totm nov 2023 SpaceX Discussion Thread

[Rakaydos]

Fuel is cheap. You don't need a 95% ratio, you just need infrastructure to make and store fuel. "Growing it there", to return to the Hawaii metaphor.

Just because porkbarrel politics didn't LET us colonize the moon in the 70s, doesn't mean it was impossible. Nixon killed Apollo Applications before he was kicked out of office, Regan gutted the Space Transport System to just the orbital shuttle portion.

But SpaceX doesn't need to stretch a 6 year program to 12 years to milk all the money it can from a government contract, like Boeing. Quite the opposite- they built three prototypes and two facilities in half a year using 5% of the company resources. THAT is how you open up the solar system.

[kerbiloid]

15 minutes ago, Rakaydos said:

Fuel is cheap.

When you need to spend 95% of cargo to deliver 5%, it doesn't matter if it is cheap, it is practically not wise.
Also who said it is cheap? To produce this fuel you have to spend energy and pollute the atmosphere, you need supporting infrastructure, and so on.

Spoiler

Let's tell about the "cheap fuel" to Gretchen, lol.

18 minutes ago, Rakaydos said:

return to the Hawaii metaphor.

When you have reached Hawaii, you need nothing except Hawaii anymore. (Well, I guess.)

When you reach the Moon or the Mars, you still need everything from the Earth.
So, when the trip will take just 1 tank of those four, and several days, this will be a deal, until that it's a feat.

21 minutes ago, Rakaydos said:

Just because porkbarrel politics didn't LET us colonize the moon in the 70s

I still can't see anything deserving a permanent lunar base, leave alone "settlement",
In 1970s it was pure fantasy.

23 minutes ago, Rakaydos said:

But SpaceX doesn't need to stretch a 6 year program to 12 years to milk all the money it can from a government contract, like Boeing. Quite the opposite- they built three prototypes and two facilities in half a year using 5% of the company resources.

it needs profit, so it's in even worse position than Boeing.

24 minutes ago, Rakaydos said:

THAT is how you open up the solar system.

That's how we'll see another one such thing:
 

Spoiler

(Replace the wings with multiraptors)

 

[Technical Ben]

Yeah. It's sad but true. If the economy can stretch to tourists flying around the moon, it may stretch to tourists staying on the moon. Governments may sponsor "bases" for governmental reasons (shows of strength). But physically or economically, there is nothing in space we would pay for.

 

Asteroids for materials gets around the cost of land/mining rights. But if the cost is there, places could drop the price of mining rights, and then SpaceX would lose all those launches/asteroid returns.

 

An economy is a strange thing, and you cannot second guess it. The Sproose Goose never really "flew", and even the big double decker aircraft are being retired at times. Sometimes it works out (international air flight) sometimes it does not (channel Hovercraft ferries ).

[Wjolcz]

1 hour ago, kerbiloid said:

Once landed six times.
Any settlers there?

Got to LEO with Vostok and Mercury. Any stations there? If you want bigger things in space you need to use bigger rockets. Not impossible.

1 hour ago, kerbiloid said:

The same aboul sailships. None of them can reach the Moon.

Imagine, it's going to the Moon.

I really don't get this one. Guess I'm not smart enough. Starship is not a sailship, neither was Saturn V.

[tater]

 

[sevenperforce]

15 hours ago, Wjolcz said:

On the SS LES topic: what happens to the 2nd stage when the 1st stage fails? Has anything like this ever happened? IIRC the last two F9 failures involved the second stage being faulty. To me it seems kind of logical that if the first stage goes boom boom the stage falls apart and the smaller bits slow down much faster than the second heavier stage. Unless the bits get sucked up into the lower pressure zone behind the ship, but even then if the engine spool time is super fast those might get deflected or obliterated before they reach the upper stage.

