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SpaceX Plans to Land Next Falcon 9 on Solid Ground

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Re: SpaceX Plans to Land Next Falcon 9 on Solid Ground

#121

Post by vectorjohn »

TeMPOraL wrote: post #108
toomuchtodo wrote: post #94

Earlier quoted context omitted.

I didn't spend the time searching google to provide citations, but it is feasible to generate fuel autonomously on the Martian surface and store it for future use. Can we launch a vehicle that will de-orbit, safely land, and then begin processing fuel using nuclear (edit: I removed solar here; solar would not provide enough power for such a facility) for power and the Martian atmosphere and soil as feedstock? Not qui…

From what I read around the Internet, they're planning on using methane-powered engines since methane gas is apparently present on Mars.

There's not enough to harvest. The idea is to make the methane.

http://en.wikipedia.org/wiki/Sabatier_reaction

Re: SpaceX Plans to Land Next Falcon 9 on Solid Ground

#122

Post by robotresearcher »

anigbrowl wrote: post #111
Cshelton wrote: post #8

I think now that they have proven they can 'hit the hole', almost spot on, they'll be able to get approval to go for a try on cleared land space. It sounds like to me, landing on land would be ideal; less expensive and less risk with stabilization and rough waters.

Landing is an awful lot harder than taking off, it seems to me; a single engine rocket with stabilizing jets is a bit like trying to land a pogo stick - possible, but inherently problematic. I know this must seem stupidly obvious, but I wonder if a better design for a reusable launch vehicle isn't 4 engines connected by a frame with the payload in the center, basically a chair. Yeah, it sounds horribly unwieldy with…

A frame with four legs is not self-stable in flight at all. The thrust on all four legs must be identical to prevent rotations, and rotations are not self-cancelling.

Quadcopters must be computer controlled because the control loop must be very tight. Humans cannot fly them without electronic attitude control. It is certainly no easier than the gimbal control of a rocket, which is similar to balancing a stick on your hand. We give that control problem to undergrads as homework.

Re: SpaceX Plans to Land Next Falcon 9 on Solid Ground

#123

Post by elchief »

mikeash wrote: post #93
elchief wrote: post #54

What was the % cost reduction in being able to land the boosters again? I read it somewhere a while back but can't find it. It was pretty significant if I recall. TIA.

The first stage accounts for about 75% of the total cost of the Falcon 9, so best case would be a 75% cost reduction. Any refurbishment needed before flying again would reduce that, as well as whatever fixed costs there are for a launch, like fuel, salaries for on-site workers, consumable launch pad equipment, or whatever. Refurbishment is the big wild card. If the rocket is ready to go again with no work then it cou…

Sweet, thx. That's a pretty big game-changer.

Re: SpaceX Plans to Land Next Falcon 9 on Solid Ground

#124

Post by Swannie »

flountown wrote: post #49

Are there any articles or press out there that describe the stabilization tech used on the barge? A lot of the things when looking through Google seem to focus on the challenges of guiding the rocket but not stabilizing the platform. I guess it tends to be a non-issue since it seems their plan all along was landing it on land, but I'd be really interested to see the design story that went into the barge.

My question isn't really about stabilising the platform, as others have mentioned that should be off the shelf marine tech.

But this isn't exactly landing a helicopter on a ship/platform. I'm expecting a rocket to be a fair bit heavier... as that weight comes down, unless it's perfectly on centre, you now have a large force acting to unbalance the platform. Whilst X-Y may be stabilised, the pitch and the yaw is going to be affected by that weight.

Re: SpaceX Plans to Land Next Falcon 9 on Solid Ground

#125

Post by cma »

anigbrowl wrote: post #111
Cshelton wrote: post #8

I think now that they have proven they can 'hit the hole', almost spot on, they'll be able to get approval to go for a try on cleared land space. It sounds like to me, landing on land would be ideal; less expensive and less risk with stabilization and rough waters.

Landing is an awful lot harder than taking off, it seems to me; a single engine rocket with stabilizing jets is a bit like trying to land a pogo stick - possible, but inherently problematic. I know this must seem stupidly obvious, but I wonder if a better design for a reusable launch vehicle isn't 4 engines connected by a frame with the payload in the center, basically a chair. Yeah, it sounds horribly unwieldy with…

I thought quad copters were a special case because of their size and because of the simple and controllable electric power-train that doesn't work so well with gas motors. I would imagine rockets have even more lag, and maybe more narrow thrust-efficiency windows than something like gas motors.

Re: SpaceX Plans to Land Next Falcon 9 on Solid Ground

#126

Post by lutorm »

anigbrowl wrote: post #111
Cshelton wrote: post #8

I think now that they have proven they can 'hit the hole', almost spot on, they'll be able to get approval to go for a try on cleared land space. It sounds like to me, landing on land would be ideal; less expensive and less risk with stabilization and rough waters.

