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SpaceX’s monstrous, dirt-cheap Starship may transform space travel

economist.com

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Re: SpaceX’s monstrous, dirt-cheap Starship may transform space travel

#31

Post by jacobkranz »

tablespoon wrote: post #18
geocrasher wrote: post #14

The thing that's impressive to me, in addition to the sheer size of these machines, is the engines . The Raptor 2 is groundbreaking. And there's 30+ of them between both stages. It's just incredible, and there's nothing like it that's been done.

> The thing that's impressive to me, in addition to the sheer size of these machines, is the engines. The Raptor 2 is groundbreaking. And there's 30+ of them between both stages. It's just incredible, and there's nothing like it that's been done. I may be wrong, but isn't the reason there are so many engines on their rockets is because SpaceX isn't good at building big rocket engines?

My understanding was that if one goes out then they still have 32 left

Re: SpaceX’s monstrous, dirt-cheap Starship may transform space travel

#32

Post by karmicthreat »

tablespoon wrote: post #18
geocrasher wrote: post #14

The thing that's impressive to me, in addition to the sheer size of these machines, is the engines . The Raptor 2 is groundbreaking. And there's 30+ of them between both stages. It's just incredible, and there's nothing like it that's been done.

> The thing that's impressive to me, in addition to the sheer size of these machines, is the engines. The Raptor 2 is groundbreaking. And there's 30+ of them between both stages. It's just incredible, and there's nothing like it that's been done. I may be wrong, but isn't the reason there are so many engines on their rockets is because SpaceX isn't good at building big rocket engines?

I don't think they have even attempted to build a large engine. But SpaceX is setup like an assembly line rather than some bespoke engine maker. A larger engine would require larger tooling, 3d printers, etc. Also with 30+ engines its less of an investment if one goes bad, just swap it out.

They always have the option of designing another larger engine later.

Re: SpaceX’s monstrous, dirt-cheap Starship may transform space travel

#33

Post by IshKebab »

tablespoon wrote: post #18
geocrasher wrote: post #14

The thing that's impressive to me, in addition to the sheer size of these machines, is the engines . The Raptor 2 is groundbreaking. And there's 30+ of them between both stages. It's just incredible, and there's nothing like it that's been done.

> The thing that's impressive to me, in addition to the sheer size of these machines, is the engines. The Raptor 2 is groundbreaking. And there's 30+ of them between both stages. It's just incredible, and there's nothing like it that's been done. I may be wrong, but isn't the reason there are so many engines on their rockets is because SpaceX isn't good at building big rocket engines?

No. There are other good reasons to use lots of small engines. Redundancy. Ability to throttle down (very important for Starship). You can use the same engines on both stages. Easier to gimbal.

Re: SpaceX’s monstrous, dirt-cheap Starship may transform space travel

#35

Post by ebruchez »

CamperBob2 wrote: post #13
tjchear wrote: post #12

Earlier quoted context omitted.

For lack of a political will or the technical know how?

The popular wisdom is that we literally lost some of the technical specs and drawings. A lot of the R&D would have to be redone from scratch... not that it wouldn't make sense to do that anyway, 50+ years later.

The CuriousMarc YouTube channel [1] features a current series where they work on some Saturn transmission equipment (Apollo Comms). They also also restored an AGC (Apollo Guidance Computer). Those were incredible designs for the time, but you wouldn't build (and probably couldn't even if you tried) these modules this way today.

I'd say the loss is more one of history than actual utility. The only way would have been to keep the Saturn V going during the whole time, and upgrade its technology as time went.

[1] https://www.youtube.com/c/CuriousMarc

Re: SpaceX’s monstrous, dirt-cheap Starship may transform space travel

#36

Post by mlindner »

tablespoon wrote: post #18
geocrasher wrote: post #14

The thing that's impressive to me, in addition to the sheer size of these machines, is the engines . The Raptor 2 is groundbreaking. And there's 30+ of them between both stages. It's just incredible, and there's nothing like it that's been done.

> The thing that's impressive to me, in addition to the sheer size of these machines, is the engines. The Raptor 2 is groundbreaking. And there's 30+ of them between both stages. It's just incredible, and there's nothing like it that's been done. I may be wrong, but isn't the reason there are so many engines on their rockets is because SpaceX isn't good at building big rocket engines?

Many smaller engines is cheaper than one big one as you can streamline manufacturing. Also large engines develop combustion instability much easier. They're also harder to cool because of the square-cube law (more heat, less surface area).

It also gives you engine out capability and also the ability to effectively throttle the rocket in a much more fine grained way by shutting off engines.

Re: SpaceX’s monstrous, dirt-cheap Starship may transform space travel

#37

Post by MPSimmons »

tjchear wrote: post #12
CamperBob2 wrote: post #10

Earlier quoted context omitted.

I found it depressing. Ships aren't built to stay in the harbor, and rockets aren't built to lie on their side rusting. They say we couldn't build another Saturn V if we tried. Apparently that old saw is true enough, at least for the original contractors.

For lack of a political will or the technical know how?

In order to make a vehicle like that, you need the tools to make it. That doesn't just include wrenches and hammers - it includes the tooling used to form the curve of the skin and the area you assemble the pieces into. Almost all of that is gone, disassembled or misplaced.

Re: SpaceX’s monstrous, dirt-cheap Starship may transform space travel

#38

Post by jiggawatts »

CamperBob2 wrote: post #10
kilroy123 wrote: post #6

If you're ever in the Houston area, I highly recommend going to see NASA Johnson Space Center. They have a full-size replica (?) Saturn V rocket on its side, you can see. You simply can't grasp how big these rockets are until you see it up close. It's like a tall building blasting off into space. They're humongous. I hope to one day see Starship up close in person as it takes off to space.

I found it depressing. Ships aren't built to stay in the harbor, and rockets aren't built to lie on their side rusting. They say we couldn't build another Saturn V if we tried. Apparently that old saw is true enough, at least for the original contractors.

The design is now thoroughly outdated. It wouldn't be cost-effective to reproduce a Saturn V as-is.

The equivalent rocket is the Starship, which clearly can be built.

Technologies like 3D printing, new alloys, better fuels, modern computers, etc... have made dramatic differences to the design and construction of these rockets.

Have a look at the circuitry used on the Saturn V: http://www.righto.com/2020/04/a-circuit-board-from-saturn-v-...

Especially the "instrument unit": http://static.righto.com/images/lvda/IU-labeled.jpg

It's huuuuuuge! The computer power of that entire thing could fit into a single chip these days. Trying to reproduce something like that 1:1 in the modern age would be just absurd.

Note that the Saturn V design isn't just cost-inefficient because technology has moved on. It wasn't cost effective back then either! The per-launch costs were over $1B in inflation adjusted dollars, putting it squarely into the same ballpark has the SLS, which is a monstrously expensive pork-barrel project designed primarily to burn money, not rocket fuel.

Re: SpaceX’s monstrous, dirt-cheap Starship may transform space travel

#39

Post by arcticbull »

Remember folks Elon has a way of, er, overstating. He promised that SpaceX launches cost what, 1% of current launches? So far, they're more expensive than the Space Shuttle it replaced in NASA contracts. Their own numbers say that in the fullness of time they may be 10% cheaper. So far, not so.

Space exploration is great, we should do it, and this rocket sounds cool. We should do it even if it is expensive.

But "dirt cheap" is probably an Elon-ism, closer to "full self driving by 2018."

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