Space-X: what am I missing??

I'm sure this will be a lightning rod of a post, but can someone explain why the approach of the SpaceX team with falcon makes sense? The argument I understand is that significant costs can be saved if we don't modify the aeronautics of a reusable vehicle- IOW, vertical take off is best suited by vertical landing.

Where I'm stuck is the fact that the vehicle needs to carry/reserve fuel for the landing. How is that more economical than supplying enough of the good stuff to get the job done, and then having to save some we can return vertical?

Others will supply more complete answers, but...

1. Fuel is cheap.
2. The empty booster is relatively light.

I've replied to you in the SpaceX Falcon 9 Historic Landing Thread:

https://www.rocketryforum.com/showt...p-most-recent-missions)&p=1671842#post1671842

I think it would be best to take further discussion there since what you bring up is at the heart of doing the landings to begin with.

There will always be different fuel requirements for different missions based on payload and required orbit. Fuel loading will vary from flight to flight according to that requirement. They can't have a different size rocket for each of the different fuel loads, so sometimes the is space available on that stage to be able to add fuel for the required flyback, and the mass penalty is acceptable. It's not like they have to make room for it. If the flight is one of the faster GTO flights then the barge landings are the only option because of the fuel load usually required for the high orbits.

I guess it is conceivable to have a payload that requires all the available fuel space and mass penalty as to not be able to land the first stage. That has not been seen since they have been doing the landings as they are currently.

As someone said, the stage is remarkably light with the other stages detached and most of the fuel burned. That is one of the big factors in the reuseability equation.

Its really cool to watch them pull off a landing but it does seem like a lot of extra engineering to do so. Hummm, if I put a second smaller motor tube in my rockets maybe I can remove the parachute and land vertically? Ahhhhh, probably not.

As Musk has said, the booster costs 10's of millions of dollars, the fuel to fly it to space only about $100,000. Even with the costs of the barge, storage, refurbishment, etc., much cheaper to spend a few millions dollars to be able to reuse a booster than to build a new one each time. *Should* allow them to fly far more often and for less money than other space vendors.

I like his example of airplanes. Air travel would never have become common place if each airplane was only used once.


Tony

It's not just a metal cylinder with fuel in it and some fins. If it were then the fuel would be the most costly part of the rocket. In our HPRs an H or I motor is very much a significant portion of the cost of each rocket, but in the Falcon 9 the fuel is a tiny fraction.

The 9 Merlin engines, the rocket body, all the controls, etc. all cost much much much more than the fuel. So if adding a little fuel and the space for it can get all that expensive stuff back in a condition that it can be reused, it's very much worth it.

Then too, there's the reduced R&D costs and shortened improvement cycles from having retrieved units to study.

soopirV said:

I'm sure this will be a lightning rod of a post, but can someone explain why the approach of the SpaceX team with falcon makes sense? The argument I understand is that significant costs can be saved if we don't modify the aeronautics of a reusable vehicle- IOW, vertical take off is best suited by vertical landing.

Where I'm stuck is the fact that the vehicle needs to carry/reserve fuel for the landing. How is that more economical than supplying enough of the good stuff to get the job done, and then having to save some we can return vertical?

Click to expand...

Everything above mentions a lot of savings.
The sheer cost of softlanding in the ocean: chutes, deployment hdw, etc.
But the barge equipment to find, lift, load and carry back to another unloading / loading equipment system to take it to a refurbishing facility, the decontamination of the salty sea water is a huge cost alone.

Mushtang said:

It's not just a metal cylinder with fuel in it and some fins. If it were then the fuel would be the most costly part of the rocket. In our HPRs an H or I motor is very much a significant portion of the cost of each rocket, but in the Falcon 9 the fuel is a tiny fraction.

The 9 Merlin engines, the rocket body, all the controls, etc. all cost much much much more than the fuel. So if adding a little fuel and the space for it can get all that expensive stuff back in a condition that it can be reused, it's very much worth it.

Click to expand...

Good point! Turnaround by having reconditioned motors, controls, etc, then turn around is even faster. The old equipment goes to a rebuilding facility for a flight down the road.

Dave A said:

Everything above mentions a lot of savings.
The sheer cost of softlanding in the ocean: chutes, deployment hdw, etc.
But the barge equipment to find, lift, load and carry back to another unloading / loading equipment system to take it to a refurbishing facility, the decontamination of the salty sea water is a huge cost alone.

Click to expand...

Pales in comparison to the cost and time to build a new booster from scratch. Most estimates peg the cost of the first stage at about $30 million. Even reusing a few boosters more than pays for all the additional infrastructure.


Tony

and cost of chutes? what chutes?

