SpaceX BFR / MCT Discussion Thread

[fredinno]

20 hours ago, Findthepin1 said:

There was a thing called Keep Mars Red. It was a petition to the UN to make Mars a big national park and not let any terraforming happen. I can't find it on the net anymore. Does anyone know what happened to it?

Those people really have no idea.

Or they are dumb.

7 hours ago, Rakaydos said:

A number I find interesting... If we take the 100 tons to mars surface number as gospel, then the MCT could rebuild the entire ISS, on the SURFACE of MARS, in 4 launches.

 

That's a different enviroment, alright...

And the ISS only housed 6-7 people. 

[Findthepin1]

2 hours ago, fredinno said:

Those people really have no idea.

Or they are dumb.

And the ISS only housed 6-7 people. 

The ISS is mostly science and research space. Only a small bit is actually for the crew. The beds on the walls, the bathroom, food somewhere. Other than that, it's research and science equipment and labs unnecessary to the crew's survival. If you had 400 tons of only the ISS's crew-needed compartments you could fit many more people in a 400-ton ISS Mars compound. Maybe like 50 or something. 

By the way, there are 4444 topics in the forums right now. 

Edited December 18, 2015 by Findthepin1

[sojourner]

1 hour ago, Findthepin1 said:

 

By the way, there are 4444 topics in the forums right now. 

Um, Yay?

[fredinno]

1 hour ago, Findthepin1 said:

The ISS is mostly science and research space. Only a small bit is actually for the crew. The beds on the walls, the bathroom, food somewhere. Other than that, it's research and science equipment and labs unnecessary to the crew's survival. If you had 400 tons of only the ISS's crew-needed compartments you could fit many more people in a 400-ton ISS Mars compound. Maybe like 50 or something. 

By the way, there are 4444 topics in the forums right now. 

No, because MCT would probably also have to carry around life support equipment, and a LOT of cargo.

[DBowman]

BFR is also going to be a good Xtra Heavy launcher - right?

Orbital Solar Power is the only big $ space industry I can think of. I'd done some research a while ago (details in this post) and it looked to me that a proposal for Earth launched solar power (using SpaceX-ish launch costs I think) was already price competitive with existing on the ground installations. Also it seems like a good fit with Elon's whole Tesla thing, non CO2 power etc.

Making Orbital Solar as cheap as it can be is going to mean sourcing and using lots of 'resources from space'. Proving it out, beginning a roll out, and finally tooling up for space resource utilisation is going to require lots of earth launches - Space X would like lots of launches.

Mars might be a good source of some materials for the Orbital Solar industry, it's deltaV cheaper to supply LEO from Mars than from Earth and it might be easier to work with than the asteroids (no need to develop a lot of zero-g manufacturing tech). H20 and plastics (mylar mirror sheeting, structural elements) derived from the Mars atmosphere seem like things better done from Mars than Luna. One could launch 100 kg 'slugs' from a light hydrogen gas gun on the surface all the way to Earth, if your aim was 'good enough' they could aerocapture.

It's kind of the 'long way round' to Mars, but it would provide an economic motivation for being there.

[fredinno]

11 minutes ago, DBowman said:

BFR is also going to be a good Xtra Heavy launcher - right?

Orbital Solar Power is the only big $ space industry I can think of. I'd done some research a while ago (details in this post) and it looked to me that a proposal for Earth launched solar power (using SpaceX-ish launch costs I think) was already price competitive with existing on the ground installations. Also it seems like a good fit with Elon's whole Tesla thing, non CO2 power etc.

Making Orbital Solar as cheap as it can be is going to mean sourcing and using lots of 'resources from space'. Proving it out, beginning a roll out, and finally tooling up for space resource utilisation is going to require lots of earth launches - Space X would like lots of launches.

Mars might be a good source of some materials for the Orbital Solar industry, it's deltaV cheaper to supply LEO from Mars than from Earth and it might be easier to work with than the asteroids (no need to develop a lot of zero-g manufacturing tech). H20 and plastics (mylar mirror sheeting, structural elements) derived from the Mars atmosphere seem like things better done from Mars than Luna. One could launch 100 kg 'slugs' from a light hydrogen gas gun on the surface all the way to Earth, if your aim was 'good enough' they could aerocapture.

