Video: Musk In-depth Discussion
Elon Musk – the Future of Energy & Transport
On November 14 Elon Musk participated in a 90 minute Q&A at the Oxford Martin School with the topic the Future of Energy and Transport. From the abstract, Musk “will talk from his own experiences at the forefront of technology and innovation about what kind of technological transformations are just around the corner and how these can help address the world’s critical challenges.”
http://www.floridatoday.com… Should the next cargo launch to ISS be delayed or not? Is this prudent and wise or just an unnecessary delay to slow commercial space.
Question
Engine twice the size of merlin a instead of merlin 2
Would Spacex be wise to make a rocket engine twice the size of the new merlin engine that will be on the falcon 1.1? wouldn’t flying 4 main engines with a small central merlin for booster return be safer and smarter? would such a configuration still have engine out capablity plus decrease the odds of engine failure
http://www.space.com/18596-… Isn’t this very similiar to the Mars one idea that no one at NASA watch wanted to talk about?
http://nextbigfuture.com/20… COOL no hydro 🙂
depends on the cost and time, if it is cheaper and faster to crank out 8 smaller engines versus 4 larger engines .. stick with 8
Rewrite question since edit doesn’t work at this location
I don’t understand the need for a merlin 2 being as big as Spacex plans to make it.
Wouldn’t it be smarter to make a merlin twice as powerful as the new engine on the falcon 1.1 so that falcon 1.2 could have 4 larger engines with one smaller merlin central engine for booster return.
Wouldn’t this decrease the odds of engine failure and still have engine out capablity??
Wouldn’t this also leave an increamental grow path to a bigger falcon 9 with a larger core that is twice as powerful as the current falcon 9 creating big boosters that could be strapped together like the falcon heavy or a version of Tinkers heavy lifter???
Just seems to me that really big rocket engines and big rocket cores are too expensive to manifacture and handle and maintain.
DTARS:
The new engine will be the methane breathing Raptor. I missed the part about it being twice as powerful as the Merlin but it makes sense. Their next rocket will use these new engines for both stages much like the Falcon 9 does, multiple engines in the first stage, one or two in the second. Elon did say that SpaceX would continue the philosophy of multiple engines in the first stage of future launch vehicles.
Liquid methane is handled in a similar fashion to liquid oxygen so SpaceX has the experience. Methane is a lot cheaper then RP-1 too. The liquid methane tanks would be of a larger volume then for RP-1 so the fuel and oxidizer tanks would be about the same volume. The tradeoffs (hopefully) absorb the extra mass.
So, twice as powerful. Maybe a single core version would be as powerful as a Falcon Heavy, fifty tonnes to orbit. A three core version would be more powerful then a Saturn V… in SLS territory.
If that launch vehicle becomes reusable, (and if it finally works for the Falcon 9, why wouldn’t it) then there’s our railroad over the mountains, clear sailing after that!
Also, piecing things together from all the lectures and interviews, I get the impression Elon Musk is looking at a Mars Direct approach. Launch to Mars transfer orbit, coast, enter Mars atmosphere and land. What flies to Mars, lands on Mars. Maybe they ditch a cruise stage but most of the mass would be lander. SSTO from Mars is a lot easier then Earth (it still hasn’t been done yet) so maybe with on Mars refueling there’s you leg home. Launch from Mars to Earth transfer orbit, coast, reentry and landing or aerobraking into Earth orbit. The latter would be preferable for recycling the spacecraft because being in Earth orbit would mean only a fraction of the energy needs to be expended to go back to Mars a second time (or more). Ahhh… I’m beginning to see the light…
tinker
Yeah, I had the same epiphany the other day: About 6km/s of delta-v (MR ~5 at methane’s ~380s vacuum isp using staged combustion) would get you from earth orbit to mars’ surface, if you have a decent-sized heatshield. If you refuel there, then the same amount of delta-v can put the whole thing back in LEO (or in a reentry path to powered touchdown) with no parts thrown away. And mass ratio 5 and aerobraking is ridiculously easy for a company that makes first stages with 5% empty weight and lunar return rated capsule heatshields.
