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I have no objection to SpaceX performing full scale test flights before perfecting the Raptors reliability. It’s their money they can spend it anyway they want. I just don’t want them doing those full scale test launches within 5 miles of populated areas. If they want to do those test launches 20 miles off shore that would be perfectly fine.

By the way, I made the argument also on Reddit that the desire to meet the Artemis III launch schedule puts undue pressure on the SpaceX safety procedures. I got the response Artemis does not add any more pressure to the engine/Starship development than SpaceX has created for themselves by making Starship crucial for their business model (Starlink).

However, if it is the case the need to be profitable rapidly is driving the approach SpaceX is taking developing the SH/ST, then that’s even worse since the public safety is being risked on the basis of SpaceX fast profitability.

  Robert Clark

SpaceX should withdraw the SH/ST from Artemis III consideration because it is leading them to compress the normal testing process of getting engine reliability. The engineers on the Soviet N-1 Moon rocket were under the same time pressures in launching the N-1 before assuring engine reliability in order to keep up with the American's Moon program. The results were quite poor.

The difference was the N-1 launch pad was well away from populated areas. On that consideration, you can make an argument the scenario SpaceX is engaging in is worse than for the N-1.

After SpaceX withdraws from Artemis III, if they want to spend 10 years perfecting the Raptors reliability before doing another full scale test launch that would be perfectly fine.
(They could also launch 20 miles off shore as originally planned.)

Robert Clark

Thanks for responding. My sig file was stating the opinion the Old Space companies will find a way to make anything they are contracted for cost billions of dollars even if commercial space could do it for a hundred million or even for just a few tens of millions.

About the Superheavy/Starship, much discussion has been over comparing it to the multiply failed N-1 rocket. Starship defenders deny this comparison because the N-1’s rocket engines were not properly tested. The key point I’m making is that even though the Raptor engines are individually tested they still have a 1 in 4 chance of failing on an actual flight.

The upshot is for all practical purposes the SH/ST is like N-1 rocket in that it will be launching with engines with poor reliability.

This can have catastrophic results. Elon has been talking like he wants to relaunch, like, tomorrow. But nobody believes the Raptor is any more reliable that it was during the April launch. It is likely such a launch will fail again. The only question is when. This is just like the approach taken with the N-1 rocket. Four engines having to shut down on the recent static fire after only 2.7 seconds does not inspire confidence; it does the opposite. Either the Raptor is just as bad as before or the SpaceX new water deluge system makes the Raptor even less reliable than before.

Since nobody knows when such a launch would fail, it is quite possible it could occur close to the ground. The public needs to know such a failure would likely be 5 times worse than the catastrophic Beirut explosion.

  Robert Clark

An alternative approach to an Artemis landing would not need the Starship HLS so would save NASA $3 billion. In fact, NASA would not have to pay for the lander at all:

Possibilities for a single launch architecture of the Artemis missions, Page 2: using the Boeing Exploration Upper Stage. 
https://exoscientist.blogspot.com/2023/ … aunch.html

Possibilities for a single launch architecture of the Artemis missions, Page 3: Saving the lander mission for Artemis III.
http://exoscientist.blogspot.com/2023/0 … ch_11.html

  Bob Clark

Perhaps Stoke Space should mention noted rocket designer Philip Bono was the originator of the idea of using a plug nozzle for cooling on reentry:

https://en.wikipedia.org/wiki/Philip_Bono

It would be wise also to note Bono used the increased efficiency of an aeroplug/aerospike on launch in his designs rather than dismissing it.

History of the Phoenix VTOL SSTO and recent developments in single-stage launch systems.
January 1992
Authors: Gary Hudson

https://www.researchgate.net/publicatio … ch_systems

This is important because doing a delta-v calculation via a rocket equation a hydrolox stage like the Stoke Space stage with a 10 to 1 mass ratio, a la the Centaur stage, could actually reach orbit with an aerospike nozzle.

NASA proved 20 years ago that the aerospike works by actually building it and testing it:

XRS-2200/RS-2200 LINEAR AEROSPIKE ENGINE DATA SHEETS.


http://heroicrelics.org/info/aerospikes … -2200.html

  Bob Clark

Thanks for that summary of new European launch start-ups. Too bad Virgin Orbit is not still here. I looked at the available info on their air-launched two-stage rocket, and it turns out it would have comparable payload to the SpaceX Falcon 1 and Rocket Lab Electron, in the few hundred kilo to LEO range, just by launching from ground, no air launch required.

