SpaceX lands a rocket

[Brovane]

Not taking anything away from these guys as it's one hell of a feat, but McDonnell Douglas / Uncle Sam did this 20 years ago in the early - mid 90's. Nothing came of it then, and I doubt anything will come of it now.

https://www.youtube.com/watch?v=mn6iHzcTEoA

http://en.wikipedia.org/wiki/McDonnell_Douglas_DC-X

Realistically the main reason that the DC-X died was because NASA wasn't interested in it, it was competing with the X-33 venturestar project at the time. Also funding was cut and NASA wasn't interested in finding more funding since it would compete with the big bucks X-33. So after the test vehicle had a accident it was convenient to let the entire thing die. It wasn't really a issue with technology or feasibility. It was just lack of interest and money.

 

[Brovane]

Unfortunately, the Chinese will probably steal their secrets and sell it back to them for a sizable profit.

Actually it is funny you mention that. Musk has mentioned several times his concerns with the Chinese and stealing secrets from Space X. This is why he doesn't patent a lot of the stuff that Space X is doing. Basically his theory is that a patent has no bearing if your main competitor is a foreign nation. The only thing a Patent does is give the foreign nation a easier blue print for how to steal the technology from Space X.

 

[Brovane]

That's pretty badass. But it also seems woefully impractical. Wouldn't it necessitate a rocket taking up an exponentially larger quantity of fuel than is currently required to enter/break orbit? Where are you going to store it all? Or am I misunderstanding the point of the demonstration of a rocket that can land itself?

Relevant.

No it doesn't require that much fuel to break orbit. All you need to do is decelerate a little and you start dipping into the upper atmosphere and your speed starts dropping as you start hitting more air molecules which drops your speed even more which means hitting more air molecules. For most the descent the deceleration will not be by rocket engine it will be by air molecules. As the vehicle hits more and more air molecules it decelerates all on its own. This is where all the heat comes from which is the air molecules hitting the vehicle and slowing it down. Left to its own the vehicle will slow down to less than 300mph just because of terminal velocity limits as the air gets thicker.

However remember that Falcon 9 is a two stage rocket. The 1st stage when it burns out it hasn't achieved orbital velocity. The test vehicle you see in the video is just focused on the 1st stage which never achieves orbital velocities. So the 1st stage is a easier to work with and it is also where a lot of your costs are. Think 9 engines on the 1st stage and only 1 on the 2nd stage.

This is a great vehicle that illustrates the concept of how air will slow down the 1st stage as it drops back into the atmosphere.
http://www.youtube.com/watch?v=2aCOyOvOw5c
The SRB at separation are going around 3,000 mph and they slow down to less than 300 mph when the chutes pop. All that is handled by the atmosphere slowing things down.

From my reading Space X is expecting to lose about 20% in total payload to LEO with a reusable rocket. However even with a loss of 20% the Falcon 9 v1.1 can still put over 10 tons into LEO.

 

[grohl]

I did the same thing in Jupiter Lander

 

[JulesMaximus]

dude owns tesla, hes working on electric rockets probably

Yeah, trouble is that they run out of fuel 30 seconds after liftoff.

 

[Ventanni]

I could see this capability being much more useful when mining the moon, as they won't be able to easily rebuild rockets out there like they can on Earth. How they plan on getting all the fuel out there though... well that'll be another engineering challenge

 

[andylawcc]

Not taking anything away from these guys as it's one hell of a feat, but McDonnell Douglas / Uncle Sam did this 20 years ago in the early - mid 90's. Nothing came of it then, and I doubt anything will come of it now.

https://www.youtube.com/watch?v=mn6iHzcTEoA

http://en.wikipedia.org/wiki/McDonnell_Douglas_DC-X

hopefully Elon has his team will think of something useful out of it

 

[Zeze]

unobtanium for the cable, having to construct a massive anchor or haul a small asteroid to use as one, etc. definitely not easy either, but in theory the economics would actually be feasible for mass use.