It sounds more and more like this will be SpaceX’s plan to go to mars reusably and cheaply. It also makes good sense… why didn’t I see any similar concept before?
The only thing else you need is a rocket big enough to put this stage in
LEO fueled, or lift it empty and refuel in orbit. Elon seems to prefer the
“rocket big enough to lift it full” approach. That sounds Saturn-esque, to say the least (working rough numbers, a ~35mT payload, like a trasnhab, takes ~350mT IMLEO, 280mT being fuel).
Ernesto:
Nice to hear that the numbers work too. I was simply using logic based on past projected missions (like Mars Direct) and Elon Musk’s specific and general comments on the subject.
He never talks about orbiting Mars or even visiting it’s moons. He’s going to rely on one motor, the methane fueled Raptor engine, for all systems; first and second stages of launch vehicles, refueled for Mars transfer, landing and refueled to return to Earth.
My guess is that the ‘MCT’ is a combination of the second stage of a Raptor powered launch vehicle and what I call a ‘fairing profile spacecraft structure’ permanently attached above it. I think it would be refueled in orbit because that’s how they would do subsequent missions. It may be able to land on Mars, be refueled and return to Earth but I don’t think they need to be built it to ever land on Earth again. Reusable launch vehicles will make fuel tanker launches economical, especially if the tanker are returned and reused.
The ‘fairing profile spacecraft structure’ could be 22 to 28 feet (7 to 9 meters) in diameter and 60 feet (20 meters) tall. Large enough for four decks of living space and even enough diameter to make a centrifuge large enough so that the crew could at least sleep and shower in Martian gravity during the cruise phase.
All speculation on my part but, as you say, pieces of the puzzle are falling into place.
tinker
Well, I would have also picked up the “launch empty, refuel using smaller launch vehicles launching more frequently” option. Kind of works with a smaller F9R tanker.
But if you read not too much between the lines, it is clear in the video Elon has substantially larger rockets in mind. And it kind of makes some sense in the economics department, “from a certain point of view”.
Let me explain: first, maintenance is never going to be cheaper than on the earth’s surface. I think that is a given. And the fuel has to be launched one way or the other, right? Well, theoretically and disregarding rate of flight issues, the bigger launcher is the more economical. So just land it after every mission (if it can land on Mars, it can land on Earth much easier), inspect, restock, restack, refuel and fly again at the next window.
IF you have a rocket big enough, and cheap enough, the 1/5 vehicle dry mass is a penalty, yes (you have to lift it up every time) but then you have NO orbital operations and can do straight shots. That might save more than 20%.
Is this the right way to look at it? Well, time will tell us, won’t it?
Ernesto,
In the long run, hopefully it will not be an “economics of one mission” decision. If you have multiple missions in the same basic time frame, it may be better having separate ground-to-space and space-to-space vehicles, because your space-to-space vehicles are going to have a much greater payload capacity per unit cost, in terms of both volume and mass, and so multiple ground-to-space launches can be ferried out system by a single space-to-space vehicle, even to multiple destinations. This also makes reuseability easier to develop and more profitable to use.
In the short term, your logic makes sense to me, but in the (not too) long term, I believe we’re much better off thinking in terms of transportation infrastructure rather than single missions. If we think of solar system space as analogous to Earth highways and tractor-trailers, then fuel depots are gas stations and we know where to logically place them; same for maintenance facilities, “motels,” and the rest. If we envision solar system travel in terms of a highway (or a railway, as DTARS suggests), then we have an optimized Earthbound example of all of the facilities and interdependencies which will be most effective and cost effective.
This also allows for multiple “suppliers” to be employed on any single mission, and/or multiple “customers,” and each supplier can develop its own specialty, thereby again making the overall infrastructure more effective.
Steve
as DTARS suggests lolololol
You make me smile sometimes Mr. Steve
IT IS GOING TO HAPPEN!!!!!!
