SpaceX CRS-3 launch scrubbed due to helium leak
new.livestream.com
new.livestream.com
Their most recent test went pretty well all things considered. For the first time they tried a "death swoop" maneuver, turning the 1st stage 180 degrees around as it was starting to re-enter and refire some of the engines to slow it down. It picked up a nasty roll though and centrifuged the propellant, cutting the engines prematurely. They recovered some debris but that's about it.
It's hard to overstate how big a deal it will be if they pull this off. But the odds of success are very low, given the propensity of these things to tumble and roll on reentry.
The data from the last launch provided a lot of really crucial information that has informed design decisions made for this and following launches.
It's actually better if the next recovery fails too, at least if it happens in a way that provides really important data. This would then let them work out the engineering and science required to improve the design further.
This test isn't expected to be successful, either.
http://www.spacelaunchreport.com/falcon.html
http://www.spacelaunchreport.com/falcon9.html
http://www.spacelaunchreport.com/falcon9v1-1.html
https://en.wikipedia.org/wiki/Falcon_9#Reusability
These guys made the system:
http://www.airborne-sys.com/pages/view/spacex-falcon-1-and-f...
https://www.youtube.com/watch?v=kJrFwxE3lzI
Is this video incomplete? Will both the 1st and 2nd stages will actually require re-entry shielding?
If you know the first stage mass, relative to the lift off mass, you can compute the energy needed to decelerate it to 0 from what ever velocity it reaches at separation. Because fuel is a significant component of the launch weight, you need significantly less fuel to return the nearly empty stage than you did to put it up there to begin with.
There's no hard and fast definition of how high/fast you need to be going for it to count as a "re-entry", but that certainly qualifies.
https://en.wikipedia.org/wiki/Mach_number
If anyone knows anything about the how the first stage is shielded, I'd be very interested to know. In the artistic video, you can see a quick peak of the nose of the first stage. It's colored tan/yellow like the heat shield on the second stage, but there aren't many details. (Presumably, this was purposefully vague.)
The engines on a rocket are designed to withstand huge amounts of heat. It may be the intent is to have the rocket re-enter engine first. I'd love to see more information on that part of the rocket myself. Certainly interesting :D
Atmospheric drag is then going to provide most of your deceleration, slowing you down to terminal velocity. You then make another burn at the very end of the flight to slow down from terminal velocity and stop.
The second stage is a good example. After making a deceleration burn, it will be re-orienting so that the heat shield at the top is facing the direction of movement. It will then keep this orientation until it is safe to orient the vehicle around for landing.
You could use your engines for most of the deceleration... but it would consume a very large amount of fuel. No point in doing so when you already have atmospheric drag to do the work for you.
That animation for the second stage reentry is an animation. Recovering the second stage will be extremely difficult and, if it is ever done successfully, I don't think it'll involve doing a 180 flip in the lower atmosphere.
I don't think (?) this altitude and speed requires heat shielding for the 1st stage. The 2nd stage is jettisoned far too fast and high to make recovery feasible (for now!).
[1] http://forum.nasaspaceflight.com/index.php?topic=27748.690
((3 529.6 * 1000) / (60 * 60)) / 340.29 = 2.88120263
http://new.livestream.com/spacex/events/2833937/statuses/480...
Next attempt will be April 18th.
Because you're using helium-3 as a dilution refrigerant, and you've made it sufficiently low pressure that the stuff just diffuses through your massively thick stainless steel container and into your vacuum vessel - at a low rate, but it does.
How is that?
Hydrogen atom is one proton + one electron [1], and "Helium is composed of two electrons bound by the electromagnetic force to a nucleus containing two protons along with either one or two neutrons, depending on the isotope" [2]
Helium has more protons, thus more nuclear charge. Its valence electrons are in the same shell but are being "pulled closer" by the protons, so the total diameter of nucleus + electron shell is "smaller."
The reality is, of course, much more complex. Here's Physicsforum (generally a good source) teaching more:
In manned flights to low earth orbit, since the spacecraft reenters, at least that part could be reused.