Lower-stage failure in flight is pretty benign, as rocket accidents go. Plus, Starship is quite aerodynamic. The real challenge is zero-zero abort, where you not only need enough thrust to escape the fireball on the pad (think Amos-6 but in the lower stage), but you need to get far enough away from the affected zone to land safely.

15 hours ago, Wjolcz said:

The worst case scenario that (I think) can happen is when the fuel tank raptures and releases all the pressure. But even then it would first spread and then ignite. How hot is the CH4 and Ox reaction? Since SS is made out of steel (with chilly fuel in it) and the engine nozzles are, well, heat resistand engine nozzles they should be fine, no? Besides, isn't the CH4 stored in relatively low pressure?

Three atmospheres, so yeah, it's not bad. The big risk for a non-hypergolic vehicle like Superheavy is that the fuel and oxidizer mix before ignition. That's where you get a bomb. Worst-case scenario for a pad emergency would be if the inner bulkhead ruptures without igniting and the LOX and CH₄ start to mix slowly. Then you're stuck on top, without enough thrust to get free of the pad, waiting for three thousand metric tonnes of accidental high-explosive gel to detonate. The largest non-nuclear explosion in history, the July 3 1969 N-1 failure, occurred with only 15% of the RP-1 burning. If just half of the propellant in Superheavy formed an explosive gel and detonated, it would produce an explosion four and a half times greater than the N-1's, roughly a third the yield of the Little Boy bomb dropped on Hiroshima.

This threat of mixing-then-detonating is one of the reasons why early rocket designers preferred hypergolics. Not only are hypergolics easier to design engines for, but because they ignite on contact they will never be able to mix-and-explode like cryos. The Titan II launch vehicle used for Gemini was fueled with hypergolics, which contributed to the designers being okay with ejector seats rather than a full-envelope LES as with the Atlas that launched John Glenn et al during Mercury.

15 hours ago, Wjolcz said:

Edit: even worse worst case scenario: the whole thing violently turns to the side and snaps in half. Result: complete failure and disintegration. That's something even airliners aren't built for.

Counterpoint: if Falcon 9 or the Atlas V N22 violently turn to the side and snap in half, Dragon 2 and Starliner (respectively) both escape successfully with no LOC.

15 hours ago, Wjolcz said:

OK, now I remembered Antares. The second stage seemed fine for the most part, so maybe SS could ditch all the heavy fuel and then use SL Raptors and fuel from the header tanks as LES? That would probably take too much time to do though.

Dumping the fuel would take too long.

15 hours ago, Ultimate Steve said:

On Starship LES, there is plenty of room between the raptor bells for emergency single use solid rocket boosters or also more raptors.

They would never put SRBs on there, but they might very well do six SL raptors instead of three. I could see multiple configurations based on use case:

The tanker has no cargo so it doesn't need any 0/0 abort and can have a TWR less than 1 at sea level. The cargo starship at least needs a fighting chance and so it has an additional SL engine to allow it to slowly pull away. The cargo version would also be uniquely suited for massive deliveries to the lunar surface given its better hover capability on a single engine in low lunar gravity. The crew version not only has the heritage of the tripod engine configuration from the tanker (as well as Mk1/2 for that matter), giving it the highest data availability and proven reliability, but it would have three fixed, simplified SL engines that cannot throttle but are uprated to 2.45 MN. They would fire for only a few moments at nominal staging to really give Starship a spry jump away from Superheavy, allowing SL-engine shutdown to occur sooner and take more advantage of those vacuum engines for the rest of the ascent, and would give vital thrust in a 0/0 abort.

[kerbiloid]

1 hour ago, Wjolcz said:

Got to LEO with Vostok and Mercury. Any stations there?

Any stations bigger than Scott's and Amundsen's in orbit?

1 hour ago, Wjolcz said:

If you want bigger things in space you need to use bigger rockets.

