Monoxide and H20 or H2 can be a source of fuels (Including Methane), and chemicals and foods through fermentation.

......

As mentioned above the Martian atmosphere contains tiny amounts of both Carbon Monoxide and Oxygen produced I presume by photolysis.

I do not propose to tap those reserves until much later.

I do propose that the first two ships may be bringing nuclear power and "Planted" automation to process CO2 into O2 and CO.

When the crews arrive, then an expanded solar energy component and ice mining would allow for further chemistry, such as the manufacture of CH4 and fermented foods.

While Insitu produced solar is a good goal after that, also a good goal is to tap the tiny amount of O2 and Carbon Monoxide in the Martian atmosphere.  That will require some kind of mechanical gill.  I cannot guarantee that it can be done, but it is well worth looking at, as it is obvious what a good building block Carbon Monoxide can be for a chemical industry.  And if you can get the dissolved Oxygen out of the atmosphere then that is great as well.

But if the gill proves impossible, then of course Solar only until Insitu nuclear fission can be arranged as well.

Done.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#55 2018-06-22 07:03:18

kbd512
Member
Registered: 2015-01-02
Posts: 2,113

Re: Space X forging ahead with BFR

If the experiments done by Lockheed-Martin scales linearly, then solar power alone, without batteries, is more than sufficient for LOX/LCH4 and LOX/LH2.  Forget about using megawatts of power at night.  It's not necessary or desirable from a mass standpoint.  Take more food and water.  You'll need that to survive.  You don't need megawatts of power when using modern electronics and life support equipment.

Keep the habitat powered by its own dedicated solar array and batteries that don't out-gas or explode.  This fanciful idea that you don't have to monitor the electrical power systems, so long as you're not using nuclear, is pure unadulterated BS.  There is no such thing as a megawatt class power system that doesn't require monitoring.  Anyone who thinks otherwise is blissfully unaware of what can and will go wrong, no matter where the power is coming from.

Keep the reactor in standby mode, where it's warmed up and can ramp up to full power in minutes, just in case someone does something unbelievably stupid with the batteries that power the life support equipment.  At 1kW or less of thermal power, the reactor is ready to operate when required, but not in a condition where losing all of the coolant loops could present any sort of thermal power rejection problem.  A reactor scram at that power level is almost like flipping a switch.  Fission stops in seconds.

Since I know all actual objections to using KiloPower have to do with safety and the potential for a melt-down, I'll post some of the documents that show the modeling and testing done to assure desired operation here:

Space Nuclear Reactor Engineering

KiloPower Project - KRUSTY Experiment Nuclear Design

KRUSTY Design and Modeling

If you think the people who design and build these things just have blind faith in anything, you'd be wrong.  Everything, and I do mean everything they can think of, gets tested.  They intentionally try to destroy the reactor just to see what will happen.  All models and assumptions are actually tested to ensure they agree with reality.  If they don't, then the engineers go back to the drawing board and re-test, as required.

When they tell you how much these things weigh, how big they'll be, how hot they get, and how much radiation they'll produce, they're not talking out their rear ends.  They create ANSYS models, which they then turn into manufactured hardware, and that's what gets tested.  ANSYS can tell you with high precision how much something will weigh when it's made from known materials.  KiloPower is metal blocks and tubes with a working fluid sealed into the tubes.  For a reactor this small, a 10% scale model can tell you with excellent fidelity what a slightly larger device will weigh, how much thermal power you get, and what the results of a thermal system failure will be.  The actual observed data agree very well with the model and that gives engineers confidence that the slightly dimensionally larger core model will behave in much the same way with small incremental increases in thermal output levels.

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#56 2018-06-22 09:58:17

Void
Member
Registered: 2011-12-29
Posts: 2,442

Re: Space X forging ahead with BFR

Interesting information.  Of course I am not at all versed in it.  But I do understand a situation where a "Planted" robot might collect and upgrade materials for later human use.  I see it as being high value,  Nuclear fission as the starting power source seems to fit into that puzzle.


