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Comment by armada651 | Hacker News Reader

The thing is the launch likely failed for reasons that were known beforehand and were noticable even to a layman.

They purposefully chose not to have a flame diverter, instead they were hoping to get away with simply blowing up the launchpad beneath them. I respect that they're trying to push boundaries, but this just seems foolish.

For a company so focused on reducing cost through reusability, why did they choose to blow up the launch pad upon launch? I understand building a flame diverter for a rocket this massive is an incredible amount of work, but if it makes subsequent launches cheaper then wouldn't that amortize the costs?

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Elon wrote: https://twitter.com/elonmusk/status/1649523985837686784

> 3 months ago, we started building a massive water-cooled, steel plate to go under the launch mount.

> Wasn’t ready in time & we wrongly thought, based on static fire data, that Fondag would make it through 1 launch.

To me, it sounds like people that would have been considered experts (and probably still are) made assessments than turned out to be incorrect.

Some times you just have to try. This was way bigger than anything that's gone before. I'm sure they'll have plenty of data now to make the launch pad even better than it would otherwise have been.

Videos of the debris storm were pretty mind boggling to watch - it's difficult to comprehend the sheer amount of energy expended.

I am truly looking forward to the learnings published from this.

Where is your evidence for "they were hoping to get away with simply blowing up the launchpad"?

"Aspiring to have no flame diverter in Boca, but this could turn out to be a mistake" -Musk https://twitter.com/elonmusk/status/1313952039869788173

Because they chose to go ahead with the launch with no flame diverter or anything else that would've protected the launch pad?

I think that's a reasonable response.

At the same time, if it would have taken several more months to install a flame diverter / metal plating below the launch pad, would that be worth it, or negate the progress made by gathering flight data? I'm not sure we can know that for sure.

I would hazard a guess that in the long term, it will have been the right decision.

keep in mind this is still a prototype rocket, they have no guarantee that they won't learn anything important about how this should look like or what issues it could introduce

they used something they knew to work so there is one less variable that should prevent liftoff

at this point there is no reducing the cost phase yet, they try to test assumptions and learn what and how things can go wrong. It's much better that things go wrong at test flight than at mission flight.

if they would get lucky and none of the issues would manifest, they could assume that design is perfect and do not try to improve it. so it's good if whatever can go wrong goes wrong at test flight

> if they would get lucky and none of the issues would manifest, they could assume that design is perfect and do not try to improve it. so it's good if whatever can go wrong goes wrong at test flight

I agree that the success should be measured in lessons learned from the launch. However we learned next to nothing about the second stage because the first stage failed for reasons that weren't unexpected.

So from that perspective the launch could be considered a failure, because they traded getting data on the second stage for learning a lesson that was already known.

assuming that this failure was caused by failed engines, I think this is a very important lesson, engines can fail during real missing and if their algorithms couldn't account correctly that, this is a very important thing to improve.

and remember, as you already mentioned, that stage 2 won't even start until stage 1 succeeds, so they need to perfect that first.

but I see your point, if they would manage to separate before stage 1 failure they could gather more data

Engines are not supposed to fail ever. Super Heavy does not have sufficient margin to handle multiple failures (maybe one, maybe), and Starship has the same engines, where one failing means it is liable to just fall from the sky.

Unless on the Moon, but then it would have to LEO or lunar orbit abort if it does not burn up on the spot and require a recovery mission.

It is also indicative of how their lunar starship will damage itself on descent. At least NASA came to it's senses and funded a backup plan.

It is not indicative of that.

Lunar Starship is the second stage, this was the first that did the damage. Even that is different from the one launched in the recent test; it’s a variant that will do the final landing on different engines high up on the rocket. Per Wikipedia:

> Within 100 meters of the lunar surface, the variant will utilize high‑thrust RCS thrusters located mid‑body to avoid plume impingement problems with the lunar regolith.

Landing is also very different than takeoff; the F9 takes off with nine, lands with one. Likewise, Super Heavy launches with 33, but Starship lands with 3-6, and three of those are the vacuum variant, with much less focused plumes.

> but lands with 3-6, and three of those are the vacuum variant

First stage will likely use more than 3-6, none will be the vacuum variant.

The first stage isn’t going anywhere near lunar regolith. Ever.

And second stage has different engines since when? Starship proper is not that different, it has fewer engines, its landing gear provides worse conditions than the launchpad.

Second stage (Starship) has always had different engines (both in quantity and construction; some are vacuum Raptors) than Super Heavy. Lunar Starship is itself a variant of the regular second stage; it'll need the cargo elevator, for example, which is shown in NASA's announcement graphics.

https://www.youtube.com/watch?v=KEnz8V97Qck&t=2100

> for the terminal descent of Starship, a few tens of meters before we touch down on the lunar surface, we actually use a high-thrust RCS system, so that we don't impinge on the surface of the Moon with the high-thrust Raptor engines. ... uses the same methane and oxygen propellants as Raptor.

(We'll see if that winds up being the actual final solution, but they've clearly at least thought about this aspect.)

You were talking about F9 landing, and taking off with 33 engines. Only the first stage lands on the F9. Only the first stage has 33 engines. I guess it's more confusing when Starship is what the whole ship is called, and possibly the second stage.

Falcon 9 is a specific clear example of landing != takeoff.

Starship != Super Heavy

Lunar Starship != Starship

Earth != Moon

All of these differences combined make the test not the slightest bit indicative of how things would work for a lunar Starship landing.

> Landing is also very different than takeoff;

Lunar Starship is going to use the same engines for takeoff, assuming they don't get smashed by flying debris.

Much fewer, half of them are vacuum variants (much less focused plume), and lunar gravity is much lower, meaning dramatically lower thrust required to get off the ground.

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