totm nov 2023 SpaceX Discussion Thread

[tater]

Or Ithacus:

Call the orbital one Pegasus.

Or name it after Phil Bono.

 

[NSEP]

Lets all hope the BFR becomes a Big Fuctional Rocket and not a Big Floppy Rocket.

[TheEpicSquared]

3 minutes ago, NSEP said:

Lets all hope the BFR becomes a Big Fuctional Rocket and not a Big Floppy Rocket.

Or a Big Fictional Rocket. Hopefully it becomes a Brilliantly Fantastic Rocket instead.

Edited September 29, 2017 by TheEpicSquared

[wumpus]

2 minutes ago, TheEpicSquared said:

Or Big Fictional Rocket

In that case we want Big Funded Rocket

[Nibb31]

16 minutes ago, tater said:

Or Ithacus:

Call the orbital one Pegasus.

Or name it after Phil Bono.

 

Not the name of a bird of prey (Kestrel, Merlin, Falcon, etc...) or a dragon (Dragon, Draco...). Try again.

Edited September 29, 2017 by Nibb31

[Nefrums]

20 minutes ago, TheEpicSquared said:

SpaceX should have a naming competition. Winner gets a free tour of the HQ or something.  

"Rocky McRocketface"

[kerbiloid]

It should be an animal. They always name after animals: Grasshopper, Dragon, Draco, SuperDraco, Raptor.
So, no Ithacus.
Maybe, http://hitchhikers.wikia.com/wiki/Magrathean_sperm_whale.
Or just Moby-Dick.

[cubinator]

The targeted window is in 2024, and I should graduate from college in 2022. I can make it! Of course, in traditional SpaceX fashion, it's quite likely there will be delays, leaving me plenty of time to be ready for the trip.

[kerbiloid]

Spoiler

4 minutes ago, cubinator said:

The targeted window is in 2024, and I should graduate from college in 2022. I can make it! Of course, in traditional SpaceX fashion, it's quite likely there will be delays, leaving me plenty of time to be ready for the trip.

Imho, you have enough time to get Ph.D.

 

[RedKraken]

11 hours ago, sevenperforce said:

. Swap out the four Vac raptors for SL ones and you could do the suborbital hop with the Spaceship alone. 

Sev, I tried modelling this in RO a while back.

I could not make it work with the BFS dry mass fractions and the methane sea-level engines (334-361s).

I always came up short. No payloads.

iirc KSC to London requires a bit over 9100m/s. (***Checked with modified F9 --> 8700m/s.... Apologies!).

Almost low orbit numbers. Apogee ~160km.

This BFS design packs maybe 8900 m/s with all sea-level engines.

You might be able to get the craft city to city, but you will carrying featherweight cargo.

(It might work for lightweight mail.)

I think this is why they have to use the boosters.

Methane appears to fall just short (maybe 20 seconds of specific impulse) for useful single stage operations on planet earth.

Edited September 29, 2017 by RedKraken
delta V check in RO

[cubinator]

7 minutes ago, kerbiloid said:

  Hide contents

Imho, you have enough time to get Ph.D.

 

I will make clear to my professors and counselors the urgency of my situation, and hopefully they will be able to help me make it in time. I have been absolutely serious about this since I was five years old, and it's quite exciting to see that I may be less than ten years away from "When I grow up, I want to be an astronaut". I didn't think I wanted to go all the way to Mars at the time, but what the hell. I need to go all out.

[RedKraken]

From titusou @ nsf

[Spaceception]

11 minutes ago, RedKraken said:

From titusou @ nsf

I like the new design better, sleeker and cleaner.

And as for cost, wasn't it in the 10 billion range for the 12 m version? 

Think it's safe to say it'll be somewhere between 5-10 billion.

And yeah, 2024 is aggressive, but humans on Mars before 2030 is definitely possible, especially with the new plans. Course, a lot of things are possible in the next 12ish years, but I'll remain optimistic. 

Edited September 29, 2017 by Spaceception

[Rune]

I just posted this elsewhere, but I think you guys will appreciate the anlaysis better:

So, I have run the numbers on that lunar mission. It's mighty interesting! This could be the real intent behind the whole 'paying for it' thing, finding the customer that foots the bill while feeling like he makes a great deal. Let me explain, and hold on to your hats, 'cause I dunno how long this will be:

First, assumptions. I will assume that the numbers given in the presentation are true (Raptor Isp=375s, empty weight of the orbiter 85mT, max. payload 150mT, max. fuel load 1,100mT/1,250mT in the tanker version because payload is fuel), that the mission is staged from GTO (Geosynchronous transfer orbit, which is reasonable, analysis as to why later), and that the dV map in the wiki is close enough for government work.