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#57 2018-06-22 10:42:56

kbd512
Member
Registered: 2015-01-02
Posts: 2,113

Re: Space X forging ahead with BFR

If people freak out this much over a nuclear reactor with one control to operate and two temperatures and two pressures to watch, wait until they see what the controls for a megawatt class power station look like.  It'll blow their minds.  There's nothing about KiloPower that's remotely as complicated as a solar power array of the scale required to produce rocket propellants.  People probably should freak out over how complicated the array and propellant plant will be to maintain.  It's not a "replace the dust filter on your A/C unit every 6 months" proposition.

Full time jobs:
1. monitoring everything
2. repairing and maintaining the equipment
3. keeping everything clean

12 crew members seems more plausible than 6, so 3 shifts of 4 crew members each.

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#58 2018-06-27 18:46:00

louis
Member
From: UK
Registered: 2008-03-24
Posts: 3,939

Re: Space X forging ahead with BFR

Not sure if I posted this before. Don't think so.

https://www.youtube.com/watch?v=7G_ChY0Tsxw&t=17s

He has a very positive view of how things are progressing, which of course is very much in line with the way I see it as well.

He points how far advanced Space X is on BFR engines, propellant tank and body, and also raising money for the BFR development.


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#59 2018-08-31 16:58:47

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 13,056

Re: Space X forging ahead with BFR

One point that GW has made meantion of is the refuel on orbit issues to which its a problem that Space X has not been doing any research into.
That is not the case for Nasa which is doing just that. Ironing out the difficulties of moving fluids in space

Fluid flows downhill - at least it does on Earth. Fluid movement becomes much more complicated in space, and that creates challenges for systems that rely on pumping fluids around for thermal control, engine propellants and other functions.

An investigation aboard the International Space Station studies moving fluids with the power of magnets instead of using pumps with mechanical moving parts. Ferrofluids contain small iron-oxide particles that can be magnetized. For the PAPELL experiment, researchers use an electromagnetic field to manipulate and move these ferrofluids in a variety of different conditions. Cameras and sensors monitor the movement of the fluids across grids of electromagnets and through pipes.

"Mechanical components always pose a risk of failure, a problem that needs to be avoided on space missions, especially long ones," says Franziska Hild, one of the team of 30 students of the University of Stuttgart's Small Satellite Student Society (KSat e. V.) that developed and is conducting the investigation. "Use of a non-mechanical pump extends the lifetime of the system, allowing its use on long-term missions for thermal or propellant management."

Reliable, efficient pumping and other fluid transportation tasks are particularly important in the design of next-generation space vehicles. The ability to move fluids smoothly from one place to another in microgravity could eliminate many potential wrinkles in space exploration.

The exact behavior of a liquid under magnetic influence in microgravity is part of the investigation, adds Manfred Ehresmann, another of the investigators. "Currently, we are uncertain whether microgravity will increase or decrease the magnetic pump's performance. Easier movement in microgravity may aid movability of individual droplets, or hinder our manipulation capability by increasing the distances to the electromagnets."

In addition to advancing the technology for design of this new class of pumps in space, PAPELL may help solve other space-based fluid transport problems, says investigator Kira Grunwald. A low-wear, low-vibration, and low-maintenance pumping system could improve the performance and expected lifetime of space stations, satellites and space telescopes.

Pumps that require little maintenance and have extended operational lifetimes also have many potential applications on Earth, such as for pumping water in remote areas. The lower noise level of magnetic pumps also improves safety and comfort in the workplace, whether in space and on the ground.

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#60 2018-09-07 17:27:53

louis
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From: UK
Registered: 2008-03-24
Posts: 3,939

Re: Space X forging ahead with BFR

Looks like the South Texas site is being readied for 2019 hop tests.


https://www.teslarati.com/spacex-boca-c … test-prep/

Great news! smile


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#61 2018-09-07 18:52:48

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 13,056

Re: Space X forging ahead with BFR

So much for a composite tank....

Boca-Chica-LOX-tank-install-071118-nomadd-1-991x557.jpg

100,000-gallon liquid oxygen tank

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#62 2018-09-08 16:27:32

louis
Member
From: UK
Registered: 2008-03-24
Posts: 3,939

Re: Space X forging ahead with BFR

That was a joke right?  This is the ground supply feed or storage tank for the BFR...well if not I've misunderstood something! smile

SpaceNut wrote:

So much for a composite tank....

https://cdn.teslarati.com/wp-content/up … 91x557.jpg

100,000-gallon liquid oxygen tank


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#63 2018-09-08 19:55:13

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 13,056

Re: Space X forging ahead with BFR

Yes, you caught me, as it look just like the ones from Blue Origin’s New Glenn LOX and liquid methane (LNG) propellant tanks. But where is the remaining items to even make liquid Oxygen on the site...

