SpaceX Grasshopper Flies High(universetoday.com) |
SpaceX Grasshopper Flies High(universetoday.com) |
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...
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.
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.
[0] http://en.wikipedia.org/wiki/International_Traffic_in_Arms_R...
OTOH, his pal Peter Thiel is pretty extreme. That's someone I'm not comfortable with.
They do plan on retrieving the stage if possible, it should float.
Thank you.
The RCModelReviews youtube channel has a number of good videos on basic RC concepts (not multirotor specific, but the RC stuff still applies).
One tip I'll give you is to look into getting a Eurgle/FlySky/Imax/Turnigy 9x Transmitter (different brand names, same basic Chinese knockoff..). It's a solid radio with a lousy stock firmware, but there are a number of good open soruce firmwares out there that are very easy to flash onto the controller (especially if you use something like the SmartieParts programming board). For ~$100 (for the radio plus the programmer) you end up with something that rivals radios costing an order of magnitude more (or so I've heard... I've never touched a high end radio).
I'm approaching the hobby in stages:
1) Buy a Blade mQX (which comes with a cheap transmitter) and learn the basics of flying a multirotor
2) Get a 9x transmitter, mod it, and learn how it works
3) Get a 'JR compatible' OrangeRX DSM2/DSMX module for the 9x, so you can bind it with the mQX and get used to flying with the full size 'real' tranmsmitter
4) Get an 'ARF' (almost ready to fly) kit (this should include the frame, ESCs, motors, props, etc), and a flight control board (I'll probably start with something cheap like the Kk 2.0). This is a good time to learn things like "What is an ESC?".
5) Start modding your ARF quad (replace the ESCs, add a camera, get a more capable flight controller (like the Arducopter), etc)
6) Build something from scratch
I'm currently on step 3, researching step 4.
There are many ways to start into the hobby. You can get yourself a radio and a simulator and learn to fly on the computer first. You could go for an off-the-shelf solution like the DJI Phantom that will fly very well without much tuning or fiddling (but it'll cost the part). Or you can go the DIY way - a good keyword is "MultiWii", it's a fairly cheap but rather labor-intensive way of getting your first copter to the skies.
And the 1970s one weighed a lot more than 3.52 oz!
All these things could have been done earlier if the politics was different.
DC-X used F-15 gyros / guidance with some software tweaks for example.
Love this, totally making it mine ;) Also, there is the problem of efficiency loss due to over/underexpansion as you switch from atmospheric to vacuum conditions, and I have never heard of a rocket engine with variable nozzle geometry to compensate for it.
You have a lot of information, but I understand that putting all of this in a xls would be a lot of work.
Nuclear rockets would be so awesome if they weren't so nasty.
There's about 90% as much gravity at the altitude of the ISS.
It's the atmosphere (and associated gravity drag), not the 1/r^2 scaling, that does it.
I've been playing too much Kerbal Space Program, I assumed the first stage had already reached orbital velocity.
One way this is done is by making Kerbin a lot smaller than Earth. Specifically, over ten times smaller. This reduces the speed needed for low Kerbin orbit to around 2000m/s, while low Earth orbit needs around 8000m/s.
A factor of four in speed probably already sounds bad, but it's much worse than one might naively expect. The amount of fuel needed to accelerate a given payload to a particular speed grows exponentially with the target speed. A typical rocket engine exhaust velocity, both in KSP and real life, might be 4000m/s. When the target velocity is half the exhaust velocity, as is the roughly the case with Kerbin, then you need about 40% of your rocket's mass to be fuel. In other words, you can orbit about 60% of your total mass. When the target velocity is double the exhaust velocity, as is roughly the case with Earth, you need 86% of the initial mass to be fuel, so you can only orbit about 14% of the rocket.
In other words, if you're putting 1000kg into orbit, then in KSP you need about 700kg of fuel, while on Earth you need over 6000kg of fuel. For a single stage rocket, that 1000kg that you're putting into orbit includes fuel tanks and engines. You need much bigger engines and fuel tanks to lift 7000kg than you do to lift 1700kg, so a lot of that 1000kg you get into orbit is going to be empty fuel tanks and spent engines, not actually useful stuff.
Staging lets you work around this problem by letting you reduce the amount of useless junk you put into orbit. By dropping large amounts of empty fuel tank and spent engine early on, you no longer have to lift it all the way up, and you have more orbited mass left over for actually useful widgets.
A single stage that goes from ground to orbit isn't too hard in KSP. On Earth, it's right at the limits of technology. Nobody has operated a rocket as a single stage to orbit, but a couple of pieces of larger rockets are theoretically capable of reaching orbit from the ground on their own if flown by themselves. It's possible, but the amount of useful payload that such a thing can put into orbit is so small that it's not cost effective.
That's a moderately ironic statement, given the fact that SpaceX wouldn't be doing anything remotely close to what they're doing today without the very large contract they got from NASA.
This is how NASA was able to spend over 30 years and $30B trying and failing to develop a new orbital vehicle, where SpaceX was able to do it for under $400M.
Atmosphere is slowing you down as you go up as well, so lift off requires fighting that as well. Therefore the energy you've expended is not entirely stored in potential energy. (Fun fact: If it weren't for the atmosphere, rockets would actually take off almost horizontally. They go up at first to get out of the thickest air before going sideways.)
