News Elon Musk wants to put millions of people on Mars.

[Urwumpe]

And how much would be the delta-v using the 382 s vacuum Isp for the booster? :thumbup:

BTW, this collection of slides from Elon's presentation was posted to Reddit:

http://imgur.com/a/20nku

Bob Clark

Its not 382 s - remember the effect of a vacuum optimized noozle vs a sea-level optimized nozzle. The presentation slide talks about different nozzles there and only state the dominant ISP value:

The earlier stated value of 363 s for vacuum performance of the Raptor engine with sea-level nozzle is more realistic there.

I get 8109 m/s then.

If you assume sea-level specific impulse, 500 tons of payload and 7% propellant for return, you get a total impulse of 6075 m/s by the booster.

A quick calculation with Excel looks like that:

With return propellant in the booster reserved, the MCT should be able to haul 50 tons of payload into LEO (300 tons of fuel in the lander on launch).

That is enough for sustaining a relative large crew over a longer period of time. Assuming very minimalistic crew accommodation (85 kg mass per colonist, 8 kg per day food+water+oxygen per colonist, 150 days of transit), this results in a maximum crew of 38 colonists.

Such a large crew would make a really interesting Orbiter project... like Orbiter meets Mars Simulation Project. :lol:

---------- Post added at 02:03 PM ---------- Previous post was at 12:02 PM ----------

Another calculation: With full propellant tanks in the MCT lander and 400 tons of cargo, it is possible to reach LEO with a tiny bit of fuel remaining in the MCT Lander. MTOW is then 9475 tons or about five space shuttles. The MCT Lander would be burning for 222 seconds at full thrust in that scenario. The MCT Booster would have a burn time of 151 seconds without throttling. (Take-off acceleration: 13.5 m/s .... low and slow, with such a large rocket, it would appear to take ages to lift off, about 9 seconds to clear the tower)

 

[RGClark]

The earlier stated value of 363 s for vacuum performance of the Raptor engine with sea-level nozzle is more realistic there.

I get 8109 m/s then.

If you assume sea-level specific impulse, 500 tons of payload and 7% propellant for return, you get a total impulse of 6075 m/s by the booster.
...

How are you calculating the delta-v for the bare stage (no payload) case? Even with a 363 s Isp, I get an "ideal delta-v", which is the delta-v without gravity and air drag losses, of over 11,000 m/s:

363*9.81ln(1 + 6700/275) = 11,500 m/s.

Using the ideal delta-v number, the required delta-v to orbit is in the range of 30,000 ft/s, about 9,100 m/s; so this value is well above that. That translates into significant payload to orbit if you only require a delta-V of 9,100 m/s.

Modern Engineering for Design of Liquid-Propellant Rocket Engines, p.12

Bob Clark

 

[Urwumpe]

Of course with the second stage as payload of the first. Everything else would be misleading. I just calculated initially with a minimalist second stage - not more mass than 500 tons mass, instead of the 2500 tons of a fully loaded second stage. Call it arbitrary, but launching with only one fifth of the reference payload is at least observed in reality, which means it can be done.

 

[N_Molson]

That SpaceX mass hysteria phenomenon is really beyond my understanding...

 

[Urwumpe]

That SpaceX mass hysteria phenomenon is really beyond my understanding...

Well, as if ESA does the same for PR (What a tiny bit of effort can be worth: See Rosetta).

Also SpaceX now has a 3500 MN cryogenic Full-Flow Staged Combustion Engine ... what does Safran Aircraft Engines have?

 

[Col_Klonk]

http://imgur.com/a/20nku

I'd like to see that thing get up into orbit in one piece !!

Why doesn't he just build the rocket, in orbit, out of 2 or 3 smaller modules ?

 

[Urwumpe]

I'd like to see that thing get up into orbit in one piece !!

Why doesn't he just build the rocket, in orbit, out of 2 or 3 smaller modules ?

Well, maybe because he wants it that way. :lol:

It looks like the system should be fully reusable, so an assembly in orbit would make this tough. And a Mars cycler is not easier.

