SpaceX Starship development: fifth flight, captures booster

[Rive]

starship seems to me to be the second only attempt in history to make a functioning rocket out of so many parallel engines

Just for the log: Falcon Heavy has 27 engines.

 

[artis]

Just for the log: Falcon Heavy has 27 engines.

Ok I missed that , haven't followed that closely to latest advancements in rocket engineering.
So Soviet N1, Space x's Falcon and starship , are there any others?

 

[gleem]

Don't wish to sound like mr. Wise guy or mr. "told ya so" but rockets with far less thrust and less engine exhaust require water spray jets to save the launchpad so that it can be reused without repairs. NASA knows this, everyone knows this, it's been practically tested.

They intend to use a steel water jacketed plate to dissipate the heat. The engines generate over 90 GW of heat. I would suppose you don't want to generate steam in the jacket. Steel is a poor conductor of heat. This plate is about 10m in diameter. Even if say 10% of the heat is transferred to the jacket you need to absorb 9GW for about 3 seconds. The water in the plate will be in there for several seconds at least for a surface temperature of several thousand degrees C. If bubbles form at the surface of the plate will the plate buckle or melt?

Musk always talks about using the simplest solution with minimum parts. A water deluge/flame trench system seems like the best KISS solution.

And then there is no sound abatement.

Good Luck.

 

[russ_watters]

Don't wish to sound like mr. Wise guy or mr. "told ya so" but rockets with far less thrust and less engine exhaust require water spray jets to save the launchpad so that it can be reused without repairs. NASA knows this, everyone knows this, it's been practically tested.

How in the world anyone at SpaceX thought that this rocket would not absolutely obliterate everything below it especially without a waterjet or whatever flame retarder , I just don't get it.

I would understand the wish to rush forward without delays and then repair whatever damage comes afterward but thinking such a launch wouldn't cause serious damage is simply not imaginable.

I don't like the apparent shoot-from-the-hip approach either, but presumably NASA did review and approve the pad design/construction prior to launch.

 

[russ_watters]

Musk always talks about using the simplest solution with minimum parts. A water deluge/flame trench system seems like the best KISS solution.

And then there is no sound abatement.

I'd been under the impression that the water deluge was more/exclusively for sound abatement. Maybe they calculated they didn't need it.

 

[gleem]

Cape Canaveral is next to Merritt Island national wildlife refuge so sound abatement would be desirable not to affect the wildlife greatly.

Starbase at Boca Chica TX is 1 mile from the Las Palomos wildlife management area and 2 miles from the Boca Chica wildlife refuge. With a water deluge system, the Saturn V generates a sound level of 145 dB (pain threshold for humans) at two miles. Spectators are kept more than 5 miles from the launch pad. Why noise abatement conditions have not been imposed seems strange.

With no noise abatement and twice the power, the noise levels will be higher.

Maybe they calculated they didn't need it.

Do you think they would do it for a few birds and turtles?

 

[artis]

@gleem I did not know that the total heat output of those engines was 90GW, but i can't find any reference for that either , can you please post some?

Either way Elon's remarks about a "steel plate" do sound somewhat humorous.

From what I understand the waterjet is there not so much for sound dampening but for the rapid cooling of the exhaust flame/gas so that it doesn't behave like a welding plasma torch vaporizing and cutting everything in it's path.
Take a propane oxygen gas torch cutter and then introduce a water spray to traverse the flame and you should get it to stop being effective at cutting.

At least that's how I always understood it, a cooling mechanism to save the foundation structures and lessen the escaping flame damage and velocity.

 

[russ_watters]

With no noise abatement and twice the power, the noise levels will be higher....

Do you think they would do it for a few birds and turtles?

By "sound" I thought we really meant "vibration". Harmful to the spacecraft.

https://en.m.wikipedia.org/wiki/Sound_suppression_system

 

[gleem]

@gleem I did not know that the total heat output of those engines was 90GW, but i can't find any reference for that either , can you please post some?

I got 120 MHp from somewhere on the web for the total HP of the Starship which I can't remember and converted it to watts. However, I can show a direct calculation using space X fuel consumption of 194kg/sec/engine which gives a higher heat output.

1 mole CH4 produces 890.4 Kj of heat.
There are 22.7 moles in a kg of CH4
The engine uses 194kg/sec × 22.7moles/kg ×890.4 Kj/mole =3.92 x10⁹ j/sec
With 33 engines a total heat production of 129.4 Gw.

but not all that heat is transferred to the earth.