The craft is much lighter, because it no longer has the payload, and also has used almost all of its fuel.
Right.
At take off, the delta vee is the escape velocity PLUS all the losses due to friction, which are tremendous.
At landing, the delta vee is only equal to terminal velocity. EDIT: Okay, plus some flying time on top of the landing point.
I think there are a few major, mostly technological, developments which haven't happened yet but are essentially inevitable which will tend to tip things even stronger toward the "good" side. I should probably write about that at some point.
http://www.boeing.com/boeing/commercial/747family/pf/pf_400_...
Parachutes (and associated equipment) are heavy, so you'll burn fuel lifting that extra weight.
Parachutes are complicated, and would be an extra system to develop, test, and validate.
Parachutes are annoying to repack/replace (increasing turnaround time).
Parachutes put odd stresses on large objects when they deploy (increasing the amount of inspection you would have to do after each flight).
All that hassle to reduce the terminal velocity by a couple hundred miles an hour. That's not that big a win for a pretty high cost.
What if you have a payload container that was the size and weight limits of the second and third stage, which was put up into LEO by the first stage. The payload would then be picked up by vehicles already in orbit, and the first stage unit returns to earth.
Assuming that the payloads are simply building materials, to be assembled by bots in orbit....
You'd still have to refuel their reaction mass, unless we are talking solar or magnetic sails.
That is where you will find the best info for the space industry more than likely. A lot of the info is in the forums though and you will have to kind of hunt it down. They also have a private section of the site that you can pay to gain access that has a lot of insider info.
Except the first stage doesn't run out of propellant does it, because it has to LAND again. Hence my puzzlement.
I know why multi-stage rockets are used... I'm asking why this rocket needs them, since they solve a problem it doesn't have by design.
In fact you can kinda make a rocket that can reach orbit that doesn't have "stages" but rather jettisons engines themselves. Early Atlas rockets did this: they had one set of fuel tanks but two engines. About two minutes into the flight they would jettison one of the engines.
This is where you're incorrect. Not having to accelerate the empty first stage to orbital speed (and back!) is a huge fuel savings.
If you need more payload build a bigger rocket.
You could also add wings to the rocket and fly it home which has it's own set of trade-offs and benefits(see space shuttle).
And because you don't know whether it is damaged or not (sometimes the damage may not be obvious), it's likely that the rocket will have to get a long post-flight inspection to check if it is suitable for another flight. It's something you can almost completely avoid if you land the rocket gently.
I read somewhere, that the costs of recovering SRBs of Space Shuttle from the ocean and then inspecting and fixing them were many times greater than building another pair of boosters.
Plus, parachutes create a new failure mode: parachute deploying when it shouldn't.
I think you might mean m/s? low hundreds of km/s is very supersonic. ;)
I meant kph, which was HOPEFULLY obvious from context.
I'll just leave this here: http://www.smbc-comics.com/?id=2679
Political, because it was the Space Race, and a lot of it was about shows of force. And hey, why not? You have a bunch of carrier battle groups just waiting around for a hot war, and you need to have them out training anyway, so why not use them to pick up spacecraft from time to time?
Technological, because guidance wasn't necessarily very accurate. It's interesting to look at the miss distances here:
http://en.wikipedia.org/wiki/Splashdown_(spacecraft_landing)...
Some of these landed hundreds of miles from their target. However, by the time Apollo came around, they were all very close. You definitely want a big recovery fleet to cover a lot of area when you can't be sure it'll land on target, but that's not so much of an issue these days.
That's the TLDR. The delta-vee from the parachute is not worth the trouble.
In short, same basic reason why we use wings and wheels to land airplanes rather than dropping them from a parachute when they reach their destination.
First off, if the goal is to save fuel from having to do a propulsive return to the launch site then that's not going to happen (except for the 2nd stage and capsule). The US has a lot of sparsely inhabited land but it doesn't have the same huge swathes of uncared for steppe that Russia/Kazakhstan have where they can just dump spent rocket stages everywhere with nary a care. There are range safety issues there that can't easily be avoided. Second, a giant rocket stage coming down on just parachutes is going to be damaged more on land than at sea. If you're trying to avoid the weight of landing gear you're just going to end up with the rocket engines crunching into the ground, which isn't going to be good at any speed. OK, so you can't save RTLS fuel, and you can't avoid having landing gear, at that point the only difference is a tiny little dribble of fuel to bring the stage in for a controlled powered landing. So you might as well just do that and be done with it.
Something as big and 'light' as the F9 first stage will be slowed down tremendously by the atmosphere. No need to add all the extra complexity and weight of parachutes.
Also, part of the allure of SRBs is that they are cheap to manufacture, comparatively (this is a false savings, due to increased operational complexity, but it's still very tempting), so even if a significant amount of money could be saved per SRB through reuse it wouldn't have affected the cost a launch much.
The cost of launching a Shuttle including the amortized development costs ended up being $1.5 billion per launch.
It's more like wanting the companies that make them more profitable by requiring no retooling. I don't buy the "it's about the workers" thing.