Why GTO? Well, according to the wiki, form there it's about 3.2km/s to the lunar surface. Add 2.3km/s to come back to an atmosphere-intercepting Earth orbit, and you get 5,5, well within the 6,4km/s my trusty excel sheet spits out for the BFR orbiter, with full fuel and 150mT in payload. Seems reasonable.

That means that we need a full BFR orbiter at GTO, meaning we first have to refuel it in LEO (at least 8 trips of a tanker if a tanker can transfer 150mT of fuel and suffers little losses). Then, we have to refuel it again form fully-fueled BFR tankers, themselves refueled in LEO, each by its own eight tanker flights. How many tanker flights to GTO we need can increase the total number of launches pretty quickly.

So, how much fuel can a BFR tanker get to GTO, if starting full at LEO? Well, that is easy. Massaging my sheet, I get that a payload of 590mT of fuel makes it to GTO. Coming back is easy, since perigee is still close to the planet, so the tanker can aerobrake. That means you need only slightly more than one tanker (at least!) to refill the ship with payload in GTO after it spends 660mT of fuel getting itself to GTO (again, that excel spreadsheet is neat). Since everything is a rough first-order approximation, let's call it two tanker flights, and the margin will take care of inefficiencies I haven't taken into account.

So all in all, for one to reach the Moon and return, three BFRs must reach GTO, and in turn you have to launch 24 (!) to LEO to get those three up there. Well now, that proposition, at a decent enough launch rate, is starting to sound like a good business market to serve, a single lunar mission a year means two flights each month. There are the high flight rates that could make the whole thing economical, ginormous as it is.

 

Rune. Imagine what that excel spreadsheet is meant for, and why I use it a lot. ^^'

Edited September 29, 2017 by Rune

[sh1pman]

@Rune what if they only refuel the BFR ship just enough to land on the Moon, and ISRU (if it's possible) the fuel required to get back to Earth? Will it decrease the number of launches significantly?

Edited September 29, 2017 by sh1pman

[magnemoe]

16 minutes ago, Rune said:

I just posted this elsewhere, but I think you guys will appreciate the anlaysis better:

So, I have run the numbers on that lunar mission. It's mighty interesting! This could be the real intent behind the whole 'paying for it' thing, finding the customer that foots the bill while feeling like he makes a great deal. Let me explain, and hold on to your hats, 'cause I dunno how long this will be:

First, assumptions. I will assume that the numbers given in the presentation are true (Raptor Isp=375s, empty weight of the orbiter 85mT, max. payload 150mT, max. fuel load 1,100mT/1,250mT in the tanker version because payload is fuel), that the mission is staged from GTO (Geosynchronous transfer orbit, which is reasonable, analysis as to why later), and that the dV map in the wiki is close enough for government work.

Why GTO? Well, according to the wiki, form there it's about 3.2km/s to the lunar surface. Add 2.3km/s to come back to an atmosphere-intercepting Earth orbit, and you get 5,5, well within the 6,4km/s my trusty excel sheet spits out for the BFR orbiter, with full fuel and 150mT in payload. Seems reasonable.

That means that we need a full BFR orbiter at GTO, meaning we first have to refuel it in LEO (at least 8 trips of a tanker if a tanker can transfer 150mT of fuel and suffers little losses). Then, we have to refuel it again form fully-fueled BFR tankers, themselves refueled in LEO, each by its own eight tanker flights. How many tanker flights to GTO we need can increase the total number of launches pretty quickly.

So, how much fuel can a BFR tanker get to GTO, if starting full at LEO? Well, that is easy. Massaging my sheet, I get that a payload of 590mT of fuel makes it to GTO. Coming back is easy, since perigee is still close to the planet, so the tanker can aerobrake. That means you need only slightly more than one tanker (at least!) to refill the ship with payload in GTO after it spends 660mT of fuel getting itself to GTO (again, that excel spreadsheet is neat). Since everything is a rough first-order approximation, let's call it two tanker flights, and the margin will take care of inefficiencies I haven't taken into account.

So all in all, for one to reach the Moon and return, three BFRs must reach GTO, and in turn you have to launch 24 (!) to LEO to get those three up there. Well now, that proposition, at a decent enough launch rate, is starting to sound like a good business market to serve, a single lunar mission a year means two flights each month. There are the high flight rates that could make the whole thing economical, ginormous as it is.

