New Mars Forums

About my riddle, the first solution to the riddle comes out of the assumption that from its economy of size that SuperHeavy/Starship will be THE be-all, end-all for ALL of spaceflight. In point of fact, for EVERY form of transport going back to the horse-drawn era, the transport has always come in different sizes. 

The point is well illustrated by the example of the jumbo jets. See the highlighted sentence in the article:

 The largest jumbo jets actually make up a *tiny* proportion, less than 1%, of total air traffic. 

The same is true of car traffic. The amount of traffic carried by Greyhound buses is a tiny proportion of the traffic carried by passenger cars.

Sure, the bus companies and the jumbo jet airliners would love if the majority of passengers were on their vehicles, but THATS NOT WHAT THE CUSTOMERS WANT.

The airline companies know this of course. The same airline companies that operate the jumbo jets also operate the smaller aircraft. If those airline companies were to only offer the jumbo jets they would rapidly go out of business.

ArianeSpace found a similar phenomenon with the Ariane 5. It was designed to carry separate satellites to orbit. But what they frequently found is that when one satellite was ready to go, ArianeSpace had to wait around for another satellite ready to go for it to be worth launching the Ariane 5. And in point of fact most satellite companies wanted their OWN DEDICATED LAUNCHER.

That is the primary reason why ArianeSpace wanted to move to the Ariane 6, so customers could affordably have their own dedicated launchers.

The Falcon Heavy gives further evidence of this. The per kilogram cost of the FH is less than the F9. If per kilogram cost was the key thing, then the Falcon Heavy would packed with separate satellites and would be launching as often as the F9. But in point of fact, FH launches have been few and far between, and have only been used when there are satellites that can’t be launched on the smaller launchers, including the F9. As before, the satellite companies want their own dedicated launchers.

SpaceX might claim their per kilogram cost will make them preferred but the example of the bus companies and the airlines make that argument extremely dubious. Their own Falcon Heavy also argues against it. 

Also, I don’t agree their per kilogram cost will in fact be that much cheaper than the other New Space companies. For those other companies know SpaceX was able to cut development cost by 90% by the commercial space approach, i.e., getting private financing rather than government financing. 

Then consider: when pricing their launch vehicles the largest proportion of that price is not coming from the production cost, but in fact due to the amount added on to recoup the development cost over time. 

SpaceX has spent $10 billion developing the SuperHeavy/Starship with more billions yet to be spent on the development. This is in the range of 100 times higher than the development cost for the companies with smaller launchers. Then the amount to be added on to the price due to development cost, which again makes up the largest bulk of the customer price, will be radically smaller. 

Note that SpaceX won’t be superior in price reduction due to reusability either since all the New Space companies also are focusing on reusability.

  Robert Clark

Brain Teaser: Why does Falcon Heavy disprove the SpaceX justification for building the SuperHeavy/Starship?
MAJOR hint: Why did Arianespace want to move away from the Ariane 5 to the Ariane 6?

After writing that, it occurred to me there are two different answers to my riddle. Hint for 2nd answer: how many Merlin’s flew on actual operational missions on Falcon 9’s before the Falcon Heavy flew? How many times did the Raptor before the SuperHeavy/Starship?

  Bob Clark

In addition to the three alarming facts about the launch I discussed in post #63 there was another fact just as alarming, the lean the rocket initiated soon after launch. It was assumed this was commanded by launch control. But Elon revealed this was done by the rocket itself to compensate for the 3 shut down engines:

Elon Musk pushes for orbital goal following data gathering objectives during Starship debut
written by Chris Bergin May 3, 2023
…
“Those engines did not explode, but they were just, the system didn’t think they were healthy enough to bring them to a full thrust,” added Musk during a post-flight Twitter spaces call, adding that is why the vehicle appeared to lean away from the Tower during ascent.
It was assumed the lean could have been related to pad avoidance, but Musk quickly noted that it is undesirable due to the “blowing torch” of the Raptor 2 engines on the OLM ring.
“If you move sideways sooner, you are moving that big, cutting torch across the launch ring. So, you can think of this thing like the world’s biggest cutting torch, basically. Depending on how close the engines are, they erode that steel at a roughly — I think half an inch to an inch per second of high strength steel is eroded by the cutting torch.”
“(The lean was actually) related to the engines out, and we do not normally expect to lean. It should be aspirationally going straight up.”
https://www.nasaspaceflight.com/2023/05 … hip-debut/

This is extremely concerning because if this really was a fully automated compensation maneuver then if the shut down engines were on the other side the lean would have been towards the launch tower! The result would have been a catastrophic explosion.