Ernesto:
Assuming a return of Elon’s spacecraft from Mars to Earth orbit, just how hard would aerobraking be? What did you mean when you stated above “mass ratio 5 and aerobraking is ridiculously easy”?
Another way to describe this hypothetical full flight plan to Mars and back would be: USTML/SSTEO (Upper Stage To Mars Landing/Single Stage To Earth Orbit) with subsequent missions being SSTML/SSTEO (Single Stage To Mars Landing/Single Stage To Earth Orbit).
If SpaceX does launch straight to Mars transfer orbit, they really only need to have enough fuel left over for the actual landing so you’re right about them not needing to refuel in orbit first time around. They would be hauling a fair volume of empty tankage to Mars though. Maybe they could outfit those tanks en-route ‘wet lab’ style to acquire more living space.
tinker
Justatinker:
Well, assuming a return to LEO as you say (and remember, as I said, even though it IS the option I would choose, the way I see it, it is not the way SpaceX wants to go), I said mass ratio 5 and aerobraking is ridiculously easy mainly from a empty weight fraction standpoint.
As I am sure you know, the first stage of Falcon 9 is something like 96% fuel, 4% everything else including rockets and interstage. This single stage I talk about, with MR 5, can be just 80% fuel, 20% everything else. Call it the MCT if you want an acronym. 😉
Even if you take a traditional rigid heatshield and all the other weight penalties, frequently quoted at 15% since Zubrin pulled that number out of his admittedly informed ass (aeroshell, restricted dimensions, restricted CG and CP positions, whatever), that margin should be enough to build a stout reusable vehicle with.
And further, I would add, since the landing requirement for Mars is by far way more complicated (thin atmosphere, supersonic retros required), landing the whole thing on Earth is more or less a “free thing” if you want to do it. Depending on the cost of orbital refurbishment between mission and the launch costs, that may or may not make sense. Just for the sake of completeness, I must add aerobraking into orbit needs better precision than straight reentry.
As to the other points you raise, well, I wouldn’t mess with a tankage that I have to refill in Mars again (wet lab idea). Just in case I bang into a valve or puncture something, you know.
I also want to point out the phenomenal cosmic coincidence of both legs of the journey having approximately the same delta-v requirements. Kind of a “wow” moment that reinforces the neatness of the concept in my mind.
That sounds tinker heavy lifterish not saturnish to me. multi core tugs with main core that goes to orbit.
Well, if 350mT to orbit doesn’t bring to mind the biggest operational launcher ever produced (with many apologies to Energia), we work in different ways 😉 That’s what I meant, you can use your own mental label (HLV, SHLV, BFR, big sonova… you get the idea: BIG).
Steve (I answer here ’cause of the reply limitation):
Well, in a remote future we can’t be more in agreement, but the sad truth of the matter is that all that orbital infrastructure for propellant propulsion, transfer and storage, is at the moment nonexistent. We don’t even have a decent tanker on service, or anywhere for that matter!
So faced with “build it yourself or don’t use it”, you can kind of see how a single item development (reusable transfer vehicle from earth to mars and back to earth’s surface) can be, well, doable for a single company where other options are pie-in-the-sky ideas the just can’t deliver. One single new machine to build, after all, and you can have all your support infrastructure close to home, and most of it will exist already. Seems real world to me, no matter how sci-fish the spacecraft sounds (and it sounds pretty Heinlenian to me).
Ernesto, AKA Rune… in case you saw me somewhere esle. Have a nice day!
Tinker no time to read all your replies to this, but i wanted to say this. If your have a ship from mars fly in and you want to refuel it with methane, don’t your need to get a big agraculture space station up there that has a byproduct that is methane? Don’t we need a spacex methane 6 tug version of tinkers tanker to build such a station?? Isn’t Spacex going to mars anyway?? Isn’t this a way to use Elons little mars coloney mission to kick off a space economy?? if you are going to fuel mars missions with methane don’t you want to grow some food with it first??