I used to work in telecom (cell towers). 500' guyed towers utilize 15-20 cables to support them.

Engineering wise, I don't see you need some unearthly material for the cable. You just need more spreading across a big radius.

Space begins at 264,000 feet, which is roughly 50 miles. Low earth orbit begins at 525,000 feet (100~ miles) which is where satellites operate.

Roughly based on similar physics guyed cable scheme, it shouldn't take more than 150~ miles of diameter clearance for space elevators. This should be an easy feat in US alone- we have fvckton of land in TX and the entire midwest.

 

[sunzt]

For those uninformed about the goals of spaceX, the company is aiming to drastically reduce the cost to orbit and have currently made great progress with their falcon 1 and 9's by reducing launch costs by ~ a factor of 10.

The next step is to build a rocket that can land itself so you don't have to pick it up, ship it back, and set it up. So you ultimately launch a mission, deorbit and land back at the launch area. Check the vehicle, fill it up, and launch again.

The descent isn't going to be relying on thrusters alone, most of it will be with a parachute and the final burn will be with thrusters.

 

[Howard]

I used to work in telecom (cell towers). 500' guyed towers utilize 15-20 cables to support them.

Engineering wise, I don't see you need some unearthly material for the cable. You just need more spreading across a big radius.

Space begins at 264,000 feet, which is roughly 50 miles. Low earth orbit begins at 525,000 feet (100~ miles) which is where satellites operate.

Roughly based on similar physics guyed cable scheme, it shouldn't take more than 150~ miles of diameter clearance for space elevators. This should be an easy feat in US alone- we have fvckton of land in TX and the entire midwest.

Those guy wires only help with bending stresses. The compressive stress would be insane.

 

[Murloc]

very cool, that thing must not be easy to control.

 

[pandemonium]

Spent sooo much fuel just to land back, holy cow.

I do agree what for now, what is the point of this? Rockets are optimized for going one way. A real shuttle would've landed just fine like plane.

This thing spent so much energy just to land back upright. Stuff like this actually made me realize how primitive we are in grand scheme of space travel.

The point is the fact that even shuttles abandoned their rockets & tanks. The major cost of launching isn't the fuel, it's the apparatus. A lot of the rockets that are used to launch are failed to be retrieved, are salvaged, and can't be used again, so the cost of launches are astronomically large for the loss of the apparatus (which includes high amounts of engineering time required, as well as materials).

 

[slayer202]

can anyone explain the significance of this vs. everything else accomplished in space travel, landing on the moon, or even spacex sending supplies to the ISS? I'm sure I'm missing something

oh nvm, I read the 2nd page of replies

 

[Juddog]

Pretty impressive for a non-government entity to be able to do this, especially considering their budget.

 

[Paratus]

I used to work in telecom (cell towers). 500' guyed towers utilize 15-20 cables to support them.

Engineering wise, I don't see you need some unearthly material for the cable. You just need more spreading across a big radius.

Space begins at 264,000 feet, which is roughly 50 miles. Low earth orbit begins at 525,000 feet (100~ miles) which is where satellites operate.

Roughly based on similar physics guyed cable scheme, it shouldn't take more than 150~ miles of diameter clearance for space elevators. This should be an easy feat in US alone- we have fvckton of land in TX and the entire midwest.

Just getting above the atmosphere isn't enough. You'd still need to accelerate to orbital velocity. So you'd still need a smaller but still large rocket.

A space elevator is supposed to have it's center of mass anchored in orbit, which means a Geostationary Orbit at 22,300 miles out. To counter balance the pull of gravity the elevator would need to extend another 22,300 miles or have a large weight above it to counter balance. At 22,300 miles the natural tangential velocity is orbital speed.

So you need really strong materials. Carbon nanotubes could hypothetically work.

 

[Exterous]

Yeah, trouble is that they run out of fuel 30 seconds after liftoff.

Next up - recharging stations on blimps