  Bob Clark

Angry Astronaut on the off-shore launch idea for Starship. He notes it has been done before:

Starship and the Deimos Launch Pad- the PERFECT plan for SpaceX! Lessons from history prove it.
https://www.youtube.com/watch?v=ZeQO_4RLBTk

  Bob Clark

This video appeared in my Youtube video feed:

https://www.youtube.com/watch?v=RSkz-9RPN4Y

The description that appears overlaid on a still from the video prior to starting the video is, "It was sabotage!" That description is clickbait. The video itself says nothing of the sort.

   Bob Clark

That was a little uncalled for. The decision to not use a flame diverter was made years ago. Elon overruled SpaceX engineers who wanted to include one. This was a cost decision not based on engineering.

To add a flame diverter trench would indeed be expensive. The reason is the closeness of the water table means you would have to raise the launchpad to insert the flame trench below it. Then that means you have to also raise the launch tower. So you would have to dismantle it section by section. Then you would place an additional section below it. Finally, you restack the original sections atop the new section.

You can understand why Musk would not want to pay for that. But it’s needed then it has to be done.
The same is true for building a separate ALL engine, FULL thrust, FULL flight duration static test stand. It will be expensive, but it’s needed and must be done.

There is an alternative approach without those two additional expensive developments. They could launch from an ocean platform 20 miles off-shore as originally intended planned. That way SpaceX could launch and destroy as many copies of the SH/SS they want, like was done for the N-1.

  Bob Clark

Three quite alarming facts were revealed in Elon’s twitter Spaces discussion:

Elon Musk - Spaceship update after explosion - Spaces Twitter.
https://www.youtube.com/watch?v=pe4B2eIeXfs

First, the Raptors likely were not damaged by the concrete thrown up. If so, then 8 Raptors failed on their own during the flight. Second, thrust vector control, TVC, failed at some point during the flight. Third, the FTS took far too long to destroy the vehicle at 40 seconds.

These three facts together could have led to catastrophic results to the public. If that many Raptors had failed and without TVC closer to the ground, the FTS would not have been able to destroy it before it was over densely populated area if headed in that direction.

The multiple failures of Raptors during tests, and not just shutting down or being shut down, but actually leaking fuel and catching fire, led to my arguing SpaceX should be required by the FAA to construct a separate all-up test stand for full thrust, full flight duration testing. Had this been done then both the launch pad damage and the likely Raptor failures would have been picked up.

I also argued there should be an independent review aside from the FAA by space safety experts on the safety of the launch. If so, the inadequacy of the FTS likely also would have been picked up. I say it’s likely it would have been seen beforehand because assuming the FTS did activate there seems to be only one reason why it did not destroy the vehicle immediately: the strength of the explosives used were not sufficient to penetrate beyond the tank wall strength. This SHOULD have been seen beforehand.

Tank wall thickness depends on the width of the tanks and the material used. Because of its size, the closest analog to the SuperHeavy stage was the Saturn V’s  S-1C first stage. It’s max wall thickness was in the range of ~6.5 mm while for the SuperHeavy it’s in the range of ~8mm, about 25% thicker. BUT it’s also important to remember the specialty high strength stainless steel used on the SuperHeavy is much stronger than the standard aerospace grade aluminum used on the S-1C.

Given the greater thickness and greater material strength, these two facts together give a tank wall tensile strength for the SuperHeavy about 3 times higher than that of the S-1C. The amount of explosives used should have been adjusted accordingly.

I discussed the inadequacy of the safety review in the first post of this thread:

SuperHeavy+Starship have the thermal energy of the Hiroshima bomb. UPDATED, 3/8/2023.
https://exoscientist.blogspot.com/2023/ … nergy.html

Key Points.
1.)While the explosive force of the SuperHeavy/Starship (SH/ST) is not likely to reach that of its full thermal content of 13.3 kilotons of TNT, comparable to the Hiroshima bomb, it is still likely to be in the range of 3 to 5 kilotons of TNT.

2.)The Halifax and Texas City disasters of comparable explosive force suggests damage can extend kilometers away.

3.)The hazard or exclusion zones of only 2 miles, 3 km, for SH/ST is likely inadequate based on the Halifax and Texas City disasters.

4.)SpaceX ignored FAA warnings not to launch SN8 due to weather conditions exacerbating the effects of a possible blast wave from an explosion.

5.)The Starship SN11 explosion in midair may have been a BLEVE, which introduces an additional detonation mode for cryogenic fuels.

6.)At least one Raptor leaked methane and caught fire on multiple test flights of the Starship.