It's kind of the 'long way round' to Mars, but it would provide an economic motivation for being there.

"Competitive" Considering the cost of going to Space in the first place, I'm calling bull.

Also, transmission losses are insanely high in space, not to mention the times when Sun is blocking the Earth from Mars.

[DBowman]

@fredinno poke holes in they way I calced it if you like, I was surprised also so it'd be good to know what was wrong. The Topaz facility is in CA and now has data on how much power it produced and how much it cost, there is a link to the solar proposal with costings. One key thing is terrestrial solar power stations are rated at peak capability not achieved average, so a 10 GW station might really only be achieving 3 GW (night, cloud, season, etc).

Just to be clear I'm referring to proposals for solar collectors in lowish Earth orbits using microwave beams to transmit power to ground stations. I proposed here that Mars might be a good source of some materials from which to build these solar collectors in Earth orbit.

Edited December 18, 2015 by DBowman
typo

[Nibb31]

No way can orbital solar be competitive against ground solar. Even if ground solar had half the efficiency, you can simply double the surface at very little cost. The difference between putting a solar panel on the ground and putting one in space is several orders of magnitude, as is the cost of manufacturing one on the ground and manufacturing one in space, and that is without adding in the losses, environmental impact, and extra costs of the microwave transmission (which is something that has never been tested).

[DBowman]

Just in the interest of showing it's not as clear cut as it superficially appears.

Available energy:

• 100% 'in space' ( caveat: yes even an elliptical polar orbit will have some 'night' )
• 28% reaches the surface ( some NASA page caveat: not sure how they are accounting for rotation of the earth and vary atmosphere effective thickness, effective insolation could well be lower )
• 5% one sixth of the day is effectively available to generate, munging together things like angle of the sun in the sky, latitude, season etc. ( caveat: adding sun tracking hardware, one could locate the station somewhere 'more sunny' and pay terrestrial transmission costs - so you could increase the 5% by adding $$ )
• weather? seasons? effective thickness of atmosphere the light has to transit dawn vs noon? all may be only partially accounted for above

Ball park you'd expect 'space' to have 20 x as much energy to work with.

I think they expect microwave transmission to eat 50% - so space has 10 x as much 'energy at earth' to work with.

Solar thermal can use more of the spectrum than PV and large scale structures that stay sun tracking seem easier to build in orbit so maybe that can push 'space' back to 20 x or even 30 x 'energy at earth' to work with. 

Also worth noting that the full on proponents of this kind of thing want to avoid as far as possible bringing stuff from Earth, they envisage Luna solar powered rail guns (2.4 km/s vs 9.4 for earth).

Edited December 18, 2015 by DBowman

[Nibb31]

1 hour ago, DBowman said:

I think they expect microwave transmission to eat 50% - so space has 10 x as much 'energy at earth' to work with.

Those figures are as pessimistic as it gets, but who cares. Just build your ground-based solar farm in the desert and make it 10 times larger than your orbital solar farm. It will still cost 10 times less (at least).

Quote

Solar thermal can use more of the spectrum than PV and large scale structures that stay sun tracking seem easier to build in orbit so maybe that can push 'space' back to 20 x or even 30 x 'energy at earth' to work with. 

Also worth noting that the full on proponents of this kind of thing want to avoid as far as possible bringing stuff from Earth, they envisage Luna solar powered rail guns (2.4 km/s vs 9.4 for earth).

Which will cost how many times more than a conventional solar panel factory?

Edited December 18, 2015 by Nibb31

[Elthy]

For the price of a few rocket launches you could build/buy a whole factory for solar panels. Also microwave energy transmission from space is about as far away as fusion...

[Bill Phil]

9 hours ago, fredinno said:

"Competitive" Considering the cost of going to Space in the first place, I'm calling bull.

Also, transmission losses are insanely high in space, not to mention the times when Sun is blocking the Earth from Mars.

Transmission losses are high because most transmissions aren't focused beams. Most. Space solar power would use something like focused microwaves, but preferably with low enough energy that it doesn't fry you.

[Nibb31]

Good luck with that.