If you want to carry 40 people, you need 40 horses 4 carriages 1 bus.
If to deliver 1 000 t of fuel to the Moon you have to spend 1 000 000 t of cheap fuel in the Earth atmosphere, and refine 10 000 000 t of minerals, chemicals, and water, it's not just "bigger rockets", it's a "suicidal burn".

To have mass traffic you need at least similar fuel-to-total mass ratio like you have on the Earth.

1 hour ago, Wjolcz said:

I really don't get this one. Guess I'm not smart enough. Starship is not a sailship, neither was Saturn V.

Sailships were nice. For seas.
Chemical engines are nice. For ballistic missiles.

***

Let's have a look.

Moon = 400 000 km far.
Mars = 0.5 .. 2.5 AU far = 100..300 mln km.
Belt = 3 AU ~= 450 mln km.
Jupiter = 5 AU ~= 800 mln km.
Jup's moonz: at least 3 km/s per every interorbital maneuver, so ~10 km/s to visit any from far Jovian orbit.
Saturn&Titan = 9.6 AU ~= 1 500 mln km
Pluto = 40 AU ~= 6 000 mln km

***

We know, the artificial gravity is extremely expensive.
It requires a centrifuge of ~100 m radius, overcomplicates the ship, and makes it dynamically unstable.
It requires a lot of power, so a big reactor.
It forces to populate the centrifuge with tens, maybe hundreds of people.
We don't like artificial gravity. It may be nice for stations but unlikely for ships.
A zero-G ship is many times simpler, cheaper, reliabler, manufacturabler, usabler.
Whenever you can, make a zero-G ship.

We know that a human can spend in zero-G about 1.5 years and restore. We are sure he can even survive for 3 years (a Martian expedition with no landing). But that's the limit.
So, it's wise to limit any expedition with Martian values: 6..8 months to there, same to here, 1.5 years at the place.

As well, every month spent by a specialist in flight is minus one month of his usage in production.
So, 6 months is an absolute upper limit. No six months - no bucks, no roger!'s.

***

So, a reasonable zero-G trip duration to one end is 6..8 months ~= 20 mln s.

Pluto = 6 000 mln km / 20 mln s  = 300 km/s.
Saturn = 1 500 mln km / 20 mln s = 75 km/s
Jupiter = 800 mln km/s/ 20 mln s = 40 km/s
Belt = 450 mln km/s/ 20 mln s = 20 km/s
Mars = 100..300 mln km/s/ 20 mln s = 5..15 km/s, but thanks to ballistics, the value can be lower.

Obviously, we can't get farther than Mars on chemicals.

***

For the Belt usage without artificial gravity and years-long trips we need total delta-V = 4 * 20 km/s + something ~= 100 km/s.

Having 100 km/s onboard, we can (if have enough TWR) lift spending about 50 km/s.
This means about 5 000 s of 1 g. So, we can get to 100 km height at 20 m/s, a car speed.
So, if lift at 100 m/s (a plane speed), we can reach the orbital altitude in 1000 s  = 20 min with no heating, no significant drag, in a usual airship cabin. Then slowly get down.
And spend just ~=(1000 * 10 + 8000) * 2 ~= 40 km/s.
(Then who needs that space lift and reusable chemical rockets.)

***
For Titan/Saturn/Jupiter we need ~= 75*4 + something ~= 350 km/s. Or ~= 150..200 km/s if refuel there.

Having 200 km/s onboard, we can get to the Mars, refuel, and get back in ~= 2..6 weeks, about a month.
A month-long flight is much more liberal to the ship, its reliability, comfort, volume, backup options, biomedical countermeasures, human physical and mental health.

Having 200 km/s onboard but without refuel we can get to the Moon in 400 000 / 50 = 8 000 s, i.e. 2+ hours, like a plane flies between cities.

***

Having 300 * 4 = 1 200 km/s onboard, we can visit Pluto (without refuel).
So, then we can get to Mars with refuel in 100..300 / 600 * 1 000 000 / 86 400 = 2..6 days.
I.e. no zero-G-related  equipment except hygiene bags and candies is required at all. A bag of rations, a cooler of water. No radiation exposure.