The second stage is hard to reuse because it flies so far downrange horizontally and reenters at very high speed. The engine also can't run low in the atmosphere, meaning somehow different recovery than for the first stage.
The parts of the spacecraft that are not heat shielded (service module) will be sacrificed, but in the future the whole spacecraft might be a monolithic entity or even part of the second stage and do its mission and reenter and land as a whole.
The second stage is meant for use in a vacuum so it's expansion nozzle is much larger, so perhaps that extra weight would balance things out a bit, but I suspect that the second stage would have a massive thrust/weight ratio when reentering almost empty. Makes things more challenging, even if the engine does work in atmosphere correctly.
Launch time is 20:58:44 UTC (16:58:44 EDT), and of note, this launch will be deploying over a hundred femtosats, and will be SpaceX's first attempt at first stage vertical landing (over water).
http://www.spaceflightnow.com/falcon9/009/status.html
NASA live stream (higher resolution than above):
http://www.ustream.tv/nasahdtv
SpaceX live stream:
If I remember correctly, it wasn't until the space shuttle solid rocket boosters that NASA managed to recover a 1st stage. SpaceX is a lot younger.
Also of note, the space shuttle missions were the first "reusable" systems. SpaceX is just starting out and they are already attempting it. Very cool!
The leg frame on Grasshopper looks massively over-engineered, which is fine for a test vehicle but would be far too heavy for an actual launch vehicle. We have still to see the final leg design, and the ones in the CGI mockup video look, to my untrained eyes, very skinny. Grasshopper has proved the basics of the maneuvering and landing capability, but there's still a fair way to go.
But the landing legs on the Falcon 9 first stage don't have to carry the weight of fuel fuel, never mind the weight of the second stage and payload and their fuel -- it launches from a pad and the legs only carry the dry stage at landing.
The empty first stage is bulky, but relatively light.
The real question in my mind is how much extra fuel it takes to re-light the first stage motor after separation and decelerate it to the point where it can land vertically. There's got to be quite a weight penalty in there. (Which AIUI is why the second-gen Falcon 9 first stage tankage is 30% bigger than the original. Fuel is cheap compared to precision engineering.)
Twin jets have enough thrust for single engine ascent with full fuel. This necessitates a huge rudder. But the planes live with that.
Jets may be able to engine-out climb with full fuel, btw, but they can't necessarily land with full fuel.
I'm pretty sure the landing legs will be fine if they can pull off the controlled burn and keep the rocket spin under control. The last time they tried this (without legs) the falcon 9 spun too fast in the atmosphere damaging the in tank baffles so that the fuel centrifuged causing the engines to go out on the second burn.
We have photographs of the actual production legs (folded away) on this current F9.
https://pbs.twimg.com/media/BlIDkwYCUAAiWXz.jpg:large https://pbs.twimg.com/media/BlL4V42IYAAgZ1J.jpg:large
I believe the plan is that the first launch of a new first stage would be used for manned missions (once they get to that point) and then subsequent launches would be used for satellites and such. Presumably going for cheaper and cheaper satellites as it ages.
Apparently the name Grasshopper was just the name of the rocket during the tests, because I can't find that term used anywhere.
http://www.nasaspaceflight.com/2014/02/spacex-crs-3-landing-...
That's awesome. Such a short time from initial testing to actual use.
I wonder if they have a buoy or something for it to target.
In software terms it's as though they have deployed reusability but kept it behind a "feature flag" which keeps it turned off for most uses, for now. Once they gain more confidence in actually flying reusable flight profiles using stages that include landing legs then they will eventually work their way to returning to land at the launch site.
They launch from the coast to the east (taking advantage of the Earth’s rotation), meaning when the first stage shuts off it will be somewhere over the Atlantic, on a ballistic trajectory further eastward. Since the goal is to be re-useable without losing too much payload capability I really don’t think they can have much fuel to spare at that point. To decelerate and come to a hover, sure, that’s the goal, but to actually decelerate, accelerate in the opposite direction, decelerate again and come to a hover? That would be ridiculous.
SpaceX will need to launch from somewhere else to end up over land when the first stage shuts off.