Either you put your orbital stations in GSO and you beam down to a single ground station 36000 below (say goodby to a "focused" beam) or they are in LEO and have to constantly repoint themselves to a different ground station, which is going to cause more loss.

Oh and those microwave array ground stations aren't going to be cheap either. I suspect that solar panels are way cheaper than just the microwave converters, let alone the space factories and orbital power stations.

But this should be moved to a separate topic because it really doesn't have much to do with BFR/MCT plans.

[Bill Phil]

8 minutes ago, Nibb31 said:

Good luck with that.

Either you put your orbital stations in GSO and you beam down to a single ground station 36000 below (say goodby to a "focused" beam) or they are in LEO and have to constantly repoint themselves to a different ground station, which is going to cause more loss.

Oh and those microwave array ground stations aren't going to be cheap either. I suspect that solar panels are way cheaper than just the microwave converters, let alone the space factories and orbital power stations.

But this should be moved to a separate topic because it really doesn't have much to do with BFR/MCT plans.

I'm not saying it's going to be done, or that it's practical. I'm saying it could be done. 

[Rakaydos]

6 hours ago, Nibb31 said:

Good luck with that.

Either you put your orbital stations in GSO and you beam down to a single ground station 36000 below (say goodby to a "focused" beam) or they are in LEO and have to constantly repoint themselves to a different ground station, which is going to cause more loss.

Oh and those microwave array ground stations aren't going to be cheap either. I suspect that solar panels are way cheaper than just the microwave converters, let alone the space factories and orbital power stations.

But this should be moved to a separate topic because it really doesn't have much to do with BFR/MCT plans.

Eh.. microwaves were chasen because of how easy there are to convert t electricity and back. While photovoltaics may get more bulk-discount, I still dont see them being cheaper than a microwave recever array.

[wumpus]

On 12/16/2015, 8:22:49, Findthepin1 said:

There was a thing called Keep Mars Red. It was a petition to the UN to make Mars a big national park and not let any terraforming happen. I can't find it on the net anymore. Does anyone know what happened to it?

According to Robert Heinlein, there were similar movements about not letting any footprints spoil the Moon.  Consider it rule 35: For any action, there is an equally reported on protest.

[Rakaydos]

So I just ran a few numbers based on that 100 tonne capacity, and it looks to me like the MCT Super Heavy Lifter could put an entire 80 thousand KM cable through the Earth Moon L1 for that much capacity. It's only 24000km past the lagrange, so it would probably need a separate counterweight launch, but that's the sort of infrastructure that would open uo the moon to cheap space-based exploitation.

Not Earth based exploitation, of course, but cheap water and metal for spacecraft that doesnt need to be hauled out of earth's gravity well/

[DBowman]

I don't really want to detour the thread too much so I'll try to 'wrap things up from me' wrt orbital solar power. As far as I can see orbital solar power is the most promising by far driver for space industrialization; endless growing demand, & growing pressure to curb CO2. I'd love to have a stronger driver but I cannot think of one.

The Topaz solar power station near San Diego (I think I recall) has a 'name plate' rating of 0.55 GW, it achieved 1100GHh which is a 126MW per hour and cost 2.5B.

SolarDisk proposal ( http://www.nss.org/settlement/ssp/library/1997-Mankins-FreshLookAtSpaceSolarPower.pdf ) put 6 satellites up for a total of 30 GW delivered power for 294 B 2015 USD.

So it takes 238 Topaz power stations to match the SolarDisk output; 595 B Topaz vs 294 B SolarDisk.

Now I'm sure there is something(s) wrong in the estimates for SolarDisk. However an existing solar power station cost and an orbital power station proposal being cost of the the same order of magnitude means it's not good enough to dismiss orbital out of hand on gut feel - there is no option but to dig into the details of the proposal for specific errors and miss-estimates. Probably the main determinant of these near term 'all from Earth' proposals is launch cost so more interesting than 'is this proposal cost effective now' is that there will be a $/kg launch cost which is the 'break even point', that's the price point that opens up large scale space industrialization.

[Red Fang]

So you are saying that the cable for a working, realistic, "we can start making it now" space lift cable weights on the order of 100 tons?  Am I reading this right? 

 

[Rakaydos]

2 hours ago, Red Fang said:

So you are saying that the cable for a working, realistic, "we can start making it now" space lift cable weights on the order of 100 tons?  Am I reading this right? 