I happen to drive by a Liquid nitrogen plant and know just how large that is on a small scale....

lobster_tank_tcm138-384303_w1024_n.jpg

The exhaust heat radiators are huge but I am not finding any images yet.
This one is simular and you can see the radiators just above the the left of the tanks.
l_20170208_91510_6130_tcm19-398282.jpg

Why do they put Lox in gallons for the tank when we are looking at the mass as the issue for launch.

http://www.uigi.com/o2_conv.html

100,000 gallons = 432 mt or 302,500 cu m of a tank.

https://www.calculator.net/volume-calculator.html


https://www.linde-engineering.com/en/im … 466459.pdf

l_20170208_91510_6130_tcm19-398282.jpg

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#64 2018-09-09 16:43:52

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 13,056

Re: Space X forging ahead with BFR

Solving for numbers...
https://www.nextbigfuture.com/2018/04/s … -tool.html
The bfs seems to be approximate 30 meters for tank area maybe 36 with the remaining height for the crew cabin making the total height 48 meters tall for the 2nd stage. Dry mass of 85 T.... pressurized volume of 825 m3 (29,100 cu ft), with up to 40 cabins, large common areas, central storage, a galley, and a solar storm shelter for Mars missions.

bd6123f4d4dc3b01725dabe9bca3cf34-1024x564.png

CH4 is 240 T while the Lox is 860 T for the total fuel load of 1,100 T.

Total ship is 106 m with that making the first stage is 58 meters tall. Total vehicle mass is 4,400 fully loaded with the second stage total is 1335 with payload leaving the first stage to be 3,065 T fuel and dry structure.

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#65 2018-09-09 18:20:22

louis
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From: UK
Registered: 2008-03-24
Posts: 3,939

Re: Space X forging ahead with BFR

1100 tons for total fuel/propellant load.  Will try and remember that figure.  But do they need all that 1100 tons to get back home to Earth? I think I read somewhere it was somewhat less than that...

SpaceNut wrote:

Solving for numbers...
https://www.nextbigfuture.com/2018/04/s … -tool.html
The bfs seems to be approximate 30 meters for tank area maybe 36 with the remaining height for the crew cabin making the total height 48 meters tall for the 2nd stage. Dry mass of 85 T.... pressurized volume of 825 m3 (29,100 cu ft), with up to 40 cabins, large common areas, central storage, a galley, and a solar storm shelter for Mars missions.

https://www.nextbigfuture.com/wp-conten … 24x564.png

CH4 is 240 T while the Lox is 860 T for the total fuel load of 1,100 T.

Total ship is 106 m with that making the first stage is 58 meters tall. Total vehicle mass is 4,400 fully loaded with the second stage total is 1335 with payload leaving the first stage to be 3,065 T fuel and dry structure.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#66 2018-09-09 21:23:19

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 13,056

Re: Space X forging ahead with BFR

With the 2 stage design and maximizing the payload just as the Falcon 9 heavy design there is little fuel remaining in the stage to do anything but the deorbit burn and a final firing to slow the ship at the very end.

Falcon 9 Heavy 1,420,788 kg (including payload mass) total launch mass for a 63,800 kg payload is achieved when the rocket flies a fully expendable launch profile, not recovering any of the three first-stage boosters. With just the core booster expended, and two side-boosters recovered, Musk estimates the payload penalty to be around 10%, which would still yield over 57 tonnes of lift capability to LEO.

I do think the penalty is higher such that payload would drop to say 50,000 kg.

BFR is to be 4,400,000 kg for 150,000 kg payload, So we are talking about 3 sets of heavy strapped together in order to do the same function....

1,421 t x 3 = 4,263 Mt total launch mass.....

SpaceX determined that the mass needed for a re-entry heat shield, landing engines, and other equipment to support recovery of the second stage was at that time prohibitive, and indefinitely suspended their second-stage reusability plans for the Falcon line but will do experimental tests on recovering one or more second-stages in order to learn more about reusability to inform their new, much-larger, BFR launch vehicle development process.