Moon trip takes 400 000 / 300 ~= 20 min. Overpowered, not required.

***

So.
When we get 100 km/s onboard, we can start using Mars and Belt. Regular air ships get to LEO when needed, no "launches" happen anymore.
When we get 200 km/s onboard, we can start using Jupiter and Saturn. Mars and Belt get usual.
When we get 1 200 km/s onboard we can study all major bodies in Solar Systems, fly to Mars in Cessna cabin reinforced with duct tape, having a lunchbox and a can of water.

***

This makes unhandy having 90% of ship volume occupied by tanks,
Say, the propellant should take not 20% of the ship mass.

ISP*g / delta-V = 1/ ln(1.2) ~= 5.5

ISP*g is, respectively: 550 km/s, 1 100 km/s, 6 600 km/s.
Obviously this is about only fusion drives.

***

Summary.
When gas-core fission reactors appear, we can send cargo and uncrewed crafts, and have occasional recon trips to Mars, Belt, and sometimes beyond.
When fusion engines will reach ISP*g = 500 km/s (or ISP = 50 000 s), the life will begin, the human expansion will can has a start.

Until that, all those methane-schmethane are just for Martian Apollo missions and their lunar cosplay.

***

In turn the fusion drives must be compact, so absolutely aneutronic, with magnetic nozzles and no fuel cryotanks.
So, when the first penta¹¹borane fusion reactor first time ignites, the real space epoch will begin, with "multiplanetary", "colonization", etc.

Until that we keep playing KSP and enjoying animations and occasional Starships.

***

(corrected several typos)

Edited October 1, 2019 by kerbiloid

[sevenperforce]

Some of the most beautiful (non-official) renders I've seen so far.

Full posting:

https://www.humanmars.net/2019/10/renders-of-spacex-new-starship-design.html

Edited October 1, 2019 by sevenperforce

[tater]

 

[Geonovast]

It's about time he got a 1 on 1 with Elon. 

[tater]

From the video (a lot of wasted talk on aerospikes): In the test vehicles, Tesla motors run hydraulic accumulators to drive the flaps. In future, they want direct electric actuators. The current header tanks are in the nose like cargo, in future they were be integral to the nose structure.

[sevenperforce]

10 minutes ago, tater said:

 

YESSSS I just watched it on high speed and came here to post it!!!

This was spectacular.

A few takeaways:

• Despite all the renders we saw, they WILL put header tanks in the nose permanently, and make them monocoque tanks with smaller nested bulkheads rather than suspended as in Mk1/2.
• Elon is a nerd. A HUGE nerd. He is also ridiculously smart. I doubt there are many science/engineering subjects where I know anything he doesn't know, other than the obvious stuff like earth science. Maybe a few edge cases, but not many.
• Elon has discussed aerospikes at SpaceX internally many times. He would happily develop them if he could find an area where they would be the best choice. He doesn't like them because they have poor combustion efficiency and aren't needed when you can optimize engines independently for SL and vacuum.
• Starship is using Tesla batteries and Model 3 motors. Mk1 and Mk2 are using the motors to drive a hydraulic reservoir for fin actuation, but starting with Mk3 they will go to direct-electric drive for reduced mass and simplicity.
• Elon talked about how school trains you to answer the professor's question rather than asking if it is the right question. Referenced HGTTG. Talked about how much efficiency is lost between departments because they are trying to optimize for the solution the other department gave them rather than synergizing.

AND SO MUCH MORE

[tater]

He's better 1 on 1 than the large crowd events.

[Wjolcz]

3 minutes ago, sevenperforce said:

Starship is using Tesla batteries and Model 3 motors. Mk1 and Mk2 are using the motors to drive a hydraulic reservoir for fin actuation, but starting with Mk3 they will go to direct-electric drive for reduced mass and simplicity.