My Tick pilots are ready Mr. Tinker (STEEL MEN/WOMAN in space) building real estate to fuel the future.
PUT IT IN THE PLAN MR. WHITFIELD!!!!!
Oh Tinker
IF your made a methane version of your heavy lifter wouldn’t it be easy to make the tugs or main tank run on either fuel, depending on the use in space?
For real estate apps put oxygen in the main to orbit tank
methane fuel depoT apps either methane or oxygen
All you would have to do is switch a valve or tWo right?? Since the volumes are about the same.
Time to start planning to fly some S#$% up there.
JOE Q FARMER
DTARS:
Go to the head of the class! If I used methane fuel in my MegaLifter™ launch vehicle idea, then I guess whichever has the smaller volume goes in the Tugs because the purpose is to maximize useable volume lifted to orbit.
Folks:
For those of you that may have missed it, MegaLifter™ was an idea I came up with over a decade ago. The two goals were to get 500mt to orbit using a reusable launch system and to maximize the useable pressurizeable volume launched on each flight. I needed the volume to build a rotating space station but that’s another story.
Here’s what you do:
First some terms: An ‘Engine’ is a rocket motor or motors providing a unit of thrust. The ‘Core Tank’ will be the center tank of the stack that will be our ‘real estate’ going to orbit.
A ‘Tug’ is a reusable stage made up of a tank, Engine or pair of Engines plus recovery system.
Now the concept: The unorthodox idea here is to split up the rocket fuel and oxidizer into separate tanks. The core tank would be huge, carrying all the fuel or oxidizer the six Tugs need. Each Tug would have a tank carrying ⅙ (one sixth) the volume of the fuel or oxidizer needed, a much more manageable size when recovery is considered.
The MegaLifter™ Launch vehicle would be made up of a Core Tank surrounded by six Tugs. The Stage One and Stage Two Tugs would each have two Engines while the Stage Three Tugs would only have one Engine each plus hardware for orbital operations. The Stage One Tugs would cross feed to the Stage Two Tugs while the Core Tank feeds all six Tugs.
The Flight Profile: MegaLifter™ is a three stage launch vehicle, each of the three pairs of Tugs acting as a stage. The Core Tank would mount on a launch table, the Tugs clustered around it. For sake of example, lets call it an eight minute flight to orbit. At launch, all six Tugs light up, Stage Two Tugs feed off Stage One Tugs (in pairs) while the Stage Three Tugs have enough fuel or oxidizer in their tanks for the full eight minutes. The Stage One Tugs and Stage Two Tugs gulp the Stage One Tugs tanks dry in just two minutes so the Stage One Tugs are jettisoned for recovery. The Stage Two Tugs with full tanks can continue to burn for another four minutes before dropping away for recovery. The Stage Three Tugs carry the Core Tank to orbit. Once the Core Tank is delivered to it’s costumer on orbit, the Stage Three Tugs reenter for reuse.
Each stage Tug would probably need different recovery systems. The only requirement is that they carry the Engines and have the tank volume. Each stage Tug could look quite different.
Did I mention payload? It is after all supposed to be a 500mt launch vehicle. First off, because the Core Tank goes to orbit by default, the payload can be put underneath the Core Tank. A cylindrical canister would be a far better volume to fill and the canister itself is even more real estate on orbit once it’s emptied. The Core Tank can thus be made much lighter because it only has to carry light cryogenic liquid. You could make a reenforced Core Tank and hang all sorts of payloads around it above the Tugs. One idea I had was to have 18 capsules in three tiers of six above the Tugs, each capable of carrying 100 passengers. That’s 1800 folks to orbit in one launch! Each capsule would have launch abort capability and be recoverable. I call it the Emigrant Launcher.
My original design was based on liquid hydrogen and oxygen using the SSME (x30) and RS-68 (x20) as baseline engines but the concept would work fine with methane too. The only change is that the Core Tank would be much smaller (almost half the volume of hydrogen) regardless of whether it made more sense to put the liquid oxygen in the Core Tank or not.