7.)Since the SuperHeavy static test lasted little more than 5 seconds, a strong possibility exists that multiple engines will fail during a full burn of an actual flight.

Recommendations.
1.)It should be revealed to the public the SH/ST has the thermal energy content of the Hiroshima bomb.

2.)Experts on launch vehicle explosions and fuel-air detonations should present a report to the public explaining what the likely explosive force would be if the vehicle exploded.

3.)SpaceX should not be granted a launch license for the SH/ST until SpaceX constructs a separate engine test stand sufficient to test all 33 Superheavy engines at the same time at full power and at full flight duration, and for such tests to complete successfully for multiple tests.

Make no mistake, this is on the FAA as well as on SpaceX.

   Bob Clark

Looks like 8 engines out in this frame based on the fact the outer ring should have 20 engines firing, so it’s missing 6, and the inner ring should have 3 engines firing so it’s missing 2, though one of the inner ring engines may be partially firing:

   Bob Clark

I wanted a separate static test stand for all 33 engine engines constructed because I had no confidence all 33 Raptors would burn for the full flight duration. The idea of damage to the pad from the demolished concrete from the thrust was not even on my radar.

But if the full test stand had been constructed, this is another major flaw that would have been picked up beforehand.

   Bob Clark

What they’re discussing at SpaceX right now, “Ok, whose bright idea was it not to have a stage separation mechanism?”

This article discusses the decision not to have a stage separation mechanism:

https://www.teslarati.com/spacex-starsh … -extremes/

An unfortunate decision because if the stages did separate there might not have been any need to send the destruct signal. Plus, you would have gotten far more data by seeing what the Starship upper stage could do.

  Bob  Clark

Further on safety issues of the SpaceX Superheavy/Starship launch:

SuperHeavy+Starship have the thermal energy of the Hiroshima bomb, Page 2: shattered windows and flying shrapnel.
https://exoscientist.blogspot.com/2023/ … nergy.html

Key Points

1.)For both shattered windows and flying shrapnel there has to be a statistical distribution given for the distances these can occur, not just a single number, since at even distances commonly given as "safe" some proportion of these can happen beyond that distance.

2.)The 5 km exclusion zone is almost certainly inadequate for shattered windows and flying shrapnel if there were to be an explosion since there is a high statistical chance both can happen beyond this distance, especially for larger size windows, such as the plate glass windows common in stores, commercial properties, and hotels.

3.)The Mexican border is closer to the launch site than 5 km, making it even more likely shattered windows and shrapnel can reach there in the event of an explosion.

4.)Since Mexican citizens might be harmed, SpaceX might cause an international incident if there were an explosion. Therefore, unlike any launch ever undertaken previously by the U.S, the State Department needs to be informed of the possibility of damage on the other side of the U.S./Mexican border, so they won't be blindsided if it does occur.

Recommendations.

1.)Despite SpaceX's desire to have routine, common launches, because rocket engines operate at such extreme levels of temperature and pressure, they are unlikely ever to have the same reliability of for example jet engines. Then it is unlikely the SuperHeavy/Starship combination will ever be safe enough to launch from the Boca Chica site.

2.)Then SpaceX should consider alternatives. Indeed, they first proposed that the launches would take place 20 miles off-shore because of noise concerns for such a large rocket. The safety concerns in case of an explosion are even more pressing to not allow the launch so close to populated areas.

3.)Another approach SpaceX could take is a triple-core arrangement for their large rocket, a la the Falcon Heavy. They would first make a smaller rocket using the Starship this time as a first stage and a smaller mini-Starship as the upper stage. Note, the Merlin engines flew over 1,000 times on actual missions on the Falcon 9, before the Falcon Heavy even flew.
In contrast, the way things are now SpaceX wants to use the Raptor engine on the largest rocket ever built without the Raptor having flown a single time to actual space. And this for engine that failed or caught on fire multiple times in tests.
When SpaceX wanted to proceed to the triple-core version, because of its size it would still need to be launched off-shore, but judging from the example of the Falcon 9 and Falcon Heavy, the single core will fly many more times than the triple-core version in any case.

  Robert Clark

A major problem is nuclear thermal rockets have very poor thrust/weight ratios, like in the single digits. Chemical rocket engines typically have T/W ratios in the range of 70 to 1 for hydrolox or over 100 to 1 for kerolox.

But we did discuss on Newmars that both CO and O2 exist in the Martian atmosphere, though in small amounts. But CO can react with O2 to generate energy. The question is can they be separated out and compressed on the fly, so to speak, to generate net power for a Martian airplane?

  Robert Clark