This is interesting. I thought it would be the other way around. Thought electric first would be easier to do.

[sevenperforce]

Just now, Wjolcz said:

This is interesting. I thought it would be the other way around. Thought electric first would be easier to do.

My sense is that large-component actuation with hydraulics has so many clean COTS solutions that it was easier to just build it that way, and iterate to get direct-drive electric.

Just now, tater said:

He's better 1 on 1 than the large crowd events.

I know! I feel like I could sit with good beer and talk to him for hours.

7 minutes ago, tater said:

From the video (a lot of wasted talk on aerospikes)...

Blasphemy!

Seriously I loved hearing Elon talk about aerospikes just for the insight into his brain.

[tater]

 

[magnemoe]

59 minutes ago, kerbiloid said:

Any stations bigger than Scott's and Amundsen's in orbit?

If you want to carry 40 people, you need 40 horses 4 carriages 1 bus.
If to deliver 1 000 t of fuel to the Moon you have to spend 1 000 000 t of cheap fuel in the Earth atmosphere, and refine 10 000 000 t of minerals, chemicals, and water, it's not just "bigger rockets", it's a "suicidal burn".

To have mass traffic you need at least similar fuel-to-total mass ratio like you have on the Earth.

Sailships were nice. For seas.
Chemical engines are nice. For ballistic missiles.

***

Let's have a look.

Moon = 400 000 km far.
Mars = 0.5 .. 2.5 AU far = 100..300 mln km.
Belt = 3 AU ~= 450 mln km.
Jupiter = 5 AU ~= 800 mln km.
Jup's moonz: at least 3 km/s per every interorbital maneuver, so ~10 km/s to visit any from far Jovian orbit.
Saturn&Titan = 9.6 AU ~= 1 500 mln km
Pluto = 40 AU ~= 6 000 mln km

***

We know, the artificial gravity is extremely expensive.
It requires a centrifuge of ~100 m radius, overcomplicates the ship, and makes it dynamically unstable.
It requires a lot of power, so a big reactor.
It forces to populate the centrifuge with tens, maybe hundreds of people.
We don't like artificial gravity. It may be nice for stations but unlikely for ships.
A zero-G ship is many times simpler, cheaper, reliabler, manufacturabler, usabler.
Whenever you can, make a zero-G ship.

We know that a human can spend in zero-G about 1.5 years and restore. We are sure he can even survive for 3 years (a Martian expedition with no landing). But that's the limit.
So, it's wise to limit any expedition with Martian values: 6..8 months to there, same to here, 1.5 years at the place.

As well, every month spent by a specialist in flight is minus one month of his usage in production.
So, 6 months is an absolute upper limit. No six months - no bucks, no roger!'s.

***

So, a reasonable zero-G trip duration to one end is 6..8 months ~= 20 mln s.

Pluto = 6 000 mln km / 20 mln s  = 300 km/s.
Saturn = 1 500 mln km / 20 mln s = 75 km/s
Jupiter = 800 mln km/s/ 20 mln s = 40 km/s
Belt = 450 mln km/s/ 20 mln s = 20 km/s
Mars = 100..300 mln km/s/ 20 mln s = 5..15 km/s, but thanks to ballistics, the value can be lower.

Obviously, we can't get farther than Mars on chemicals.

***

For the Belt usage without artificial gravity and years-long trips we need total delta-V = 4 * 20 km/s + something ~= 100 km/s.

Having 100 km/s onboard, we can (if have enough TWR) lift spending about 50 km/s.
This means about 5 000 s of 1 g. So, we can get to 100 km height at 20 m/s, a car speed.
So, if lift at 100 m/s (a plane speed), we can reach the orbital altitude in 1000 s  = 20 min with no heating, no significant drag, in a usual airship cabin. Then slowly get down.
And spend just ~=(1000 * 10 + 8000) * 2 ~= 40 km/s.
(Then who needs that space lift and reusable chemical rockets.)