Landing is an awful lot harder than taking off, it seems to me; a single engine rocket with stabilizing jets is a bit like trying to land a pogo stick - possible, but inherently problematic. I know this must seem stupidly obvious, but I wonder if a better design for a reusable launch vehicle isn't 4 engines connected by a frame with the payload in the center, basically a chair. Yeah, it sounds horribly unwieldy with…

I don't think the physics of balancing a rocket on the way down are any different from doing it on the way up.

I'm also not sure where you got the idea that using multiple boosters is a problem. Look up the Atlas 5, Delta IV Heavy, the Space Shuttle, Ariane 5, etc, etc. (And multiple engines on the same booster have been used since the start of the space program.)

Re: SpaceX Plans to Land Next Falcon 9 on Solid Ground

#127

Post by djloche »

jccooper wrote: post #77
0xffff2 wrote: post #17

Earlier quoted context omitted.

Two factors: 1. Yes, they will eventually be launching elsewhere. SpaceX is currently building its own launch facility in Brownsville, TX, which would indeed permit landing at the cape. 2. Elon Musk seems to think that despite the expense, they can fly the rocket back to the launch pad for lighter payloads.

Florida's an awful long way from Brownsville. Take a look at the launch danger zones chart; first stage recovery is just off the coast. Maybe you could finagle a second stage recovery in Florida from Texas, but only from very specific inclinations. Doesn't seem likely to be useful.

My guess is that once they have their facility operational in TX, they will primarily launch from there, and keep Florida and California as backup options for their clients / use when necessary.

Re: SpaceX Plans to Land Next Falcon 9 on Solid Ground

#128

Post by anigbrowl »

lutorm wrote: post #126
anigbrowl wrote: post #111

Earlier quoted context omitted.

Landing is an awful lot harder than taking off, it seems to me; a single engine rocket with stabilizing jets is a bit like trying to land a pogo stick - possible, but inherently problematic. I know this must seem stupidly obvious, but I wonder if a better design for a reusable launch vehicle isn't 4 engines connected by a frame with the payload in the center, basically a chair. Yeah, it sounds horribly unwieldy with…

I don't think the physics of balancing a rocket on the way down are any different from doing it on the way up. I'm also not sure where you got the idea that using multiple boosters is a problem. Look up the Atlas 5, Delta IV Heavy, the Space Shuttle, Ariane 5, etc, etc. (And multiple engines on the same booster have been used since the start of the space program.)

Oh, when I said 'part of a single fuselage' boosters was what I had in mind. Sorry in that wasn't clear.

Re: SpaceX Plans to Land Next Falcon 9 on Solid Ground

#129

Post by cma »

vectorjohn wrote: post #120
harshreality wrote: post #24

Earlier quoted context omitted.

They need to be able to stabilize the rocket's landing in all sorts of conditions if they want to have any hope of landing it on another planet. It's not like interplanetary launches will be able to schedule launches to choose optimal weather conditions for the landing. Maybe, if they're lucky, they'll be able to orbit briefly to avoid bad weather at the landing site, but moderate winds and wind gusts are going to be…

Uh, we've already had a few near landings in non-ideal Earth weather. Mars barely has weather. It has wind, sure, but the air on Mars is about 150 times less dense. I.e., it won't be blowing over any rockets. So basically, landing anywhere on Mars is easy compared to Earth if they just find a flat spot.

That also makes air-braking more challenging. The first stage isn't coming in at orbital velocities, but I'm assuming they are shedding a good amount of velocity using the air?

Re: SpaceX Plans to Land Next Falcon 9 on Solid Ground

#130

Post by Lorento »

anigbrowl wrote: post #111
Cshelton wrote: post #8

I think now that they have proven they can 'hit the hole', almost spot on, they'll be able to get approval to go for a try on cleared land space. It sounds like to me, landing on land would be ideal; less expensive and less risk with stabilization and rough waters.

Landing is an awful lot harder than taking off, it seems to me; a single engine rocket with stabilizing jets is a bit like trying to land a pogo stick - possible, but inherently problematic. I know this must seem stupidly obvious, but I wonder if a better design for a reusable launch vehicle isn't 4 engines connected by a frame with the payload in the center, basically a chair. Yeah, it sounds horribly unwieldy with…

It's always tempting with difficult control problems to imagine why not just do what feels stable? Why not just hold it in place with something? Why not make it shorter and wider? For an example of why not - compare a turtle to a human. The human is inherintely unstable and its vital organs are exposed through weak flesh. If we lose control of our unstable balance, we die when our head hits the ground. The turtle is naturally stable and armor plated! But which one is really best at surviving?
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