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Space Discussion Thread

Benm

Benm

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It would not really matter what propulsion system you use for launching people 'cannon style' into space: It could be EM but just as well be powered by compressed gas or even some pulley/belt system that runs along the length.

Building something like that will be a monumental task, but then again, so was building the LHC at CERN, and that worked out well :)
 





paul1598419

paul1598419

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IDK, Alex. it didn't work with the space shuttles. They had to be literally rebuilt every time it was going to be used again.
 
paul1598419

paul1598419

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IIRC, Ronny and NASA hid the fact that it cost $1 billion to get a shuttle ready to launch. And that was 1980s money. The shuttle was a poor design and was expensive to use. And back then they used them a lot.
 
Benm

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Maybe, but the shuttle was also largely a prestige project. Russia built some prototypes of a similar approach but abandoned this method of launch - perhaps because it was not cost effective after all.

SpaceX might believe it will actually be cost effective to re-use launch vehicles. I can't say if it is or is not, this depends on how much cheaper it is to refurbish and refuel a used one compared to building an brand new one, and how much heavier it has to be to be re-usable.

That is does have be significantly heavier seems quite evident when they land them ass down - all the fuel burned in that procedure could have been payload in the second stage.

Even if the fuel required to land the first stage is only a percent of the total fuel that would be a huge disadvantage. With spaceflight as it currently is, the vast majority of fuel is used to actually lift more fuel, not final payload, to higher and higher altitudes.

One big difference between NASA and SpaceX at this moment is that the latter do not carry people into space. This is very significant since you cannot really factor in the cost of loss of life, while you can factor in (and insure) the cost of losing payload (like a sat).

The latter is not uncommon, insurance premiums are in the order of 5 to 15% of the cost of the payload, depending on what system is used. So launching say a billion dollar payload could cost you an extra 100 million if you use a less reliable launch system unless you launch many and can factor in the occasional loss (for example when deploying something like a GNS or satphone constellaton).
 
diachi

diachi

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paul1598419 said:
IDK, Alex. it didn't work with the space shuttles. They had to be literally rebuilt every time it was going to be used again.
Click to expand...

Entirely different beast, both boosters and the fuel tank had to be replaced on the shuttle after a launch, as well as extensive refurbishment to the shuttle itself.

We don't know exactly what SpaceX did to refurbish this rocket but we know it's using the same 9 engines and the same tanks/structure, with some fresh paint. We also know that the launch cost for this reused core is cheaper than for a new rocket, at present IIRC it's 10% cheaper than a launch with a new core (which saves about $6,000,000). They are expecting final cost reductions to be on the order of 30% for a flight proven booster. Other landed cores have been through multiple full duration test burns on the ground, things are looking good.

This one took 4 months to inspect and refurbish, but it's not the final version and they're still learning how to do this.

This current version of the Falcon 9 is only supposed to be able to re-fly 2-3 times. With the Block V they are aiming for 10 launches on a single core IIRC, it'll also be even easier to refurbish after a landing than the current Block III.

This is all very encouraging.
 
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Benm

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I guess time will tell, eventually.

I wish them best of luck, but it could be such that those refurbished systems are just more accident prone for whatever reason, it will take a large number of launches to get a reliable figure for that.

There could be other considerations though, perhaps they will use the refurbished units for less valuable payloads only making it an attractive option to get something into orbit, as long as it is not very valuable or easily replaced.

Some payloads fall into that market, such as common sats for communication that are, relatively, 'mass produced' and the extra cost of building 50 instead of 40 is not that great since most of the cost is in R&D.

Then again, if I was the payload, please use the brand new one, i'll pay extra ;)
 
paul1598419

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The $1 billion cost I was referring to was just for the shuttle alone and didn't include the rocket or stages to it or fuel. It cost that much just to get the shuttle ready for relaunch and was in 1980s money.
 
Benm

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I understand, but the shuttle was never really a feasible system to get payloads into orbit at a reasonable price. It was used to deploy some US payloads, but all private, commercial, payloads were going up from russia at that time.