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#67 2018-09-09 22:20:37

kbd512
Member
Registered: 2015-01-02
Posts: 2,113

Re: Space X forging ahead with BFR

SpaceNut,

I wonder if lighter expendable components would be cheaper to use to achieve delivered tonnage targets.  For example, the reusable Titanium grid fins are spectacularly expensive because they're reusable.  How cheaply could composite tanks and grid fins with minimal to no insulation be made if they only had to survive ascent?

Will it turn out that only recovering the engines and computers is cheaper than complete reusability?  The experiments being done by ULA should tell us which system / method ends up reducing launch costs the most.  If we're just throwing away epoxied carbon composites and the price of composite materials continues to fall while robotic fabrication methods reduce construction time and therefore cost, expending the parts of the rocket that can be rapidly and robotically manufactured may be the optimal solution if cost is the primary consideration.  Or perhaps not.  We have to actually get both companies to complete development and then accumulate some flight history with their tech to figure that out.

If it takes a week to repair, clean, and test reusable Lithium-Aluminum propellant tanks, but new expendable composite tanks that require no maintenance can be fabricated, pressure tested, and delivered to the launch pad in less than a week, then perhaps no standing army of airframe maintainers is required to refurbish metal propellant tanks.  As airframes age, cracking from fatigue and corrosion begins to exact its toll, as it pertains to keeping the airframe airworthy, eventually becoming as hideously expensive as maintaining old engines.

Airliners don't have to clean and pressure test fuel tanks between refueling and don't store their oxidizer.  LOX aggressively attacks most lightweight metals.  Most parts of the airframe not related to the engine aren't subjected to the tremendous forces and temperature deltas that rockets are, either.

I guess time will tell us which method maximizes the utility of reusable components without increasing the cost to maintain them to parity with expendable parts.

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#68 2018-09-10 17:06:37

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 13,056

Re: Space X forging ahead with BFR

The first stage of a Falcon9  requires about 25 to 30% of the stages fuel in order for it to be reuseable. The second stage is totally unknown as they have never tried to recover one. If the recoverable second stage was to use the same biased numbers then out of the posted fuel allotment for the stage being 1100 would leave as expendable fuel in the stage of 275 to 330 left over to put into the crew or cargo unit for mars in addition to the 150 tons that would be payload. If that stage is expendable then the mass of the stage will drop to allow even more fuel to be maintained from the boost to orbit as well as an increase in payload. You can also change the design to drop the heat resistant materials and lots more in favor of making it lighter and expendable.

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#69 2018-09-14 09:52:53

Oldfart1939
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Registered: 2016-11-26
Posts: 1,548

Re: Space X forging ahead with BFR

In a SpaceNews.com article today, SpaceX President Gwynne Shotwell stated that the first test hops of the spaceship portion of BFS have slipped from late 2019 into 2020. This seems to be the normal progression of events for the company. "There's many a slip twixt the cup and the lip."

https://spacenews.com/spacex-to-announc … ion-plans/

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#70 2018-09-14 10:22:13

Oldfart1939
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Registered: 2016-11-26
Posts: 1,548

Re: Space X forging ahead with BFR

The mission slippage reported in my earlier post seems to be "Normal Musk development time." In the comment section over at SpaceNews.com, many there are excited over the representation of the "new BFS" bearing 7 engines in place of 6, and addition of a canard type set of fins. I remain highly skeptical of the timeline for the first BFS cargo missions to Mars by 2022. Still need to develop the orbital refueling system/techniques, and have a demonstration mission for landing something--not just something this huge--but anything. An awful lot of things to accomplish in 3 1/2 years, Elon!

Last edited by Oldfart1939 (2018-09-14 10:23:14)

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#71 2018-09-14 14:11:34

louis
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From: UK
Registered: 2008-03-24
Posts: 3,939

Re: Space X forging ahead with BFR

Au contraire mon amis...

Here's the quote:

"While Musk said earlier this year those tests could begin in the first half of 2019, Shotwell suggested recently that date had slipped. “I think we’ll be hopping that second stage next year, late next year,” she said during a panel at DARPA’s D60 conference Sept. 6 near Washington."

