http://www.youtube.com/watch?v=sWFFiubtC3c
This will give you an idea of how grasshopper fits into the full flight plan.
Perhaps it is the innovation of never seeing a rocket do a full-blown take-off and then land vertically and then seeing what the long-term result will be - which is orders of magnitude better and more efficient than how it is today....that just gets me excited.
But I am truly glad to be alive today and glad Elon Musk is who he is....and doing what he is doing.
In 40 years, if he continues on his current trajectory, my kids will find it weird that space travel was "novel" in my generation.
That's VERY exciting.
Imagine if somebody replaced your car with a version that had twice the carrying capacity, but would only run for one tank of gas. It wouldn't be a worthwhile trade would it?
Additionally you can build more expensive rockets that are more efficient since rocket creation becomes a capital rather than a reoccurring cost.
Upon landing, the atmosphere does most of the slowing-down for you, so you only need enough fuel to reduce the speed from terminal velocity (not sure what this would be for a rocket, probably several hundred miles an hour, at least) to 0. So, I'm sure it's not an insubstantial amount of fuel, but maybe less than you'd think?
http://youtu.be/vDwzmJpI4io?t=27m
(Watch from 27m for about 50 seconds.)
I wonder if a combination parachute/thruster landing would be more feasible though? Sort of like the Mars Science Lab without the sky-crane.
> "The payload penalty for full and fast reusability versus an expendable version is roughly 40 percent," Musk says. "[But] propellant cost is less than 0.4 percent of the total flight cost. Even taking into account the payload reduction for reusability, the improvement is therefore theoretically over a hundred times."
As it is in that video, it's having to carry engines and fuel for 3 separate stages, for no apparent reason.
The rocket equation is a harsh mistress, it demands exponential amounts of fuel the faster you want to accelerate a given stage (specifically, as a ratio to the exhaust velocity of the rocket). Given that orbital velocity is quite high (about 8.5 km/s) relative to the exhaust velocity of the best chemical propellants (about 3 km/s for LOX/Kerosene) this results in impractical mass fractions to contend with (17:1 to get to orbit, and that's with no payload). But you can cheat. If you use staging and drop away the dead weight of empty fuel tanks and no longer needed engines from lower stages then you can make an end run around the rocket equation. You make a rocket that can accelerate a payload up to a certain velocity, then you make an even bigger rocket which can deliver the entire other rocket as a payload to a different velocity, and so on, until the sum total of all the velocities is the necessary total speed you require to get to orbit.
We're actually fairly close to being able to make single-stage-to-orbit (or SSTO) launchers workable, but it's a difficult problem. We can just about make a single stage with a high enough mass fraction to do it, but then there is almost no payload remaining. And the only way to make a vehicle with such a tiny payload cost effective would be to make it reusable, but enabling reusability would add additional weight which would destroy any payload whatsoever and probably prevent it from even reaching orbit, catch-22. Potentially we could use advanced engines, rocket fuels, and lightweight materials (like carbon fiber) to build a reusable SSTO which would have a reasonable payload, but such designs are hugely untested and very risky. So for now the best hope for reusability seems to be to incrementally advance the design of existing multi-stage rockets.
1) During the late stages of the boost, the one second stage engine is pushing only its single engine, fuel and tankage. You're no longer dragging around the nine engines of the first stage and their tanks. That weight saving means you get a lot more delta-V for each unit of expended fuel.
2) The engines themselves are also different. Rocket nozzles designed for optimal performance at sea level aren't optimal for high-altitude or vacuum conditions; those optimal for vacuum won't work at sea level (their exit pressure is so low that the exhaust has trouble pushing air out of the way). And compromise designs aren't optimal in either environment.
3) In the proposed SpaceX reuse architecture, they don't need to protect that long, thin first-stage tank from re-entry at orbital velocity. It's not clear how they could.
Single-stage rockets need to carry a lot of dead mass (empty tanks and engines) all the time, and that is a lot of wasted fuel. A multi-stage rocket can dispose the big first stage engines once it's cleared out most of the Earth's gravitational pull and use smaller engines to continue.
Another important consideration is that rocket engines don't run optimally during the whole burn. The first stages are optimized for atmospheric conditions, whereas later stages are optimized for vacuum conditions. Therefore having one big engine propel you up all the way incurs in an even grater loss of fuel due to the inefficiency at high altitudes. You could probably have a rocket engine capable of having a variable geometry to compensate for this but AFAIK is almost impossible to do it.
See the following for more details:
[1] http://en.wikipedia.org/wiki/Staging_(rocketry)#Advantages [2] http://en.wikipedia.org/wiki/Rocket_engine_nozzle
Check out the video on this page for a good view of what that process looks like: http://www.extremetech.com/extreme/149741-spacex-falcon-9-la...
It also reminds me that when it comes to science, and who knows, maybe other things as well, it's not just public sector vs private sector. SpaceX wouldn't be driving us forward like this if NASA hadn't put in a whole heap of groundwork first, but similarly NASA have other goals to worry about besides keeping costs down. It's that combination of NASA's huge ambition and private enterprise's drive to make efficiency savings that will eventually get us colonizing places that aren't the Earth.
I hope it happens in my life time,
First, you need a massive government program to get the technology from the pie in the sky stage to something usable - a multi-decade, arduous process that produces no short-term profits, if any. Once that's done, it's time for the private sector to step in.
Here's a short link to bypass: http://www.ssyoutube.com/watch?v=sWFFiubtC3c
https://jobs.github.com/positions/bd54ba2a-a930-11e2-9c0e-5c...
