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Discussion in 'SpaceX' started by sjoshuaj, Nov 10, 2013.
I had an idea. Want to get peoples' opinions on feasibility of the idea.
Such an interesting name that I had to go look.
Tutorial:Asparagus Staging - Kerbal Space Program Wiki
Interesting idea, but surely a single large cylinder has a much higher volume to mass ratio then a bunch of smaller cylinders? If you're trying to reduce cost per pound surely that's a factor? Also if you're trying to bring these things back to Earth and land them, it's going to be easier with one big rocket rather than seven small ones...
Maybe one of the reasons for development of new methane rockets is SpaceX's stated goal to fly to Mars.
Using methane makes sense since it can be manufactured on Mars combining hydrogen and carbon dioxide to create methane and water. This
means the return vehicle would refuel on the Martian surface. One disadvantage is that method is harder to ignite but SpaceX should be able to address that in time.
The new rocket also will do well in the vacuum of space needed for the long flight to Mars with a reported thrust of 300 metric tons, about 4x the thrust of Merlin 1D.
SpaceX's Mars rocket to be methane-fuelled
Theoretically "a bunch of smaller cylinders" could be more efficient. Reason for that is a fuel cross feed. So whole rocket is powered by fuel from two cores, then those are detached. Then next two cores are feeding fuel to central core and then detached. Essentially you are getting multistage rocket that do not drag extra mass higher and higher.
That is the idea behind Falcon Heavy. But no one tried it so far and would be interesting to see how cross feed would work in practice. Anyhow, after SpaceX launch FH for a few times they would be in excellent position to develop even more complex schemes of cross feed, like one shown above.
It may be possible to do something like this, but I don't see why you wouldn't want to also develop a new engine if you can improve performance.
Complex staging also has its own costs and can increase the chances of total failure of the launch.
The other thing to keep in mind is reusability. If we want to truly become a space fairing civilization, we need all of our rockets, including the boosters to be reusable, that means that after they separate they would need to land successfully and be attached to the next core, refueled, and be ready to go. Ultimately it may be better not to use heavy launch vehicles for the bulk of launches, and only use them when absolutely necessary. It is much easier to land one core and one second stage than it is to land 6 boosters, and a core and a second stage.
It may be better to design systems for long term use in space that can be assembled in orbit, small enough to be carried by a single, smaller, simpler rocket and multiple launches.
For colonization of Mars, it might take one launch of a large vehicle to shuttle people back and forth, but when it comes back, it will need to be refueled, and have passengers carried to it.
Never thought of it, but once they go fully reusable it'd be fun to watch a Falcon Heavy launch. First you get a major launch followed by three separate landings of the initial stages Might develop a queue so indeed would be a tougher challenge as you need three separate landing pads.
Kind of an old video from January 2013 about Falcon Heavy, but one I hadn't seen before. 38mins.
I think the video is actually much older, sometime in 2011?
very reasonable configuration..
I'm not sure to what degree there is a parallel, but the old Russian N1 suffered some serious development problems because it had 30 engines arranged in 5 clusters of 6. At a minimum, the potential for destructive harmonics would seem to still be there. One the positive side, I think the N1 only had one oxidizer & one fuel tank, which probably made feeding the 30 engines more difficult than in the scenario that you've shown - where the you have multiple independent systems.
from Wikipedia -
i love how KSP logic is being applied to real-world rockets...
Wouldn't it be super much more expensive? If they make the asparagus-config, trying to land all booster-stages would require extra engines on all the stages. More engines=higher cost? Make your arguments why not.
Each booster stage would presumably have all the engines it needs -- just like the Falcon 9 uses 3 of its 9 engines for a braking/reversing burn up high, then a single engine to renter the thick atmosphere and again to finally land. It certainly requires more propellant though.
But I think the plumbing interconnections and valves between so many booster stages, along with mechanical changes on at least the core booster to support the weight/thrust, and detachable structural links to hold them all together, may be more trouble than its worth.
More engines equal more mass production. Another advantage is that is easier for someone to work with because each engine is much smaller. It is much easier to transport. If there is a problem with one engine it would be much easier to replace a single smaller engine than a massive engine. It is probably easier to tweak the specifications of a smaller engine to adjust performance than a much larger engine.
The Russian RD-180 is a really big engine.
Those are just a few reasons off the top of my head...
A four-engine airplane is typically less reliable than a twin engine airplane, simply because there are more engines to fail. They tend to be more expensive to maintain, thus the recent move to really huge twin engine designs.
On the other hand, the loss of one engine in flight is a less serious situation when you have four. For that reason for many years twin engine airliners were not allowed to do long haul cross-ocean flights. The DC-10 had a third engine kludged onto the tail when the designers realized it couldn't get certification for extended range operation over water.
Of course for a rocket the tradeoffs are probably more complicated.
Another benefit is any improvements made to the design of the Falcon 9 can be easily carried over to the other Falcon Heavy configurations. While with two or more rocket sizes there is more work involved in scaling the improvements.
The Falcon Heavy's second stage is already lacking in delta-v. Example FH needs a kick stage for Solar Probe Plus mission. Your design would need a new Hydrogen or Methane engine and a upper stage to be any helpful.
Asparagus needs multiple staging events, and SpaceX wants minimum number of those as possible. HF will not use the propellant crossfeed in first missions (if ever), and crossfeed would be extra complex with Asparagus design. If you have Methane engine, why not use it also in the first stage? With a single big first stage you get rid of those multiple staging events.
This is moot anyway, we know that next SpaceX launcher is BFR with ten meter core and full flow Methane engine; Raptor.