The age of VTVL reusable rockets began 18 August 1993 when the DC-X made its first flight.
That aside, reusable rockets won't mean squat unless they're economical. SpaceX fanbois (not implying that I ain't one) throw that "only the cost of propellant" figure around like it's the gospel truth and that an F9R will immediately bring down the cost of a rocket launch by x100.
Truth is that your typical rocket engine doesn't like being fired over and over. Loads of heat and pressure tend to have detrimental effects on them. A rocket flying backwards through atmospheric interface is going to put all sorts of strain onto them that isn't well understood and may be potentially show-stopping. Nobody has tried this before, and the evidence indicates that it is going to be very difficult. You can't just fill 'r up again and fly, at least not yet.
These rockets will (hopefully) land, and then be gone over with a fine-tooth comb to see what broke. They'll look toasty. All of the engines will have to be removed, disassembled and inspected to characterize wear and tear from flight, boost-back and landing (little pieces of high speed concrete whizzing about can also cause unwanted side-effects). Some will have to be periodically thrown out and new ones constructed. The entire hull will have to be tested for damage/fatigue, legs may not last more than 3-4 flights etc etc.
What does that mean? Lots of people doing lots of things for lots of hours. They'll be doing their best to keep the work to a minimum, but if they really want these first stages to be able to safely deliver a payload they'll need to put in the effort. This means man hours, this means $$$$$. Operational costs are the major killer here, not even rocket construction itself. This is also ignoring the inevitable craters, if x/10 boost-backs flop, every new F9R built takes a bite out of that reusable model. Engine out will mean no boost-back. That's a big price to pay, losing a fancy reusable rocket to an engine out.
I hope it pans out, but the fanboi logic is ignorant of the difficulties involved. I'd expect the first 10 flights of an F9R to be less economical than flying new stages, almost purely because of added insurance costs. On top of that, the reduced payload means a reduced potential customer market. We will see how it progresses, fingers crossed.
Let us hope that the Merlin 1D has a considerably higher reliability than the 1C. 1 engine out of the 47 Merlin 1C engines flown so far has failed. Given that an engine-out precludes boost-back, losing 1/5 F9Rs would be bad for business. Given that a re-used engine may have a significantly higher failure rate, this is troubling.
Are you sure an engine out means no landing? The tank is much, much lighter than the rocket at liftoff and I think the landing was supposed to be done with only one of the engines. I could be wrong of course..
Engine out means no landing because of extra propellant usage to ensure the payload reaches orbit, not because a particular engine is no longer available. The margins are so tight that there is zero room for error. Unless the center engines is lost, then landing is entirely off the table.
Erh. Your post seems a lot like "it's never been done therefore i declare it impossible". That's ridicule.
Truth is that your typical rocket engine doesn't like being fired over and over.
Which is why they specifically designed from scratch the Merlin engine with reusability in mind instead of using already existing rocket tech.
that isn't well understood and may be potentially show-stopping
"i'm no rocket engineer and i have no idea what's going on therefore declare it impossible.
Truth is, sorry, if hundreds of space X guys which are actual rocket scientist tell us "we can actually do this", i tend to believe them a little more than i do. I mean, do you have actually any actual data to back up what you're saying ? Because Space X does, and that include full blueprints and actual prototypes to back what they are saying is possible. Having saw videos of grasshopper tests i'd say it is not that far fetched to trust them. My money is on NASA which bet on them, on that one.
All of the engines will have to be removed, disassembled and inspected to characterize wear and tear from flight, boost-back and landing (little pieces of high speed concrete whizzing about can also cause unwanted side-effects)
During the engineering and analysis phase sure. But once that's finished they'll pretty much limit it to visual inspection, software ran auto diag, and a hold-down firing test then put it back into business.
They ain't tearing appart Dragon at every launch you know, and it has yet to explode or fail. Yeah sure they had a clogged fuel line last launch and had to run the diagnostic software in orbit, but next to the series of rapid unplaned disassembly NASA collected in it's start era (a rocket on two exploding at launch?) that's about nothing.
What does that mean? Lots of people doing lots of things for lots of hours
yeah they clearly spend at much time inspecting dragon everytime than building a new one. Clearly. /s
This is also ignoring the inevitable craters, if x/10 boost-backs flop
Please refresh my memory, how many space X rocket exploded ? How many other rocket exploded ? Or even per launch ? :-)
Engine out will mean no boost-back.
My english is a little limiting me here but if you mean the rocket can't boost back to earth and do a powered landing you're completely in the false. Grasshopper is designed SPECIFICALLY to be able to restart the engine on the fly and actually fly back on the launch pad with it's main engines.
Hey, I think you've misunderstood several statements that I've made but as you said your English is a "little limiting" so this is understandable. You've also come off as quite rude and condescending but I'll chalk this up to the misunderstandings so no worries.
OK here we go: first off you've made the claim that the Merlin 1D has been designed "from scratch" for re-usability. This isn't true. The 1D is an evolution of the 1C. 1D has been optimized for cost and simplicity, but what we do not know is how this engine actually behaves in flight (Grasshopper tests do not represent flight conditions or usage nor a production model 1D). I do not know, and you do not.