SpaceX is a commerical company that, i suppose, wants to offer transfer into orbit at a competitive price and acceptable risk of loss.

I cannot say if they will succeed in that or not based on a single re-use of a vehicle. The future track record will tell that story, and if they keep up the work we'll all see the data.

Another thing is that the space shuttle was intended to carry people which reduces the acceptable risk of catastrophic failure to zero.

This demand was not met with one exploding on launch and another breaking up on re-entry. With a 130 or so launches resulting in 2 deadly events claiming 7 lives each the platform proved unsuitable for human transport and was binned. As for cargo transport these figures are very good though, possible the best in the industry, although the things were to expensive to launch anything but the most valuable payloads.
 
paul1598419

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No there weren't. The US and NASA took commercial payloads in the 1980s and deployed them in orbit, and did so at a discounted rate. There were times in the 1980s when there were as many as two launches a month. I was well into my thirties then and remember it well.
 
diachi

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Benm said:
I understand, but the shuttle was never really a feasible system to get payloads into orbit at a reasonable price. It was used to deploy some US payloads, but all private, commercial, payloads were going up from russia at that time.

SpaceX is a commerical company that, i suppose, wants to offer transfer into orbit at a competitive price and acceptable risk of loss.

I cannot say if they will succeed in that or not based on a single re-use of a vehicle. The future track record will tell that story, and if they keep up the work we'll all see the data.

Another thing is that the space shuttle was intended to carry people which reduces the acceptable risk of catastrophic failure to zero.

This demand was not met with one exploding on launch and another breaking up on re-entry. With a 130 or so launches resulting in 2 deadly events claiming 7 lives each the platform proved unsuitable for human transport and was binned. As for cargo transport these figures are very good though, possible the best in the industry, although the things were to expensive to launch anything but the most valuable payloads.
Click to expand...


The goal for SpaceX I believe is a price reduction of ~30% on launch cost, which when a launch costs ~$65,000,000, that's a big saving. We know SES-10 received a discount, although we don't know exactly how much. We also know they didn't see any noteworthy increase in launch insurance costs.

Doing some more reading for a refresher, their goal for re-flights per core is 10 launches without refurbishment, i.e. very few, if any, parts being replaced. With refurbishment they are aiming for 100 launches per core. At present pad turnaround is ~2 weeks it seems, perhaps a little less, as long as the range isn't in use by another launch at least. So as long as they have a rocket ready and the range is free, they can launch every two weeks. The turnaround goal is 24 hours.

Fuel costs are a tiny fraction of the total launch cost, high estimates are $300,000 or about 0.5% of the total launch cost ($62M).

Falcon 9 Block 5 and Dragon 2 are being designed to carry crew, Falcon Heavy will be used to send people on a free return orbit around the moon. So Falcon 9/Heavy are intended to be man rated eventually, they are just working their way towards it. The first crewed launch is scheduled for May of next year.

Shuttle reliability, even for Cargo missions, is not the best in the industry, certainly not if you're accounting for cost too. Atlas V for example has a perfect mission success rate, with all 70 launches achieving their mission goal, one or two suffered anomalies but still completed the mission.

Soyuz has over 900 successful missions, with an overall success rate of 97.5%, 1% lower than that of the shuttle, but it's also far cheaper.

Maybe it won't work out for SpaceX, but so far things are looking encouraging. At the very least, they're creating some competition and showing that these things can actually be done.
 
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Benm

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The competition surely is a good thing, it keeps the other players sharp and also sets a more realistic price point.

As for fuel cost i'd rather say rebuilding cost. The actual fuel may not be that expensive, but loading it up for a reliable launch is another matter - it's not like putting fuel in an airplane.

For manned missions we shall see: it also depends on what is the acceptable risk for getting killed in attempting it. In hindsight the risk of death on a space shutte return flight was well over 1%, i'm not sure that figure would still be considered acceptable today.

Consider this: on an average day there are in the order of 50.000 flights with large (737/A320 or bigger) scheduled flights globally. A failure rate of 1% would mean there would be 500 major air crashes every single day around the world - doesn't sound like a good service/product to me.
 
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