As I said earlier, I've replied to this, with a lot of info, in the SpaceX Falcon-9 Historic Landing thread.

Check it out if you have not already.

https://www.rocketryforum.com/showt...p-most-recent-missions)&p=1671842#post1671842

Dave A said:

Everything above mentions a lot of savings.
The sheer cost of softlanding in the ocean: chutes, deployment hdw, etc.
But the barge equipment to find, lift, load and carry back to another unloading / loading equipment system to take it to a refurbishing facility, the decontamination of the salty sea water is a huge cost alone.

Click to expand...

See my reply to this in the Landing Thread:

https://www.rocketryforum.com/showt...p-most-recent-missions)&p=1671938#post1671938

Dave A said:

Everything above mentions a lot of savings.
The sheer cost of softlanding in the ocean: chutes, deployment hdw, etc.
But the barge equipment to find, lift, load and carry back to another unloading / loading equipment system to take it to a refurbishing facility, the decontamination of the salty sea water is a huge cost alone.

Click to expand...

Like the Shuttle boosters used to be recovered? You're totally right. I find it hard to believe that recovering those saved any money, with all the recovery and refurbishing costs that was needed as you mentioned. Those boosters didn't have an engine since they were solid fuel, so I wonder what percentage the booster casing vs filled booster would be?

But with the Falcon 9 booster there's so much more that gets recovered, without smashing into the water hard and being contaminated with salt water.

Mushtang said:

Like the Shuttle boosters used to be recovered? You're totally right. I find it hard to believe that recovering those saved any money, with all the recovery and refurbishing costs that was needed as you mentioned. Those boosters didn't have an engine since they were solid fuel, so I wonder what percentage the booster casing vs filled booster would be?

But with the Falcon 9 booster there's so much more that gets recovered, without smashing into the water hard and being contaminated with salt water.

Click to expand...

I've read that it cost 2.5 - 3 times as much to refurbish than to initially make, but maybe the example set by reusing them was worth more than the cost.

Incongruent said:

I've read that it cost 2.5 - 3 times as much to refurbish than to initially make, but maybe the example set by reusing them was worth more than the cost.

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As I understand it, the only benefit was political. One of the important senators on the finance committee was from the district where the SRB's were refurbished, or some such thing. It was always about the money.

Incongruent said:

I've read that it cost 2.5 - 3 times as much to refurbish than to initially make, but maybe the example set by reusing them was worth more than the cost.

Click to expand...

If that's true then we need to put a stop to this!! Oh. Right.

Then too, there's the reduced R&D costs and shortened improvement cycles from having retrieved units to study.

Click to expand...

Don't underestimate the worth of this ability to examine flight units. Destructive testing and extensive examination of the flown units will be providing priceless data that enables SpaceX to improve their reliability, probably by orders of magnitude. This will really pay dividends for them when the launch cadence ramps up, and especially when starting the manned missions. Insurance costs are likely to come down too.

There was a bit of a delay in flights after the retrieval of the first booster IIRC. I am almost willing to bet something was found during the inspection that resulted in some necessary corrective action on future flights.

Many other rockets have flown successfully, but how many of them have actually studied flight motors, rather than just ones that have been tested on a static stand? Not a large amount I would think.

Mushtang said:

Like the Shuttle boosters used to be recovered? You're totally right. I find it hard to believe that recovering those saved any money, with all the recovery and refurbishing costs that was needed as you mentioned. Those boosters didn't have an engine since they were solid fuel, so I wonder what percentage the booster casing vs filled booster would be?

But with the Falcon 9 booster there's so much more that gets recovered, without smashing into the water hard and being contaminated with salt water.

Click to expand...

This really is the crux of my question- we "recovered" reusable pieces from the Shuttle Orbiter for decades without the need for them to land themselves on a barge. I guess the environmental stress is eliminated if you can completely control the recovery area (not salt water, no impact damage)...

soopirV said:

This really is the crux of my question- we "recovered" reusable pieces from the Shuttle Orbiter for decades without the need for them to land themselves on a barge. I guess the environmental stress is eliminated if you can completely control the recovery area (not salt water, no impact damage)...

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I"ll read Peartree's post now...just wanted to get this clarification out there...it's not that I thought these things should be disposable.

With a bit of levity :wink:, I can think of three reasons:

1. Because having your rocket reach space and then land itself is a requirement for a level 6 certification.

2. Because it's cool.

3. Don't you reuse your rockets after refueling?

Cabernut said:

With a bit of levity :wink:, I can think of three reasons:

1. Because having your rocket reach space and then land itself is a requirement for a level 6 certification.

2. Because it's cool.

3. Don't you reuse your rockets after refueling?

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Touché! My launch/recovery ratio is better than Kim Jong un's, but not by a lot...