[RandallBrown]

When SpaceX launches a rocket, they think it will work. When NASA launches a rocket they know it will work.

The cost of going from "I think this will work" to "I know this will work" is really expensive. It might be cheaper/faster to fail a few times and fix those problems than it would be to verify everything up front.

[elteto]

> When SpaceX launches a rocket, they think it will work. When NASA launches a rocket they know it will work.

That is such an ignorant thing to say. You think Falcon 9 has had 500+ successful launches because they _think_ it will work?

The difference is that SpaceX is a private company that has the ability to iterate fast. NASA is a jobs program and Artemis/SLS a barrel of pork, simple as that.

[emtel]

NASA has killed 19 astronauts. SpaceX: 0

[tavavex]

SpaceX has flown 18 crewed launches on a single type of vehicle, all in the 2020s, all of them either doing an ISS run or an orbital launch. NASA has had over 200 manned launches spanning well over half a century, flown on all sorts of tech, with vastly different designs, kinds of engineering culture, mission profiles. They were the organization that did first-of-its-kind missions. You just bringing up two numbers makes it seem like the companies existed at the same time and were essentially equals, and not like there's a historical innovator that spilled some blood while pushing the limits and a modern private business that made some innovations but is still treading on ground that's so well-known because of all the experience and knowledge we already gathered from those past risky ventures.

[emtel]

I’m simply refuting the claim that when nasa launches a mission, they “know it will work”. They certainly do not.

[freejazz]

Again, that is put so vaguely as to be actionably useless.

[RandallBrown]

So let's say you want to check something like a new fuel nozzle.

SpaceX might design and build the nozzle, then put it in the rocket and launch it. It might work how they intended, or it might not, but they'll find out immediately. They'll make changes, build a new nozzle, launch another rocket, and continue until it works like they want.

NASA will do a lot more testing, simulation, redesigning, etc. until they KNOW that the nozzle will perform perfectly on the first try.

On the surface, NASA's approach sounds cheaper because you aren't wasting rockets. In reality it looks like SpaceX's approach might be better.

[elteto]

You don't test the nozzle on _launch day_, what kind of ridiculous statement is that? You think the Air Force is paying SpaceX so they can test things the day it flies?

All components go through several test campaigns on the ground, while iterating on the design to address issues. These campaigns take months/years. That's why changes are stacked into "blocks", which are the equivalent of rocket versions. Each block must be certified by the Air Force and NASA to be deemed worthy of flying their payloads.

[ggreer]

A couple days before COTS-1[1] was to launch, a crack was discovered in the second stage nozzle. Rather than wait a month to fabricate and install a new one, SpaceX had a guy climb inside the rocket and use some shears to cut off the lower third of the nozzle. The rocket launched without issue.[2]

So while you're right that SpaceX doesn't typically do this sort of thing, NASA did pay them to fly an untested nozzle design.

1. https://en.wikipedia.org/wiki/SpaceX_COTS_Demo_Flight_1

2. See the section titled "Snipping the nozzle" at https://arstechnica.com/science/2020/06/forget-dragon-the-fa...

[elteto]

It was a demo mission and that change was actually consulted and approved by NASA.

[RandallBrown]

I think you're purposefully missing my point.

[ThrowawayTestr]

SpaceX is willing to blow up a rocket, even if it exploding is fully planned and expected. That's it, really not hard to comprehend.

[kakapo5672]

Columbia. Challenger.