 

Rune. Imagine what that excel spreadsheet is meant for, and why I use it a lot. ^^'

However taking 150 ton to the moon surface only make sense if you set up an permanent base. 
An science mission even one far larger in scope than Apollo would not need 150 ton cargo or an giant lander. 
Now an tourist mission would want an huge lander but would not need so much cargo, 
 

5 minutes ago, sh1pman said:

@Rune what if they only refuel the BFR ship just enough to land on the Moon, and ISRU (if it's possible) the fuel required to get back to Earth? Will it decrease the number of launches significantly?

Moon mission does not include ISRU. We need more moon missions to check how relevant it is. 
Personal favorite is ice inside lava tunnels or cracks. 

[tater]

2 hours ago, Nibb31 said:

Not the name of a bird of prey (Kestrel, Merlin, Falcon, etc...) or a dragon (Dragon, Draco...). Try again.

I was referring to the Phil Bono designs of the 60s that basically aimed to do what BFR hopes to do, Ithacus, and Pegasus.

 

 

 

[regex]

WHAT IS UP WITH ALL THE WINDOWS?

Seriously!

[IncongruousGoat]

1 hour ago, magnemoe said:

Moon mission does not include ISRU. We need more moon missions to check how relevant it is. 
Personal favorite is ice inside lava tunnels or cracks. 

Even if ice is more prevalent than we currently think it is, you're still going to run into problems finding carbon. As far as I know, the moon doesn't have any usable sources, if it has any in the first place.

[tater]

They can do a lunar surface return flight on a full tank, so not needed.

[mikegarrison]

26 minutes ago, IncongruousGoat said:

Even if ice is more prevalent than we currently think it is, you're still going to run into problems finding carbon. As far as I know, the moon doesn't have any usable sources, if it has any in the first place.

The moon originally had basically the same elements that the Earth has. However, I expect that any free carbon near the surface managed to oxidize itself into CO or CO2, and then was blown off by solar radiation. Same for any water vapor, which is why they only expect to find water in ice form, and then only in places where it never gets any solar heating like permanently shadowed craters.

Edited September 29, 2017 by mikegarrison

[magnemoe]

2 minutes ago, mikegarrison said:

The moon originally had basically the same elements that the Earth has. However, I expect that any free carbon near the surface managed to oxidize itself into CO2, and then was blown off by solar radiation. Same for any water vapor, which is why they only expect to find water in ice form, and then only in places where it never gets any solar heating like permanently shadowed craters.

True, also while you can get more water from comets were the water I don't think you get much co2 this way. 
However just oxygen helps, but you would just get it from an permanent base anyway. 

 

19 minutes ago, tater said:

They can do a lunar surface return flight on a full tank, so not needed.

But it need lots of refueling, even topped up twice for the mission, not sure how it would work out with an lighter payload. 

[tater]

Refueling the spacecraft is SOP for all but dropping cargo (maybe with an upper stage) in LEO.

SLS cannot do a moon mission, even a tiny Apollo LEM sized lander, without multiple launches. Orion/EUS, then a cargo launch with a lander, and an upper stage as well. Assume 2 launches at min. 500M$ marginal cost each, plus the 2B$ to run the program. 1-3 B$ depending on how you look at it, all destroyed except part of Orion. If a tanker flight costs a few million to run, then even 5-6 flights is noise compared to 1 SLS flight.

[sh1pman]

15 minutes ago, mikegarrison said:

The moon originally had basically the same elements that the Earth has. However, I expect that any free carbon near the surface managed to oxidize itself into CO or CO2, and then was blown off by solar radiation. Same for any water vapor, which is why they only expect to find water in ice form, and then only in places where it never gets any solar heating like permanently shadowed craters.

Moon surface is actually very reduced, because of all the electrons from the Sun bombarding it non-stop. For example, iron there is in 0 and +2 oxidation states, while on Earth it's pretty much only in the +3 oxidation state.

[kerbiloid]

24 minutes ago, mikegarrison said:

The moon originally had basically the same elements that the Earth has. However, I expect that any free carbon near the surface managed to oxidize itself into CO or CO2, and then was blown off by solar radiation. Same for any water vapor, which is why they only expect to find water in ice form, and then only in places where it never gets any solar heating like permanently shadowed craters.

Also, unlike the Earth, the proto-Moon was completely melted, and any original hydrocarbonates or so have been decomposed into CO2 and H2O, vaporized and dissipated.
So, we should expect even less fluids from the Moon.

Upd.
Also, we should assume that the most demanded good from the Earth will be hydrogen cyanide (HCN).
Because it is carbon and nitrogen.
So, building your Mun base don't forget to put huge tanks for HCN, about a half of your whole base.

Edited September 29, 2017 by kerbiloid