As with my original design, the Tugs (all stages) would need the tank volume a Space Shuttle External Tank oxygen tank. Not unreasonable considering SpaceX’s Grasshopper program.
What do you think, especially Ernesto?
tinker
is the same talk where Elon trashes space based power sats?
I have no audio at the moment
it seems to me if Elon is right then a solar based power sat would make a great solar smelter to melt down NEO’s
Steven,
In this talk, Elon looks at all energy usage and generation technologies in terms of efficiency — how much do you get out (usable) for a given amount of input. That argument kept bringing him back to the Sun as the most important energy source, and he believes solar cells are the best Earth-based power generation system looked at simply in terms of power output per square unit of land usage (for example, nuclear power plants need a lot of safety space around them, whereas solar cell can go on your roof).
In this talk, he doesn’t really get into SPSs. The feeling I got was that he didn’t really like the idea, but he didn’t have solid argument for why not, like he did with other systems, such as bio-fuel (which he dismisses as very inefficient in terms of output/land use).
Steve
Folks:
Here’s a page with another lecture and an interview from Elon Musk’s trip to London:
http://media.aerosociety.co…
tinker
Folks:
Here’s another little tidbit about SpaceX from the NewSpace 2012 conference held last summer; a video with a different landing scenario for Dragon then previously shown (starts at 32 minutes in):
http://www.youtube.com/watc…
tinker
Musk is the first person in the business who seems to actually understand the economics of reusable vs expendable LVs. As he points out the fuel for the F9 launch only costs $200K, about .3% of launch cost. He wants to switch to methane because it is cheaper than RP-1! TMK virtually no one within NASA knows how much the various rocket propellants cost, let alone why the ratio between propellant cost and launch cost is important. I would be happy to hear from anyone with a differing viewpoint, but maybe part of the reason both NASA and ULA have been unable to reduce launch cost is because they have no incentive to do so.
Who died and left Elon Musk in charge of everything space????
Dannsci:
It’s not so much that somebody died, more like somebody carelessly left the space baton just lying around and nobody contested Elon Musk when he picked it up. Sad but true.
I think it’s been lying there since Von Braun dropped it almost fifty years ago. In plain sight too so don’t complain! 🙂
tinker
JTT,
Not complaining, just making a point that you quickly picked up on. I am a supporter of the SpaceX approach, for the most part. I suppose what I was really driving at is that there is a little of a Musk, a Von Braun, etc, in all of us. Let us not let another 50 years get by us.
dannsci:
My comment was tongue and cheek so no worries. Sometimes it takes an individual to get big things done. Not single handedly of course but with the right people, the right resources and the guidance. wonders can and have been accomplished. It is a precarious path but a path none the less.
“If it’s a horse race, I bet on the best horse to finish first but if it’s a one horse race, I bet on the horse to finish!” – tinker
tinker
the Space baton lololololol
good choice of words lolololol
“Who died and left Elon Musk in charge of everything space????“
dannsci,
In truth, pretty much everybody else on the planet.
Lots of people have been talking up a storm for years. Musk actually did something. We should be both grateful and inspired to follow in his footsteps.
Steve
If my company gets bought for a few billion dollars, I promise I’ll build cool stuff with it too.
Elon says material to build a rocket is 1% of the cost.Close to my calculation of $10 a lb. empty.H e also confirmed that he builds sheet metal rockets not machined plate which he sounded like he was dismissing.If Elon and Reagan Hero Worshipers use him to say private is the way to go,he disagrees with you.H e said it would be fine with him if a government put a person on Mars first.Of course he said he was going to land a person on Mars in 10-15 years,so it does not worry him to say that.I would feel more kinship to a USA government mission.It is our NASA.If he can do it quicker,that would be fine too.I hope he can do it.
He said he had plans for a Rail Gun crossed with a Concorde.Somebody with more imagination than I,might want to say what that is.
http://www.flightglobal.com…
interesting?