Nope. The long term plan is for the 1st stage to return under its own power to the original launch site.
https://www.youtube.com/watch?v=kJrFwxE3lzI
They claim that a big part of reducing costs is eliminating recovery operations that made the nominally "reusable" solid-rocket boosters on the shuttle so uneconomical.
This self-post on /r/spacex describes how it could/would work. Basically the guy modded KSP to hell for realism (realistic fuels, more realistic aerodynamics, realistic earth and launch site inclination, etc) and managed to fly the first stage up and then back to the launch site: http://www.reddit.com/r/spacex/comments/1z6vyt/boostback_dem...
@mikeash (posting is throttled for me at the moment):
The rotating earth isn't providing any sort of mechanical advantage for the returning first stage (unlike during liftoff). However it does move the launch site closer to the rocket.
Very rough numbers: earth rotates at about 1000mph at the equator, so if we fudge florida down to the equator and assume stage separation is at t+3:00, then in the elapsed time between launch and stage separation, the launch center has moved 50 miles to the east. In the subsequent minutes up until first stage touchdown, it will move even further to the east.
Consider that just launching from the equator straight up to 35,786km would not put you into into a geostationary orbit; you would fall back down to the west of your launch site. If you went straight up, while initially moving at the same horizontal velocity as the ground from which you launched, you would not maintain the same surface-relative velocity; you need to speed up going east to do that. The outside of a record moves faster than the inside of a record.
Reaching orbit while launching to the east is easier because orbital speed counts in a non-rotating frame, but it doesn't matter at all (except for minor centripetal effects) for the case of landing back at your launch site.
Edit: sorry, but your pseudo-reply continues to commit that fallacy.
You're right that the rotation of the Earth moves the launch center 50 miles to the east in the time between launch and stage separation, assuming that happens at 3 minutes. However, it also moves the rocket 50 miles to the east. Net result is zero.
Imagine doing this in a gigantic train car. You launch a rocket to the end of the car and then have it come back. Does it matter which way the car is moving? Of course not. The roundness of the Earth complicates it a bit, but not much at these speeds and altitudes.
You do, in fact, maintain the same surface-relative speed as you go up. Well, until you move sideways enough that the Earth's gravity exerts a significant sideways force, but that's not going to be significant for a while. In any case it is gravity, not the rotation itself, that causes that. You need to speed up to maintain the same angular velocity as you rise, but not your linear speed relative to the surface.
The rocket, not on the surface, still has that 1000mph extra kick that the earths rotation gave it, but it is above the earths surface and therefore must move faster than 1000mph to keep up with the earth. (Of course it is moving _much_ faster than 1000mph, but the point is that while the rotation of the earth gave it 1000mph, that 1000mph does not keep the rocket above the same position once it is up there).
To understand why you don't maintain the same surface-relative speed as you go up, consider geostationary orbit again (where the numbers are extreme enough to work out intuitively):
Sitting on the launch pad, the geostationary rocket has a "bonus speed" of 1000mph, which is enough to put it stationary over the ground. The surface relative speed, with this 1000mph, is 0, which is your objective for geostationary orbit (~35k kilometers directly above the launch pad).
So all it needs to do is go straight up, right? Wrong. While 1000mph is enough speed to keep up with the earths rotation at sea level, it is nowhere near fast enough to keep up with the earth at ~35k kilometers. It needs to go up ~35k kilometers and it needs to move ~5867 mph faster to the east in order to keep up with the same position on the earth. If you were up at 35k kilometers and moving east at 1000mph, the same speed as the ground is moving at sea level, then the ground would be whipping by you as it rotates underneath you. Plotted on a map, you would appear to be moving very quickly to the west.
Example: If snakes are a type of tree, then snakes are plants. Snakes are a type of tree. Therefore, snakes are plants.
There isn't a logical error here, but there is a factual error. The incorrectness comes from bad input, not bad reasoning.
The eventual plan is to accomplish the maneuver with a total of three burns. Shortly after separation, the first stage will reignite three of its nine engines to decelerate enough that hitting the atmosphere won't break it apart. This is a fairly short burn, and they have done it on at least one flight so far.