***
For Titan/Saturn/Jupiter we need ~= 75*4 + something ~= 350 km/s. Or ~= 150..200 km/s if refuel there.

Having 200 km/s onboard, we can get to the Mars, refuel, and get back in ~= 2..6 weeks, about a month.
A month-long flight is much more liberal to the ship, its reliability, comfort, volume, backup options, biomedical countermeasures, human physical and mental health.

Having 200 km/s onboard but without refuel we can get to the Moon in 400 000 / 50 = 8 000 s, i.e. 2+ hours, like a plane flies between cities.

***

Having 300 * 4 = 1 200 km/s onboard, we can visit Pluto (without refuel).
So, then we can get to Mars with refuel in 100..300 / 600 * 1 000 000 / 86 400 = 2..6 days.
I.e. no zero-G-related  equipment except hygiene bags and candies is required at all. A bag of rations, a cooler of water. No radiation exposure.

Moon trip takes 400 000 / 300 ~= 20 min. Overpowered, not required.

***

So.
When we get 100 km/s onboard, we can start using Mars and Belt. Regular air ships get to LEO when needed, no "launches" happen anymore.
When we get 200 km/s onboard, we can start using Jupiter and Saturn. Mars and Belt get usual.
When we get 1 200 km/s onboard we can study all major bodies in Solar Systems, fly to Mars in Cessna cabin reinforced with duct tape, having a lunchbox and a can of water.

***

This makes unhandy having 90% of ship volume occupied by tanks,
Say, the propellant should take not 20% of the ship mass.

ISP*g / delta-V = 1/ ln(1.2) ~= 5.5

ISP*g is, respectively: 550 km/s, 1 100 km/s, 6 600 km/s.
Obviously this is about only fusion drives.

***

Summary.
When gas-core fission reactors appear, we can send cargo and uncrewed crafts, and have occasional recon trips to Mars, Belt, and sometimes beyond.
When fusion engines will reach ISP*g = 500 km/s (or ISP = 50 000 s), the life will begin, the human expansion will can has a start.

Until that, all those methane-schmethane are just for Martian Apollo missions and their lunar cosplay.

***

In turn the fusion drives must be compact, so absolutely aneutronic, with magnetic nozzles and no fuel cryotanks.
So, when the first penta¹¹borane fusion reactor first time ignites, the real space epoch will begin, with "multiplanetary", "colonization", etc.

Until that we keep playing KSP and enjoying animations and occasional Starships.

***

(corrected several typos)

You can make artificial gravity by linking up two starships or similar with an wire and spin this up. 
None is working seriously on gas core fission, fusion is more realistic. 

I agree that starship is not perfect for deep space. its an orbital rocket after all.
And yes going to the belt with it is probably out, near earth asteroids will be on the table. Again spin is an option, for other types of ships its probably easier. 
This is manned mind you, starship enables some insane robotic missions with an 3rd stage who is filled in orbit. 
Mind you that something like starship is pretty much required to build the huge interplanetary ships. 

[tater]

Just now, sevenperforce said:

Seriously I loved hearing Elon talk about aerospikes just for the insight into his brain.

It would have been great for a long form interview, absolutely. Like a Joe Rogan sort of thing, but with someone who can actually ask the right questions.

Given the limited time frame, I saw it as a lost opportunity, I guess. The new info we got (hydraulics, electric motors in future, and integral header tanks) was literally in the last few seconds, a fraction of the time on aerospikes.

I think that SpaceX is open enough to data that they will eventually end up with pure space vehicles, and Earth<---->LEO vehicles.

Take a variant Starship. Remove all TPS. Remove fins. Jettison the entire fairing. You have a cylinder in space now that still has attitude control, solar power, and can be refilled with other Starships. You have a tug/ferry very much in the spirit of the original NASA STS concept (before shuttle stole the name of what was meant to be a SYSTEM of multiple vehicles). What's the dry mass of Starship minus all that stuff? 75 tons? Less?