DTARS:
Stratolaunch and SpaceX part ways
Why am I not surprised. For one thing, I don’t think liquid launch vehicles have a future for air-launch. To many fiddly bits for an otherwise elegant system. My guess is they’ll wind up using solid fuel in composite airframes like the solid boosters of the Delta IV and Atlas V, only bigger. It’ll be no crew launcher then.
tinker
Ernesto:
“I also want to point out the phenomenal cosmic coincidence of both legs
of the journey having approximately the same delta-v requirements. Kind
of a “wow” moment that reinforces the neatness of the concept in my
mind.”
Just how exactly do both legs have ‘approximately the same delta-v requirements’? Are you talking about the ‘Earth to Mars’ leg starting after first stage seperation? The return ‘Mars to Earth’ leg from the Martian surface to Earth’s surface (or Earth orbit)?
I do see how return to Earth’s surface makes sense. By ‘free ride’ you mean most of the energy to slow down is absorbed by friction through the atmosphere so no fuel required except for final approach and landing. Not having to rely on orbital operations at all reduces orbital infrastructure costs to zero. Also, if the first stage cores are reusable than relaunching the MCT back to Mars still only costs fuel, refurbishing and restacking.
I’m beginning to like it.
Do you have any idea what the tank volumes for this hypothetical reusable Mars ‘ferry’ (because that’s it’s closest analogy, it just has a booster stage at the beginning of the Earth leg) would be if it were burning methane and LOX? It would give me some idea of it’s size. If you know the mass ratio of the fuel/structure I’d know how much dry mass to play with (is that what you meant here?: “This single stage I talk about, with MR 5, can be just 80% fuel, 20% everything else. Call it the MCT if you want an acronym. ;)?)”.
I think Elon has given us enough clues to reverse engineer the concept in general terms. Shall we have a go?
tinker
Hi!
Well, by similar delta-v requirements I mean that, taking full advantage of aerodynamic deceleration, LEO-Mars surface comes to about ~6-7km/s propulsive capture, and probably supersonic retro-propulsion included. And from Mars’ surface to LEO, again using the atmosphere to brake but capturing and doing the terminal landing with engines, takes about the same amount. It has to do with LMO orbital velocity being around the same as a Hohmann TMI injection (first order of magnitude-speaking here, of course).
About the reusable Mars ferry (i think the internet has stuck the Mars Colonial Transport name to it, ’cause someone at SpaceX mentioned MCT as an acronym), yeah, I meant it comes out to about mass ratio 5. YMMV, up to maybe 7 in a worst case, but I’ve been so generous elsewhere I just went with 5. Seemed an elegant number. Total mass, of course, depends on a lot of different assumptions, from payload to inert fraction, with the aerobraking systems mass ratio being a very important thing. And of course the mass of the tankage and its volume all depend on those. But considering Methane’s density is more or less the same as oxygen’s, calculation are surprisingly easy on size, once you pick your assumptions.
I think I’d rather wait a few months to hear more concrete numbers from the horse’s mouth, but if you want to play around, I usually pick a conservative 10% of the fuel carried for long-term mild cryo tankage, and assume that takes care of engines, structure, and avionics and the like. Deciding what your payload is is also important, and Transhab, a habitat designed for just such a mission duration for a crew of six, clocks in at about 35mT. Stick a more-or-less arbitrary percentage for aerobraking systems like 15% of the total aerobraked mass on top (in this case, I went the super-safe way of budgeting almost 15% of IMLEO, not just to be safe, but because I was running the numbers in my head while I was listening to the lecture), and there you go, mars transportation system. Just go find your launch vehicle!
I got to 350mT IMLEO, with a 35mT Transhab-equivalent on top of a 35mT methane stage/heatshield, but as you can see that is a very rough, not even back of a napkin analysis. I’m sure you can do better!
P.D: IMLEO: Initial Mass at LEO
Ernesto:
So, 70mt of spacecraft carrying 280mt of methane and LOX?
