RedKraken

ITS 1950t prop + 150t dry ITS tanker 2500t + 90t dry 6 vac + 3 atmos raptor config 450t to mars 115 day transit on average down to 80 maybe less

first stage 6700t prop on 275t dry 7% propellant for boostback

A 1000 ship fleet .... colonize mars within 100yrs.....ok (slowly backs away)

rcs is methalox too

ITS needs to last 15 missions

3-5 tanker trips

whats the dry mass of that booster ...400t? No 275t

come on Elon u are wasting time...every single person watching knows the why....tell us the how and when!!!! ok...heres the gravy ITS launches dry

where u going sir? "4th rock on the left please"

My jaw is still on the ground. Its a direct mission. 2 stages. 127.8MN is 42(?) atmos raptors at 3MN sl each. 12m diameter. Thats a 10000t rocket. Heh. Booster stages at...2200m/s according to reddit crew. Might actually land back in the launch clamps. Crikey! So many engines. ITS looks like " 9 engines on the MCT ITS - 6 vac/Mars and 3 SL (probably for landing) " from reddit

on a 12m diameter lander (direct mission) : I imagine at least 3 big vac raptors in a triangle with one little atmos raptor in the middle. The atmos is used for the final 1000m (?) of earth landing, with the vacs being buttoned up. Mars landing could be done this way too if u want to protect the vacs. It is a big unit. 85t empty. 100t cargo out (25t back). tank space for 1000t of fuel. Launch barely fueled as 3rd stage on a 6500t bfr. Then 4 or 5 fueling missions. Finally LEO config ~1200t ~7000m/s in tanks. Slightly faster TMI + adjustments cost 4400 m/s. 3 vac raptors produce 900t thrust at 380s. TWR 0.75 6 months transfer Mars EDL start 360t, 2400m/s (125t effective w/ mars gravity) TWR vacs 7.2 ----> this is the big unknown....some estimates of direct mars edl costs are as low as 1800m/s if u need more, lower the cargo tonnage Mars surface 190t, 200 m/s (65t effective). Final Landing twr on atmos engine 3.5 550 days surface mission isru generates 600t fuel Mars surface return config 710t, 7000 m/s (230t effective) TWR is about 3.9 at liftoff. MLO costs 4000 m/s Earth transfer costs 2500 m/s 6 months transfer Earth EDL start 125t, 400 m/s, TWR 2.0 , atmos raptor gives 250t thrust at 320s Earth surface 110t, 100 m/s I have played fast and loose with the numbers here. Ideas and corrections welcome. Agree. Every single item on the timeline would have to work first time. It wont. But I keep my fingers crossed.

Ok we are talking two different mission architectures here.. Directs-to-surface verses the orbital rv. It will be fascinating to find out... not long to go now.... 18hrs

How do you protect those huge fragile 4m bells from mars entry and earth EDL? I can only think of engine dugouts thru the heat shield that have armoured caps like missile silos. You could have your heatshield at the opposite end from your motors....but the flip-around acrobatics and pumping fuel to change COM feels like a bad thing to be doing during EDL.

i'm guessing boiloff over 5-6 month transfer is a big problem for propulsive landing. Embrittlement problems with materials it touches. Hydrogen tanks are massive. i think the fluid management guys have demonstrated ~2% loss per month, but nothing has flown. Centaur upper stage is only good for "a dozen hours". ACES upper due 2020 is supposed to be good for multiple days. Not very encouraging. They may actually take H2 for ISRU on the martian surface. Will cut into payload, but reduces isru complexity and risk. Ice mining+hydrolysis versus 30t of pure H2 ready loaded in the ISRU plant. You get boiloff over the 2yr mission so you take extra to cover. Rob Zubrins RWGS-Eth design gets 30:1 leverage H2 to methalox at very reasonable power (225kW) and weight (1000kg). Makes 1000kg of fuel a day. 600 days surface mission gives you 600t of fuel to get your 110t MCT home. Bob's your uncle. http://www.pioneerastro.com/Team/RZubrin/Mars_In-Situ_Resource_Utilization_Based_on_the_Reverse_Water_Gas_Shift_Experiments_and_Mission_Applications.pdf This awesome paper was from 1997. I dont know what the latest and greatest isru stuff is. ?? I think they are going direct to surface. aerobraking plus propulsive landing. No circ burn at all.

Elon tweeted the vacuum raptor bell is about 14ft (4.2m). 3MN, 380s is a nice surprise. Ive seen suggestions the atmospheric raptor bell would be about 5ft (1.5m)... 2.5MN, 320s reasonable? So Raptor (atmos) 1.5m, 2.5MN, 320s at sea level up to 2.8MN, 360s (sorry lots of guessing here). Raptor (vacuum) 4.2m, 3MN, 380s (all from Elons tweet) SSME is 2.4m, 1.8MN, 366s up to 2.3MN, 452s, 3500kg. F1 was 3.7m, 6.8MN, 263s, 8400kg. M1 hydrolox design was 4.2m, 3.8MN, 310s up to 5.3M 428s , 9000kg. i am very interested in the engine masses.....anyone want to have a guess ???

I can't wait to see this thing fly. 2017 looks like being a very exciting year for rocket-heads. Same

What are your thoughts on this Steve?

Some more issues raised in the NASA forums : 1. Angled engines for landing and take off on Mars : Dont want debris (small rocks and dust) shredding the engines or damaging the ship. The engine dugouts in the heatshield may turn into trenches so the engines can be angled out when required. 2. Vacuum raptors may not be ideal for final touchdown on mars (300% too big ) and will not perform well for an atmospheric earth landing. So we might get a group of smaller (750kN?) dual-purpose (atmos/vac) landing engines at the expense of payload. 3. Refueling in LEO : Mass fraction for two-stage BFR/MCT fueler is horrible. A three-stage vehicle will double your mass fraction and halve your refueling launches. You could recover your second stage on a ballistic trajectory.

Im thinking dry masses of ~150t. Cargo 100t. Total 250t to the surface. Have I made a rookie mistake? Or is it an 85t dry + 15t cargo for total 100t to surface? Back to the VAB RedKraken!

I dont think they will need to refuel at LMO. That 100 tonne payload to surface will shrink to 10(?) for the trip home, frees up lot of dv. They can get home for 7000m/s(?) from mars surface. I agree with your list Nibbs. Cheers!

I dont know how i missed this : https://www.reddit.com/r/spacex/comments/4wks2h/fanmade_mct_and_bfr_architecture_cad_and_math/ Apologies if it has already been posted... i've been away for a while.

I agree...A lot of (really hard) things have to go right. It took five attempts just to land a first stage back on earth under well-known conditions. Heavy EDL is the show-stopper. You can only attempt every two years. Takes 6 months to get the results. You cant pull apart the wreck on a fail. You probably have seen this...Larry Lemke's propulsive landing talk from 2014 : https://www.youtube.com/watch?v=ZoSKHzziLKw

Yep....single core will be truly massive. Interesting times!

The nasa forums are awesome.

I've been playing with BFR/MCT models in realism overhaul. So far i have a 4200t beast : 3-core format with crossfeed. 27 raptors for launch. twr 1.30 at liftoff. The upper stage (MCT) is only partly fueled on launch and must be refueled in LEO before the TMI burn. After the 4000 m/s TMI burn there is about 1800 m/s fuel left for landing on mars. Mars insertion velocity is about 6000 m/s, most of this is wiped off with aerobraking. After all this, i can still only wrangle 75t to the surface. Landing sites are limited to low elevations.