SpaceX’s Autonomous ‘Grasshopper’ Rocket Makes Milestone Flight
wired.com
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Blue Origin is a bit ahead here in terms of take off and landing. But it has the challenge of not benefiting from a paid launch contract like SpaceX currently has.
What I find particularly interesting is that either the Dragon or the Blue Origin craft already have the delta-V to land an return to orbit from the moon, if they can get there. The thing that will break that wide open is on-orbit refueling. The game changes in a particularly compelling way when you can launch "gas cans" to orbit and refuel existing craft that are already in orbit. Not only does that extend the life of satellites but it enables Multi-launch configurations. United Launch Associates gave a pretty compelling talk about how they would meet some of those challenges in their long duration vehicle paper: http://www.ulalaunch.com/site/docs/publications/Integrated%2...
Exciting times, 20 years late but still.
It is a shame that NASA and congress didn't decide to go the DC-X scale up route back in the '90s instead of heading down the X-33/VentureStar rabbit hole.
I have not seen proposals for on-orbit cryo fuel transfer. But I'm sure they are out there.
Keep in mind no one has successfully done powered vertical landing from orbit. It's never been done. (Well, not from Earth orbit anyway. The LEM landed vertically from lunar orbit.) SpaceX is getting a taste of how hard this is by trying to recover their first stages using parachutes - their every attempt to do so has failed.
If they could focus the bulk of their engineering workforce on this problem they might be able to do it faster. But they have to massively scale up production to meet the orders they've taken, they have to keep their reliability up, they are constantly working on performance upgrades for Falcon 9's engines, and they have to get Falcon Heavy going to crack the DoD market. Oh, and there's this little thing called Dragon and NASA's Commercial Crew program. Something about launching those living sacks of meat and bones we call people tends to hold your focus pretty intensely.
http://www.space.com/13140-spacex-private-reusable-rocket-el...
I'm sure they'll start with just the first stage, but you can't just do a powered descent - that would leave it in the middle of the Atlantic ocean. It has to be a return-to-launch-site maneuver and landing, which is what you see in the video linked to above. At the point where the vehicle does a 180-degree turn (referred to as a "death swoop" by rlv enthusiasts), it's going Mach 6 and is 1000 miles downrange. That's hard.
What SpaceX is doing is totally awesome but – for the foreseeable future – a risky business.
Source: http://forum.nasaspaceflight.com/index.php?topic=30385.msg10... (and generally a good place to look for SpaceX updates...)
There's a Grasshopper 2 plan in the works (using a v1.1 tank) which will supposedly have rather more flight-like legs than the current one.
But I'm sure that a lot of what they've learned from Grasshopper will be going into the June test.
For a relight, you need some propellant at the feed pipes to restart, though if you have small enough aero forces, you could just vent some stuff to accelerate the rocket forward slightly so you can start ingesting liquid again, instead of the pressurant gas and can then proceed with relight.
Then again, since the empty rocket's bottom end is heavy, it could orient itself the right way aerodynamically anyway (acceleration vector pointing the way of the nose) so the liquids go towards the engine end.
If it comes like a dart and not tumbling (which presents its own problems), such a big stage has lots of mass per frontal area and it will come in quite fast.
Interesting aerodynamic problems. I wonder if we might see some maneuverable mini fins or wings at some point.
One hindering factor is the problem of having enough fuel to make the return trip.
There needs to be a better technology to harvest the massive amounts of energy wasted when decelerating from 30k mph to 1 thousand mph during re-entry. Convert the heat to a usable fuel. So we store the fuel needed for re-entry in the velocity of the craft.
A heat to fuel converter. If we could be 100% efficient at this, we would land with just as much fuel as we left to get into orbit.
Or, in the case of of Mars, we can focus on in-situ resource utilization [1]. Zubrin's Mars Direct [2] is built around this, and there are some immense fuel savings to be had [3].
[1] https://en.wikipedia.org/wiki/In-situ_resource_utilization
[2] https://en.wikipedia.org/wiki/Mars_Direct
[3] Zubrin, Robert. The case for Mars. Free Press, 1996.
> But a fully reusable rocket could change the equation dramatically. Musk illustrated the point by citing SpaceX's Falcon 9, which costs between $50 million to $60 million per launch in its current configuration.
> "But the cost of the fuel and oxygen and so forth is only about $200,000," Musk said."So obviously, if we can reuse the rocket, say, a thousand times, then that would make the capital cost of the rocket for launch only about $50,000."
Direct link: http://www.space.com/13140-spacex-private-reusable-rocket-el...
You can read about the Gas-Generator Cycle for rockets here: http://en.wikipedia.org/wiki/Gas-generator_cycle_%28rocket%2...
Basically, a small amount of fuel and oxidizer are bled off into a gas generator and used to power the turbines that feed the fuel and oxidizer into the rocket engine.
The cryogenic fuel is piped about the "outer surface" of the rocket's nozzle and combustion chamber such that these essential structures doesn't melt away under the pressure and heat.
I do find that a brave integration -- using fuel as a coolant.
Not an engineer in this field, but I'd imagine using fuel flow as coolant makes for a lighter-weight engine overall, even as it might complicate control system software, and might place narrower limits on, or complicate stability control of the engine's net available (throttable) range of power.
Just speculating here, but perhaps a single engine's power range limitation becomes another reason (along with graceful system degradation, without mission loss, under single engine loss) for SpaceX's multiple engine designs for their larger rockets? Switch off additional engines as rocket weight decreases (due to fuel and oxidizer usage) during descent? Doubtless there is a great difference in total mass between take-off weight and landing weight, so it would seem to require a lot less fuel & oxidizer to land it than to lift it to orbit.
Also wondering about ablative heat-shield placement and arrangement for re-entry, first and second stage.
The fuel is used as coolant since it's a better coolant than the oxidizer for a range of reasons. One of them is that hot oxygen is very corrosive. Also, because of that a small oxygen leak from the coolant passage to the chamber tends to grow larger with catastrophic consequences. With kerosene the problem is coking.
Yes it's more complicated to design a regenerative cooled engine, but existing materials can't take the heat. Some maneuvering thrusters are heat sink designs. Some engines are ablative, with things like evaporating carbon taking the energy.
Yes it only needs one engine for landing vs nine for fully laden takeoff.