 

[N_Molson]

I'm not an ESA-believer (they lost me not turning the Ariane 5 and the HTV to a CTV, plus those foolish downgraded Ariane 6 plans), but SpaceX stuff is still as much vaporware as Roscosmos, China or the other USA space plans. Also I still don't see how dividing the economic power of a nation between a dozen of sub-agencies is going to solve any problem, beyond skyrocketing communication budgets to make cool anims, top-quality PowerPoint(TM) dias and prophetic (very optimistic is not strong enough) speeches.

SpaceX is re-developing engines that already exist. An enormous amount of time and money could have been saved securing the production lines of proven high-end components such as the Atlas-V or Delta-IV hardware. Or even make the R-7 which is cheap and has a near-perfect record an International Crew Launch Vehicule built under license in several countries. You probably could send up to 9 tons in LEO from the Cape.

 

[Urwumpe]

SpaceX is re-developing engines that already exist.

Name one cryogenic full-flow staged combustion engine in existence before the Raptor. Only one is enough. :tiphat:

The Russians had the RD-270, which was pretty much full-flow, but based on storable propellants and it was cancelled during testing.

https://en.wikipedia.org/wiki/RD-270

 

[jroly]

I watched the presentation and was impressed by it, I felt embarrassed at the end for Musk with the number of stupid questions and there were two separate questions where the person used the S*** word, what is wrong with these people?

 

[Urwumpe]

I watched the presentation and was impressed by it, I felt embarrassed at the end for Musk with the number of stupid questions and there were two separate questions where the person used the S*** word, what is wrong with these people?

I have no idea. Usually you would expect somebody at a spaceflight conference say something like "Worst Mars colonization plan ever!"

 

[orb]

The most important questions asked :

 

[Urwumpe]

The most important questions asked :
Watch Elon Musk tackle bizarre audience questions - YouTube

Honestly, would I have been standing on that stage, it would have been impossible for me to not collapse laughing at a point. :rofl:

 

[fred18]

http://imgur.com/a/20nku

I don't know if anybody already stated it, but the slides seem like a guide to addon developing :lol: with those numbers it shouldn't be too hard to build an addon about this

 

[Thunder Chicken]

Elon Musk wants to name at least one of the ships Heart of Gold.

https://www.inverse.com/article/21482-spacex-mars-ship-name

42 Raptor engines on the booster. Coincidence? That would be interesting if the size of the Raptor was not determined by stability in the combustion chamber or some other engineering limitation, but because it had to provide 1/42nd of the total necessary thrust, because Elon Musk said so. That would be some mad scientist thinking right there.

 

[Hlynkacg]

That's some first rate placebomany right there.

 

[Pipcard]

That would be interesting if the size of the Raptor was not determined by stability in the combustion chamber or some other engineering limitation, but because it had to provide 1/42nd of the total necessary thrust, because Elon Musk said so. That would be some mad scientist thinking right there.

It's great, because it means that my fictional rocket after M-III can have 39 engines.

 

[boogabooga]

Elon Musk wants to name at least one of the ships Heart of Gold.

https://www.inverse.com/article/21482-spacex-mars-ship-name

42 Raptor engines on the booster. Coincidence? That would be interesting if the size of the Raptor was not determined by stability in the combustion chamber or some other engineering limitation, but because it had to provide 1/42nd of the total necessary thrust, because Elon Musk said so. That would be some mad scientist thinking right there.

So, the N1 route of many small engines?

 

[Thunder Chicken]

So, the N1 route of many small engines?

Well, each Raptor is 700,000 lbs thrust apiece, so really a lot of big engines for a very big rocket.

 

[boogabooga]

Well, each Raptor is 700,000 lbs thrust apiece, so really a lot of big engines for a very big rocket.

But each is "small" (2.3%) compared to total thrust.

Elon Musk wants to name at least one of the ships Heart of Gold.

https://www.inverse.com/article/21482-spacex-mars-ship-name

42 Raptor engines on the booster. Coincidence? That would be interesting if the size of the Raptor was not determined by stability in the combustion chamber or some other engineering limitation, but because it had to provide 1/42nd of the total necessary thrust, because Elon Musk said so. That would be some mad scientist thinking right there.

It took me a while to realize "42" is a Douglas Adams thing. I'm not really a fan.

But, my guess is they knew that it would be several dozen engines, and then went with 42 specifically.