If the delta v is equivalent for both legs from Earth orbit velocity then we can assume probably a two stage launch vehicle carrying the fueled MCT at least that far. From there, it can initiate the Mars transfer burn directly during launch or from orbit. The same vacuum nozzle of the MCT’s main engine(s) should work fine at Mar’s low atmospheric pressure for the return trip, shouldn’t it?
I don’t think Transhab will cut it for a spacecraft that has to deal with two separate reentry profiles so we’ll have to assume a rigid structure. Being large and almost empty during entry to Earth or Mars atmosphere has gotta be an advantage. All we have to go on in the past was a very high mass Space Shuttle pushing the limits of reentry. These spacecraft will have a much lower mass to surface area.
Because of the need for cryogenic storage during the cruise phase (both ways) we can assume the fuel/oxidizer tanks will be built inside the craft so they can be properly insulated. Thus, the ‘hull’ could be made completely from lightweight composites. This type of construction could survive dozens of flights so the initial much higher cost could be offset by many years of use.
Interestinger and interestinger…
BTW: Do a search on this page for MegaLifter™ that I talk about in a previous post above. I’d like your opinion.
tinker
Exactly, you seem to get the essentials and the implications (especially the low ballistic coefficient when empty). The only thing where I might correct you is in that inflatables, counter-intuitively perhaps, turn out to be more sturdy for the same mass, or lighter for the same structural strength. They can also be heat resintant, but the main point is Transhab is there to get a mass reference on payload, nothing more. The most efficient distribution I can guess is some kind of big squat cylinder, with hab on top, then the fuel tank, then heatshield, engines and landing gear and such on the bottom. KISS, which usually means an efficient design.
As to your MegaLifter. Well, everybody has their pet idea, don’t they? I sure have a couple of mine. The only difference is some get built, most don’t. Perhaps sometimes even depending on inherent merits! 😉
My general advice is to familiarize yourself with the rocket equation and run it extensively to get the real mass distribution and delta-v of each stage, since it’s the only way to know how optimized that rocket may be (and where and when staging happens). Siamese and triamese designs aren’t know for their staging efficiency (the effective mass ratio of each stage during their flight), and what you suggest looks like something similar in the way it behaves. After that, you will either revise it, abandon it, or present a much more solid and defined design… like one where you actually choose a propellant perhaps? Difficult to evaluate otherwise ;P
Other than that, well, I wouldn’t know what to say really. Points that do come to mind are that separate tanks for fuel and oxidizer is a concept that has been explored and used (only both being in the same stage, but conceptually, same difference). Also, if you have similar pressures and temperatures, it is way more structurally efficient to use single tanks with a flimsy intertank bulkhead.
Perhaps most importantly, what you seem to get at is sacrificing payload to lift empty tankage in the end. That may be cool if you like large diameters or you plan to reuse that tankage as real estate, but in general, limits the design, and there ARE existing workarounds for both real estate and limited launch vehicle diameters. Most involve inflating stuff, as you can guess.
Ernesto:
The whole point of the MegaLifter™ is to dispose of the maximum weight possible at each staging event. Regardless of whether the Tugs carry oxidize, fuel or both, at each staging event a proportionate number of engines and tankage gets jettisoned leaving just enough engines to carry on. Stage One engines burn for two minutes, Stage Two burns for six minutes, Stage Three burns for the full eight minute flight. All three Stages ignite at launch so no engines are carried as dead weight for any part of the mission except for the orbital operations engines on Stage Three. So I guess that’s the real concept, three stages in ‘parallel’ instead of in series.
It was the master of Single Stage To Orbit, Gary Hudson, that put me onto the numbers that showed that a three stage launch vehicle was the most efficient design for maximizing payload to orbit. Running the stages in parallel saves on dead engine weight and incremental jettison of tank volume saves more. I’m not the best at numbers but I ran a simulation back when of my MegaLifter™ design based on hydrogen as fuel and RS-68 engines. I got a whopping 8% of my Gross Lift Off Weight (GLOW) to orbit (barely). I ran known designs on the same simulator as baselines so I know I was close anyway.
Is that clearer?
tinker