From what I understand the waterjet is there not so much for sound dampening but for the rapid cooling of the exhaust flame/gas so that it doesn't behave like a welding plasma torch vaporizing and cutting everything in it's path.

from https://en.wikipedia.org/wiki/Sound_suppression_system

Sites for launching large rockets are often equipped with a sound suppression system to absorb or deflect acoustic energy generated during a rocket launch. As engine exhaust gasses exceed the speed of sound, they collide with the ambient air and shockwaves are created, with noise levels approaching 200 db.

By "sound" I thought we really meant "vibration". Harmful to the spacecraft.

That is the biggest concern I am sure but 145 dB at two miles with a water deluge is very "loud" and the Starship test broke windows in Port Isabel 6 miles away.

 

[mfb]

How in the world anyone at SpaceX thought that this rocket would not absolutely obliterate everything below it especially without a waterjet or whatever flame retarder , I just don't get it.

SpaceX has taken risks with test articles frequently - often it works (despite "everyone" claiming it cannot work in advance) and ends up being a great solution. In the rare cases where it doesn't work everyone has to shout how SpaceX is stupid, of course.

It's likely the launch pad would have survived quite well if the launch wouldn't have crushed the soil beneath the concrete plate. Well enough for a test flight - the long-term solution was already in production but not ready yet.

Water reduces the sound level somewhat, but there is no indication that sound levels were a problem for the launch. Same as for the plate, will be available for future launches, but wasn't seen as necessary for the first launch (rightfully in this case). Saturn V didn't use a sound suppression system by the way. There are a couple of others that don't have one, too.

Interestingly, a flame trench increases sound levels in most places. The engine exhaust accumulating below the rocket without one leads to some cancellation.

Starship can do its mission even if three engines are out throughout the whole flight. Losing more engines later can be acceptable, it depends on the details which engines stop when. A large number of engines leads to more redundancy. Long-term we'll likely see engine failure rates of the order of 0.1%, typical for established engines. If you have 5 engines then you need all 5, that gives you a 0.5% risk to lose the rocket. The risk to lose 4 or more engines out of 33 is just 1 in 25 million.

Either way Elon's remarks about a "steel plate" do sound somewhat humorous.

We have pictures of the steel plate they are building. The components were already spotted before the Starship test launch.

 

[Rive]

SpaceX has taken risks with test articles frequently

So often that I can't help to suspect that they are cutting cost on disassembly and disposal this way

The awful number of half-baked proto- and demo-pieces are just an inevitable byproducts of their development strategy.

 

[artis]

SpaceX has taken risks with test articles frequently - often it works (despite "everyone" claiming it cannot work in advance) and ends up being a great solution. In the rare cases where it doesn't work everyone has to shout how SpaceX is stupid, of course.

I'm not saying their stupid, and am not among those that enjoy seeing others fail, anyone who tries hard enough long enough, eventually succeeds or at least gets valuable experience.

What I am saying though is with a rocket like this even without calculation one can be sure there will de destruction of the launch site without proper retarders, absorbers, jets, flame tunnels etc.

Maybe Elon has calculated that rebuilding the site is cheaper than making it reusable in the first place, not sure.
Clearly I do not have the info about the expenses of the project and site and how much for rebuilding although I would estimate that judging by the extensive damage and debris scattering it will cost some money to clean it all up and rebuild.

 

[artis]

So often that I can't help to suspect that they are cutting cost on disassembly and disposal this way

Are you implying that their allowing stuff to blow up on purpose so that no one has to unscrew the bolts and dispose of the materials afterwards?

Either way the huge amount of debris scattered after this launch ain't just gonna disappear on it's own so they will have to pay the guys who will eventually go in and take that scrap out.

 

[Rive]

Are you implying

I'm just ... thinking that while proper disposal of a no longer useful proto of this size is a royal pain in ***, as an alternative they may have considered the ... entertainment value of the thing parallel with the inevitably limited gains from one such test ...

And, to be clear: this thought is not exactly a derogative one.

 

[mfb]

I'm not saying their stupid

Are you sure?

What I am saying though is with a rocket like this even without calculation one can be sure there will de destruction of the launch site without proper retarders, absorbers, jets, flame tunnels etc.

SpaceX did the calculations and estimated that the launch pad would survive. You claim you could have known otherwise before the launch. Without even doing a calculation yourself!

 

[gleem]

Is it known why the plate is oriented at a right angle to the exhaust as opposed to an acute angle so as to deflect the exhaust more effectively?