The second burn, which they haven't tested yet, will use the same three engines to boost the stage back to the site where it launched from.
Finally, they will ignite just the center engine shortly before it hits the ground in order to land softly. It can't hover. Even with the engine throttled as low as it will go, the TWR is still >1, so no hovering...
SpaceX has published all sorts of information about their Return to Launch plans, and a simple googling should reveal that. They're even put out some shiny promo videos demonstrating the process.
It just seems weird to me that this fluke of geography would force them turn around and land. It seems like they could launch in Texas or somewhere and then land in Florida or something.
The other advantage to boosting back to the launch site is that any failures result in the first stage crashing into the ocean. If you put it on a ballistic trajectory towards Miami... the worst case scenarios get a lot worse...
The Rocket Company has other similarities with SpaceX. Kerosene open cycle engines. Aluminum construction with friction stir welding. Company started by dot-com tycoons.
My understanding (from watching Scott Manley's KSP videos) is that Kerbin's atmosphere is amazingly thick near sea level and that a real-world rocket should start its gravity turn much lower.
It could easily tip over and explode, similar to what happened to NASAs vertical landing rocket.
http://www.space.com/23193-spacex-grasshopper-rocket-highest...
This is an incredibly significant step, and crucial for the long-term vision of cheap space-travel through reusable vehicles.
They are otherwise identical, so "nearly" is just confusing here.
Nonetheless I think describing GMT as "nearly UTC" isn't particularly helpful, since it's not defined accurately enough to be wrong. Furthermore, EDT is defined in terms of UTC, so there's no reason to mention GMT at all.
You'd probably burn as much fuel recovering from the parachute's meandering miles off target as you would just slowing the ballistic final leg. (not sure though, -ENOMATH)
Parachutes are very useful when you don't have engines powerful enough to slow you down, but the whole purpose of this is the controlled landing of nine very powerful engines.
It doesn't have to be a gentle landing, there's never going to be any people on board. It just has to not come apart in the process. A very high-g hard-stop could be cheaper in terms of weight than a giant parachute.
You probably know of the Model T, but don't know the first combustion engined car. Choose the MPMan, or the iPod for history? Who had more direct impact on the American Continent, the Spaniard, Columbus or the British Mayflower?
Not saying I'd agree, but there's at least a reasonable rationale.
After we have cheap & reusable rockets we'll have much larger leaps in space travel in the next 40 years than we have since the 40 years since Apollo.
The Apollo program was conceived in 1960, before either the suborbital flight of John Glenn or the earlier orbital flight of Yuri Gagarin. Before we had successfully built and tested a rocket capable of putting a single man in space, we started a space program with the goal of putting a man on the Moon, which would in the end involve launching a three-man spacecraft, with sufficient fuel to carry it to the Moon, manually reconfiguring it in flight, flying it for three days through the void, entering orbit around the Moon, detaching a portion of the spacecraft to land upon the Moon under manual controls, bouncing around the Moon in space suits, goddamn driving around the Moon in little cars (later missions), flying the space craft back into lunar orbit, rendezvousing with the orbiting spacecraft and manually re-docking, flying the ship back three days to Earth, and re-entering the Earth's atmosphere and landing safely.
And they did it in under 10 years. SpaceX turns 12 this year.
As for landing on another planet, in order to get to Mars, SpaceX has to first get a reliable means of putting resources into orbit. Being able to recover rockets means there is less time spent building new rockets and more time spent building the thing that ends up going to Mars.
Being able to power-land a launch vehicle in an atmosphere means that it should be possible to power-launch a landing vehicle designed to land on another planet with an atmosphere as opposed to simply landing on the vacuum-exposed surface of the Moon.
So yes, from an engineering perspective this is bigger than the Apollo program, and from a human resources perspective this is bigger than the Moonshot. Doing more with less: this isn't about dollar economics, it's also about material and labour.
When SpaceX starts their Mars mission, they won't be using anything like the Saturn V. That rocket solved the problem of launching a mission to the Moon by throwing brute force at the problem. SpaceX is approaching the problem with more finesse and more advanced engineering.