[kerbiloid]

15 minutes ago, magnemoe said:

You can make artificial gravity by linking up two starships or similar with an wire and spin this up. 

1. Just replace one set of dynamical stability problems with another one.
2. Anyway doesn't solve the problem of a specialist flying instead of working. You keep paying him salary while he keeps loosing his skills and not working.
If he spent 10 years in flights, unlikely he can be a good specialist on ground. And if grow an engineer for a single trip, when can he get skilled.
3. The longer is the flight - the greater is total dose.
4. The longer is the flight - the more supplies is required.
5. The longer is the flight - the more probable is critical malfuction. More backups, more redundancy, more complexity, more fuel to spend.
6. Health. Humans get ill from time to time, and one thing to have a week trip, another one to have a year-long journey.

So, the artificial gravity is nice for stations, but not for space buses.

15 minutes ago, magnemoe said:

None is working seriously on gas core fission, fusion is more realistic. 

Even hadn't a doubt, but tried to be objective.

15 minutes ago, magnemoe said:

Mind you that something like starship is pretty much required to build the huge interplanetary ships. 

I would presume that something like this

Spoiler

matches the huge interplanetary ship requirement much closer than Starship.

Edited October 1, 2019 by kerbiloid

[magnemoe]

23 minutes ago, sevenperforce said:

YESSSS I just watched it on high speed and came here to post it!!!

This was spectacular.

A few takeaways:

• Despite all the renders we saw, they WILL put header tanks in the nose permanently, and make them monocoque tanks with smaller nested bulkheads rather than suspended as in Mk1/2.
• Elon is a nerd. A HUGE nerd. He is also ridiculously smart. I doubt there are many science/engineering subjects where I know anything he doesn't know, other than the obvious stuff like earth science. Maybe a few edge cases, but not many.
• Elon has discussed aerospikes at SpaceX internally many times. He would happily develop them if he could find an area where they would be the best choice. He doesn't like them because they have poor combustion efficiency and aren't needed when you can optimize engines independently for SL and vacuum.
• Starship is using Tesla batteries and Model 3 motors. Mk1 and Mk2 are using the motors to drive a hydraulic reservoir for fin actuation, but starting with Mk3 they will go to direct-electric drive for reduced mass and simplicity.
• Elon talked about how school trains you to answer the professor's question rather than asking if it is the right question. Referenced HGTTG. Talked about how much efficiency is lost between departments because they are trying to optimize for the solution the other department gave them rather than synergizing.

AND SO MUCH MORE

They will need to insulate the tanks for deep space missions, this is not needed for say an tanker version still an cone shaped tank setup makes sense. 
Having the header tanks in the top give us an obvious abort mode if we put the crew right below the tanks. 

[sevenperforce]

18 minutes ago, magnemoe said:

This is manned mind you, starship enables some insane robotic missions with an 3rd stage who is filled in orbit.

Or even filled on the pad. You could stack two five-meter DCSSes together with a single RL-10 and loft it into orbit easily, with up to 40 tonnes of terminal payload. Using excess props for a Starship elliptical kick burn before payload separation, you get the following performance:

1. 40 tonnes: 3449 m/s
2. 30 tonnes: 4280 m/s
3. 15 tonnes: 6170 m/s
4. 10 tonnes: 7176 m/s
5. 4 tonnes: 8962 m/s

And that is with a SINGLE launch priced at under $20M. (Elon says $2-10M but I am sandbagging.) Imagine what you could do with a 30-tonne spacecraft headed to the asteroid belt, or ten tonnes on a two-year transit to Jupiter, or a 4-tonne lander on freaking Triton.

18 minutes ago, magnemoe said:

Mind you that something like starship is pretty much required to build the huge interplanetary ships. 