The very next Falcon 9 flight (out of Vandenberg) will use the performance overhead provided by the v1.1 upgrade to do a controlled reentry of the 1st stage and then after it has reached terminal velocity it will slow down to a hover out over some remote part of the ocean, then splash down. This is a good and cheap test of a huge part of the flight profile. Meanwhile, the Grasshopper 2 will be more of a full-up Falcon 9 (v1.1) first stage, with 9 engines and will include retractable landing gear. Instead of testing controlled hovering and precision landing it'll go up to supersonic speeds and potentially up to 90km altitude. Essentially testing the return to launch site flight profile in a more realistic setting with more realistic hardware.
And then if that proves fruitful they will essentially just stick that hardware into the Falcon 9 stack and do a full up orbital launch with a flyback 1st stage. Possibly within the next few years even. If that works it'll be rather amazing, since much of the cost of a launch is in the manufacture of those 9 engines on that first stage. Even if a reusable stage costs 3x as much as a regular stage and halves the payload capacity if they can get just 6 flights out of each one it'll break even, and if the numbers are more favorable they'll drop the floor out of the orbital launch market and then own it, to the tune of tens of billions of dollars a year in revenue (a feat they are already on their way to doing with their current lineup of rockets). Perhaps more profoundly it'll hasten the day when it will be conceivable to use kickstarter to fund an interplanetary science mission.
If you don't mind me asking - where did you find all this out? I've been looking for a good source of SpaceX news. The official website/g+/facebook/etc just posts short updates whenever a mission occurs. I'm looking for news about what is on the horizon and more detailed analysis.
Seems to me that this would yield an even better test "for free" and even provide the possibility of recovering the first stage for analysis.
I'm a bit worried about the bimodality of the future but man the good parts are going to be good.
Could you explain the first part a bit more, or point me somewhere? How was is the first stage going? Does it need a heat shield?
EDIT: Ha, looks like a lot of people had the same question at the same time.
edit: Can't find it at the moment. So far I've found http://en.wikipedia.org/wiki/McDonnell_Douglas_DC-X which did what grasshopper and more almost 20 years back. I still believe I've read something earlier though. Will edit when/if I find it.
The DC-X program, and others like it were spawned by private industry who were betting on a huge 'single stage to orbit' (or SSTO) model for satellite launches that would be needed for the Reagan 'Star Wars' missile defense program. They died when Star Wars died and NASA briefly assumed control of DC-X when its private backers pulled out but was stretched too thin to give it any real push.
That said, Elon and others will tell you that the current crop of rockets would not be possible without the work that NASA did and has shared. SpaceX also has benefited from computer systems that are 10,000X more powerful than the ones that NASA had available for their use, and materials that are 1/3 to 1/2 the weight and yet stronger than their NASA counterparts. Sensors that are 100x more sensitive and 1/1000th the cost. A six degree of freedom inertial unit was $125,000 in 1970 and resolved differences of .1G. A 9 degree of freedom unit from Sparkfun Electronics [1] is now $125, and reliably resolves 1/4096'th of a G. So I don't doubt that the same engineers at NASA could build what SpaceX is building today, today, but I assure you they didn't have the tools to build it back in the 70's or even in the 90's.
There was an AMA with several of the software teams a little while back:
http://www.reddit.com/r/IAmA/comments/1853ap/we_are_spacex_s...
There are several openings right now for software engineers, including people with web experience (people usually don't think we're looking for those skills):
https://jobs.github.com/positions/bd54ba2a-a930-11e2-9c0e-5c...
I'm sure SpaceX's hex is big, powerful, and carries all sorts of nice toys, including having enough lift to carry an HD camera and stabilizer - but still, it's not that complicated to make one. I could probably make an HD-camera-carrying hex myself if someone was willing to sponsor the parts - including stabilization for the camera, onboard controller for extra smooth flight, etc. And I'm not a rocket scientist. :)
You want a hex for this sort of job because you can lose one rotor without crash-landing your sensitive HD gear. With a quad, you lose a rotor, the whole vehicle crashes.
If you build it yourself, you could put together a video platform like that for under $1k (including the gyro stabilized camera gimbal).
http://www.armadilloaerospace.com/n.x/Armadillo/Home/News?ne...
Version with different music. Heard it works in other countries.
Wikipedia have an article about it:
http://en.wikipedia.org/wiki/Blocking_of_YouTube_videos_in_G...
>So, I think, there's a number of improvements across the board, in structures, avionics, engines and then, as I said, this version [the Falcon 9 1.1] is really designed to be able to have the first stage come back - boost back – to launch site, deploy landing gear and actually land propulsively.[1]
With a flyback stage the optimal separation altitude and velocity drops, and the second stage gets even larger to compensate. But yes, the engine will cancel the downrange component of velocity and reverse it. Since the stage is empty the fuel requirements are actually quite modest.
[1] http://shitelonsays.com/transcript/crs-2-post-landing-teleco...
"The rocket exhaust is directed into a flame bucket or trench. The flame trench is designed to redirect the hot exhaust to a safe direction and is protected by a water deluge system that both cools the exhaust and also reduces the sound pressure level (loudness). The sound pressure level of large rocket engines has been measured at greater than 200 decibels — one of the loudest man-made sounds on earth."
Maybe for fire-fighting? Seems a little close for that though, if something went wrong it could be in the middle of it. I can't think of anything else though.
Edit: Maybe it feeds some sort of un-manned fire suppression system? That would be pretty smart.
Only time will tell.