Next year is 2019. And late 2019 is definitely second half of 2019 and perhaps last quarter. So, not 2020 as you claim.  To fast on the trigger there!

Obviously the chances of a 2022 launch for Mars are receding but I don't think have been eliminated entirely.


Oldfart1939 wrote:

In a SpaceNews.com article today, SpaceX President Gwynne Shotwell stated that the first test hops of the spaceship portion of BFS have slipped from late 2019 into 2020. This seems to be the normal progression of events for the company. "There's many a slip twixt the cup and the lip."

https://spacenews.com/spacex-to-announc … ion-plans/


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#72 2018-09-14 15:26:46

louis
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From: UK
Registered: 2008-03-24
Posts: 3,939

Re: Space X forging ahead with BFR

I'd placed this on another thread earlier, but might as well transfer it here.  

Space X ready to kickstart lunar tourism...great news.

The BFR hop flights look they have already slipped into late 2019, so the 2022 Mars mission is looking more precarious but lunar tourism will certainly put money in the Space X coffers.

"While Musk said earlier this year those tests could begin in the first half of 2019, Shotwell suggested recently that date had slipped. “I think we’ll be hopping that second stage next year, late next year,” she said during a panel at DARPA’s D60 conference Sept. 6 near Washington."

Also of interest to the rocketeers here:

"An illustration posted with the tweet about the lunar mission announcement appeared to show minor changes to the BFR spaceship design since Musk’s last major speech about it last September at the International Astronautical Congress (IAC) in Australia. Those changes include larger tail fins and seven engines in its base, versus six. Musk, ased on Twitter if the illustration represented the current design of the BFR, responded simply with “Yes.”  "

https://spacenews.com/spacex-to-announc … ion-plans/


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#73 2018-10-02 19:22:57

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 13,056

Re: Space X forging ahead with BFR

Since you found offense to this post in what you stated was a surface use of BFR only I have moved it to this one since its about getting to mars.

The ships use verticle for landing and gravity of the planets but in space we will be creating artificial gravity to keep the crew healthy and that could be tumbling end over end or rotating in some designs...which would also change what we are calling floors and ceilings....

Of course there is also the impact on plumbing through out the ship under those same conditions of use.

A crew that takes 8 months to get to mars will be weakened and the trip back will be even more sever on them after the long period of time at what be marginally mars gravity. This crew will be very weakened and near unable to move under earth gravity if they make it through the high G entry....

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#74 2018-10-03 04:25:37

louis
Member
From: UK
Registered: 2008-03-24
Posts: 3,939

Re: Space X forging ahead with BFR

Offence is a bit strong! I just didn't think it was relevant as AG is not part of the Space X project design. However, I doubt an in flight AG system (which is going to involve some kind of spinning) is going to be compatible with conditions on the Mars surface. So the same objection applies as regards "dual use" of BFR for flight and surface habitat.

There is a little evidence that an 8 month flight will cause severe weakness and there is every reason to expect 0.38 G to be recuperative.  Exercise, medicine, surface weight suits and careful crew selection (selecting those who suffer minimal bone and muscle loss in zero G) can all minimise the risk. But I would agree that a 2.5 year mission to Mars and back will likely be close to the limit of our current abilities.

SpaceNut wrote:

Since you found offense to this post in what you stated was a surface use of BFR only I have moved it to this one since its about getting to mars.

The ships use verticle for landing and gravity of the planets but in space we will be creating artificial gravity to keep the crew healthy and that could be tumbling end over end or rotating in some designs...which would also change what we are calling floors and ceilings....

Of course there is also the impact on plumbing through out the ship under those same conditions of use.

A crew that takes 8 months to get to mars will be weakened and the trip back will be even more sever on them after the long period of time at what be marginally mars gravity. This crew will be very weakened and near unable to move under earth gravity if they make it through the high G entry....


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#75 2018-10-04 02:36:54

elderflower
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Registered: 2016-06-19
Posts: 929

Re: Space X forging ahead with BFR

Propositions about low gravity remain untested. It wouldn't be difficult to test, at least in part, using a modest rotating satellite with rats. The fact that it hasn't been done at all indicates to me that NASA hasn't the least intention of sending people to Mars.

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