Indeed. It's all very well and good to pine for a 50-tonne gas-core thermal nuke for interplanetary missions, but you have to get into into space. Are you going to wait for SLS?

55 minutes ago, tater said:

It would have been great for a long form interview, absolutely. Like a Joe Rogan sort of thing, but with someone who can actually ask the right questions.

Given the limited time frame, I saw it as a lost opportunity, I guess. The new info we got (hydraulics, electric motors in future, and integral header tanks) was literally in the last few seconds, a fraction of the time on aerospikes.

There are a few questions still out there but I get the sense that most unanswered questions are still under dev at this point.

Have we ever received any indication of the propellant load for the header tanks? I wouldn't assume Mk1 and Mk2 have the full header tanks, just because we don't know, but it could be. I would love to see some more detailed renders that account for having monocoque tanks in the nose and how the payload space will adapt. In that video, Elon called the interior of the fairing the "cargo bay" so it may be moving in that direction (again, despite those renders). 

55 minutes ago, tater said:

I think that SpaceX is open enough to data that they will eventually end up with pure space vehicles, and Earth<---->LEO vehicles.

Take a variant Starship. Remove all TPS. Remove fins. Jettison the entire fairing. You have a cylinder in space now that still has attitude control, solar power, and can be refilled with other Starships. You have a tug/ferry very much in the spirit of the original NASA STS concept (before shuttle stole the name of what was meant to be a SYSTEM of multiple vehicles). What's the dry mass of Starship minus all that stuff? 75 tons? Less?

Probably 75-85 tonnes, yeah. But that would only work for ferrying outward, not returning. It's a problem with a LOT of possible solutions.

46 minutes ago, magnemoe said:

Having the header tanks in the top give us an obvious abort mode if we put the crew right below the tanks. 

Not without LF engines.

[RealKerbal3x]

10 minutes ago, sevenperforce said:

In that video, Elon called the interior of the fairing the "cargo bay" so it may be moving in that direction (again, despite those renders). 

A cargo bay doesn't have to be inline. The forward-opening clamshell design of the payload fairing shown on the SpaceX website is still a cargo bay.

[tater]

9 minutes ago, sevenperforce said:

Probably 75-85 tonnes, yeah. But that would only work for ferrying outward, not returning. It's a problem with a LOT of possible solutions.

Such a tug has ~10,500 m/s dv empty.

With 100 tons cargo it's 7400 m/s. Going someplace like EML-2 is ~3500m/s, so that tug with 100t can drop that 100t at EML-1, then have a lot or dv left (as it's now much lighter). It can absolutely come back to Earth, and propulsively brake in LEO, then get retanked, and do it again.

[magnemoe]

1 hour ago, RealKerbal3x said:

A cargo bay doesn't have to be inline. The forward-opening clamshell design of the payload fairing shown on the SpaceX website is still a cargo bay.

Still think an shuttle type double door or an single side hinged one is better, for one its enables unloading then landing. Also makes cargo integration much easier. 

[ThatGuyWithALongUsername]

1 hour ago, tater said:

I think that SpaceX is open enough to data that they will eventually end up with pure space vehicles, and Earth<---->LEO vehicles.

Take a variant Starship. Remove all TPS. Remove fins. Jettison the entire fairing. You have a cylinder in space now that still has attitude control, solar power, and can be refilled with other Starships. You have a tug/ferry very much in the spirit of the original NASA STS concept (before shuttle stole the name of what was meant to be a SYSTEM of multiple vehicles). What's the dry mass of Starship minus all that stuff? 75 tons? Less?

Ooh, you gave me an idea, how about this:

Take a CREW variant and make the same modifications. Launch it into orbit. Hey, you can even go a bit past LEO with some tankers. Then send up crew, drain the tanks, and make the whole thing a giant "wet lab" space station. Plenty of room for long-term experiments.