A Lunar-Lagrange cable, yes, not an earth-geosynch one. It's longer but the stresses are lower.

100 tons is probably light if your including the whole space elevator assembily, but if you get extra capacity from not having to go interplanetary and land it on mars, I think a lunar  space elevtor as described by wikipedia is a reasonable MCT Superlifter payload.

 

Quote

One material that has great potential is M5 fiber . This is a synthetic fiber that is lighter than Kevlar or Spectra. ^[13]

According to Pearson, Levin, Oldson, and Wykes in their article The Lunar Space Elevator, an M5 ribbon 30 mm wide and 0.023 mm thick, would be able to support 2000 kg on the lunar surface (2005). It would also be able to hold 100 cargo vehicles, each with a mass of 580 kg, evenly spaced along the length of the elevator. ^[1]

Other materials that could be used are T1000G carbon fiber, Spectra 200, Dyneema (used on the YES2 spacecraft), or Zylon. All of these materials have breaking lengths of several hundred kilometers under 1g. ^[1]

 

Edited December 19, 2015 by Rakaydos

[ChrisSpace]

Again I think we're getting off-topic.

[Rakaydos]

On 12/13/2015 at 1:38 AM, Zucal said:

Mother of god. Leak/rumor from the NSF L2 forum.

RISE FROM YOUR GRAVE!

 

It's now mid 2016, and MCT is back in the rumormill after Elon's statement of intent for humans going to mars early next decade. there's a contract that has someone (I think DoD) helping pay to devlop Raptor-based upperstages for the falcon 9- the same tactic SpaceX used for the Falcon 1 to develope the Merlin engine for Falcon 9.

Bo Chika is breaking ground, Falcon heavy is behind schedual but should be launching in the next year, and the first Red Dragon will be sent up in 2 years, if all goes to plan.

And the final MCT reveal is supposed to be in 3 months. All insider information emphasizes it's ambitious scope. Secrecy consists of "If I told you you'd think we're crazy."

What a time to be alive.

[Ultimate Steve]

As far as going to Mars, we will eventually get there. I can't say when. it may be in ten years, It may be in two hundred years. I think we have a good chance with SpaceX and the MCT. It has been perhaps the most promising proposal yet, and as far as we know it is actually getting somewhere. Mr. Musk may not get the money for it right away, but he will keep making money off of satellite launches. He will eventually get the money. There are the technical challenges that were mentioned in this thread. Many people in this thread only have pointed out a lot of problems with this plan. Who is to say that the army of rocket scientists at SpaceX haven't thought of solutions to those problems? if a 150 post thread started in 2015 can find problems, and army of rocket scientists working for several years can fix them. I can guarantee there will be people with the resources and will to go to Mars. there are 8-ish billion people in the world. Even if 0.0001% of people want to and have the resources to go to Mars, that's still 8,000 people. There will be problems at Mars, I guarantee it, but as long as the MCT isn't wrecked the colonists can evacuate.

As for the space on the transport ship issue, It might be inflatable. Even if it isn't, some people live in smaller spaces.

My point is, eventually we will get there. It may not be soon, but we have a good shot with SpaceX's army of rocket scientists.

 

[Streetwind]

5 hours ago, Rakaydos said:

It's now mid 2016, and MCT is back in the rumormill after Elon's statement of intent for humans going to mars early next decade. there's a contract that has someone (I think DoD) helping pay to devlop Raptor-based upperstages for the falcon 9- the same tactic SpaceX used for the Falcon 1 to develope the Merlin engine for Falcon 9.

Bo Chika is breaking ground, Falcon heavy is behind schedual but should be launching in the next year, and the first Red Dragon will be sent up in 2 years, if all goes to plan.

And the final MCT reveal is supposed to be in 3 months. All insider information emphasizes it's ambitious scope. Secrecy consists of "If I told you you'd think we're crazy."

What a time to be alive.

We have provisional launch targets too, now. 2022 for the first BFR launch, 2024 for the first humans riding MCT to Mars.

Audacious schedule? Definitely. But hey, that's what it is, for the tiem being!

[sojourner]

This thread is going to get real fun in september.