 

[mfb]

The right angle could come with a lower heat load, keeping the boundary layer of evaporated water there a bit more efficiently. You have this effect in reentry heat shields where a relatively blunt front sees a lower heat load than a spike design. It's definitely lowering the peak heat flow in the center. It's also better in terms of sound.

 

[mfb]

Assembly of the water-cooled steel plate makes progress. The water pipes are gigantic:



Meanwhile Starship SN25 is moving, likely to the launch site for testing. For ships there is a separate test stand, so SN25 doesn't need the orbital launch mount that is being repaired.

 

[mfb]

SpaceX blasted a water-cooled steel plate test article with a Raptor exhaust at their engine test facility:

 

[mfb]

Ship SN25 completed its static fire test, it's likely ready for a flight or at least will be ready well before other components.

The center of the water-cooled steel plate has been installed under the launch mount.
Here are some renders showing how it's getting water.
Once they are done with the launch mount they can put the booster on top and start its test program. That will likely take a few weeks, too.

 

[gleem]

After the launch of Starship Musk said that the second launch would probably occur several weeks after the completion of the modification of the OLM which should be occurring shortly. Also, ship N25 seems ready to go.

Is there any significance of the reluctance of SpaceX to post a tentative/possible launch date as late summer or August TBD, etc.?

 

[mfb]

Too much schedule uncertainty, I think. They will have some plan for the launch mount and booster test campaign but they also need to finish the accident investigation, get FAA approval, and likely need the current lawsuit against the FAA closed.

 

[.Scott]

I'd been under the impression that the water deluge was more/exclusively for sound abatement. Maybe they calculated they didn't need it.

According to SpaceX statements made after the launch attempt, they knew they had to change it and were preparing to do so. They calculated that what they had would be good for one launch.

So they were off by 1.

 

[gleem]

Well the OLM water deluge system has be completed and tested.

 

[Rive]

Well the OLM water deluge system has be completed and tested.

That poor bird there

 

[mfb]

Booster 9 has arrived at the launch site. Launch tower repairs and upgrades must be almost done. About 1 month time to test the booster, a bit of full stack testing and SpaceX might be ready for a launch in late August or early September, pending regulatory approval.



Edit: Booster has been lifted onto the launch mount. A lot of new shielding around the engines.

 

[mfb]

Water deluge system at full power.

The sound is loud 13 seconds into the video.



Different view:

 

[mfb]

They performed a 33 engines static fire test. Out of these 4 shut down early and the test was stopped after 2.7 seconds instead of the intended 5 seconds.
No obvious damage besides a fence that got knocked over. The last time that many engines fired we had a crater below the launch pad, although they fired for longer at that time.
Livestream

Looks like they still need more work on the engine reliability. You don't want to take off with 29 engines - it can be enough to reach orbit but it would reduce the safety margins significantly.

 

[mfb]

SpaceX has submitted its final accident review of the first orbital flight test to the FAA.
The FAA will respond with a list of things SpaceX has to change before the second flight. Once SpaceX has implemented all of them FAA can approve a second launch.

They have worked together closely during the accident investigation so these final reports are generally not surprising either side. It's very likely SpaceX has already implemented many of the changes the FAA wants.

 

[mfb]

Second static fire of booster 9 could happen within minutes.

Edit: Completed. 5-6 seconds at 50% thrust as planned.

 

[mfb]

Starship has been stacked. Musk tweeted (Xed?) "ready to launch, awaiting FAA license approval" but that likely just means they expect to get ready before they get the approval.
For the first flight, stacking was followed by a wet dress rehearsal (WDR), then they unstacked the ship to prepare the flight termination system (FTS) and restacked. It's possible they'll work on the FTS with a stacked ship now and they *might* skip the WDR, but as they don't have an approval to launch yet we could see more tests.

 

[mfb]

FAA Closes SpaceX Starship Mishap Investigation

63 corrective actions identified - most of them will have been developed and already implemented by SpaceX. They are probably done or already done with the list. SpaceX has to declare that they are done, FAA has to accept that, then they can work on a second flight.

 

[mfb]

We got the list (copy here), and SpaceX says they are done with 57 of them, the others are items for later flights:



Now the FAA needs to review that and agree, then they can approve a second flight.

 

[.Scott]

This list was not made public immediately because it contained proprietary and ITAR data. No doubt, that's the reason that all items on this list are very circumspect.

 

[mfb]

Oh sure, that is an edited version of the original list to remove all ITAR-relevant and critical proprietary information.