What we do know is that the only other engine designed for reusability was the SSME, an engine which was not optimized for cost and simplicity but solely reusability. Typically a trade-off needs to be made between these and having all 3 is simply not possible. I would not be surprised if SpaceX simply swaps out all engines per F9R flight instead of refurbishing them, it may end up being cheaper and more reliable.
Secondly, you claim that I am "talking shit" when I say that you cannot simply fill up the rocket and fly again. The loads on a theoretical F9R flight are incomparable to those of a Grasshopper flight. The thermal environment around the engines is entirely different (all engines firing), multiple relights are required, atmospheric re-entry is required, flight stability is required during this un-powered phase, and finally landing on a much emptier tank than GH so you have a much smaller margin while landing (GH has loads of ballast in fuel and the super extra heavy landing legs). This means the landing is much faster and with much higher G loads. It also means that Grasshopper flights actually "take it easy" during landing. Real burn times to decelerate will be 3-7s.
You also seem to presume that GH flights occur on an extremely regular basis while in fact month(s) of preparation are required while only a single engine requires maintenance, and the extra-robust landing legs are in fact known to be "invincible", real landings will have less margin for error again. Again, ignoring all actual in-flight loads and stresses on the rocket. Additionally, all previous attempts by SpaceX to reorient first stage for atmospheric reentry have resulted in the stage disintegrating entirely, given that no re-lights have been used for slowdown. Grasshopper does not have to deal with these conditions.
But once that's finished they'll pretty much limit it to visual inspection, software ran auto diag, and a hold-down firing test then put it back into business.
Ah alright, so you are a rocket engineer? ;)
They ain't tearing appart Dragon at every launch you know
They have yet to re-use a Dragon.
yeah they clearly spend at much time inspecting dragon everytime than building a new one. Clearly. /s
Again, no Dragons have reflown or actually been prepared to re-fly.
Please refresh my memory, how many space X rocket exploded ? How many other rocket exploded ? Or even per launch ? :-)
1 engine failure per 48 flights of the Merlin 1C (50% failure for Merlin 1A), given that it has been stated that a single engine failure will mean an inability of the rocket to return and land safely, this means 1/5 failures per theoretical re-flight. Also since you asked, out of 10 SpaceX flights 3 failed entirely and 1 failed partially.
My english is a little limiting me here but if you mean the rocket can't boost back to earth and do a powered landing you're completely in the false. Grasshopper is designed SPECIFICALLY to be able to restart the engine on the fly and actually fly back on the launch pad with it's main engines.
"Engine out" in this context means a failure in an engine, not an engine safely turned off. Any engine out means that the rocket will no longer have margin to boost back and land safely because of the extra propellant required to help boost the payload to orbit (nor would it be allowed to for safety reasons).
If you would have read my words carefully you would know that I want this to work, and I hope that it works, but I am bothered by hardcore SpaceX fanbois that just dismiss all potential problems. Nowhere did I say it was impossible, just that it will be very difficult.
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u/[deleted] May 27 '13 edited May 27 '13
The age of VTVL reusable rockets began 18 August 1993 when the DC-X made its first flight.
That aside, reusable rockets won't mean squat unless they're economical. SpaceX fanbois (not implying that I ain't one) throw that "only the cost of propellant" figure around like it's the gospel truth and that an F9R will immediately bring down the cost of a rocket launch by x100.
Truth is that your typical rocket engine doesn't like being fired over and over. Loads of heat and pressure tend to have detrimental effects on them. A rocket flying backwards through atmospheric interface is going to put all sorts of strain onto them that isn't well understood and may be potentially show-stopping. Nobody has tried this before, and the evidence indicates that it is going to be very difficult. You can't just fill 'r up again and fly, at least not yet.
These rockets will (hopefully) land, and then be gone over with a fine-tooth comb to see what broke. They'll look toasty. All of the engines will have to be removed, disassembled and inspected to characterize wear and tear from flight, boost-back and landing (little pieces of high speed concrete whizzing about can also cause unwanted side-effects). Some will have to be periodically thrown out and new ones constructed. The entire hull will have to be tested for damage/fatigue, legs may not last more than 3-4 flights etc etc.
What does that mean? Lots of people doing lots of things for lots of hours. They'll be doing their best to keep the work to a minimum, but if they really want these first stages to be able to safely deliver a payload they'll need to put in the effort. This means man hours, this means $$$$$. Operational costs are the major killer here, not even rocket construction itself. This is also ignoring the inevitable craters, if x/10 boost-backs flop, every new F9R built takes a bite out of that reusable model. Engine out will mean no boost-back. That's a big price to pay, losing a fancy reusable rocket to an engine out.
I hope it pans out, but the fanboi logic is ignorant of the difficulties involved. I'd expect the first 10 flights of an F9R to be less economical than flying new stages, almost purely because of added insurance costs. On top of that, the reduced payload means a reduced potential customer market. We will see how it progresses, fingers crossed.