For both SpaceX and Rocket Lab though they spent less than $100 million developing their first rockets. But Virgin Orbit spent $400 million. I think requiring the use of that aircraft contributed to that high development cost, and contributed to their bankruptcy.

Launch from Europe presents difficulties though. You want to launch eastward to take advantage of the Earths rotation to maximize payload. But you would overfly dense populated area, including neighboring nations that way.

That was one of the advantages of air-launch that it could fly to a launch position that would not overfly populated areas when the rocket was launched. At least for Virgin Orbit there would have been a convenient solution for ground launch though: partner with one of the former British colonial islands in the Caribbean for a launch site. The British Virgin Islands would have been especially appropriate :-).

  Bob Clark

The underlying basis of my proposal to dispense with the SRB’s on the Ariane 6 was their high cost made the Ariane 6 pricing and non-reusability just as bad as the pricing and non-reusability on the ULA launchers, the Delta IV and Atlas V, which put ULA on the brink of bankruptcy. Any variation of the topic of cost/capability of solids vs. liquids is perfectly fine.

Actually, small solids as addendum to the liquid-fueled core engines could be quite cost effective. BUT they have to be small and serve as an addendum to the thrust of the core engines, not provide the major portion of the thrust of the rocket.

So in my all-liquid version of the Ariane 6 I spent quite a bit of effort to find ways the two Vulcains would have sufficient thrust for lift-off, chiefly by using an upper stage 1/3rd the size of the current version of the Ariane 6 and also by assuming the Vulcain thrust could be ramped up 9%. But if small side boosters 1/10th the size of the current Ariane 6 SRB’s were used that would be cost effective as addendum to the two Vulcains thrust. That way, we could use the original large size upper stage and thereby get larger payload. The side boosters now being normal sized, 1/10th the core stage size, they would now also be low cost. Instead of adding €40 million($44 million) to the cost launcher cost, they would add only €4 million($4.4 million) to the cost.

With the side boosters now being normal sized, and normal priced, you could have variations on the configuration of the Ariane 6 launcher: without SRB’s, with two small SRB’s, or with four small SRB’s. Like is the case with the Delta IV and Atlas V.

However, as I mentioned the primary reason why ESA wants to use the large sized boosters is politics, and not to be cost effective. The ESA member states making the SRBs want them to be high cost, because that way they get high revenue returned to them with each launch. It is extremely dubious they would sign off on a non-SRB Ariane 6 for that reason, but these are two of the most powerful ESA states that make the SRB’s. Even the scenario with 1/10th the SRB size is also doubtful for the same reason, the greatly reduced revenues they would get with each launch.

Anyone who has lived in the world to adulthood knows politics stupefies everything. (Yes, I know that is not the proper usage of “stupefy” but it gets the point across.)

  Robert Clark

  Thanks. I’ll give that a try.

   Robert Clark

The comparison to be made is to the Falcon 9, not to the Delta IV or Delta IV Heavy. If ArianeSpace only had to worry about those two Old Space launchers they would be quite happy since they are also overpriced.

The currently cited prices of the Ariane 6 are €75 million($80 million) for the Ariane 62 and €115 million($125 million) for the Ariane 64. Those prices are 2 to 3 times the price of the Falcon 9 used price. There is no way ArianeSpace will be able to survive offering commercial launches at those prices. They’ll either go bankrupt outright or, like ULA, offer themselves up for sale to prevent bankruptcy.

  Robert Clark

I’m glad they started adding that disclaimer to the ChatGPT responses.

Openrocket and Rasaero are used by amateur solid rocket makers to estimate the altitude their rockets can reach. They can only calculate altitude for a rocket going straight up. They can’t do a rocket that must follow a curved trajectory to reach the needed horizontal, i.e., tangential velocity for orbit.

I looked at CEARUN and the only use I found on the web site is for calculating performance of rocket engines given propellant, chamber pressure, etc. I’d like to use a trajectory optimization option if anyone can find it on the web page.

For “Systema” I haven’t been able to find it after a web search. ChatGPT has been known to literally invent references that don’t exist. Several researchers have noticed this odd bug in the program. And in one case a lawyer was censured by a judge for citing references in a legal filing he got from ChatGPT that didn’t actually exist.

  Robert Clark

Copied below is the abstract to the blog post:

Towards a revolutionary advance in spaceflight: an all-liquid Ariane 6.
Abstract.

Most orbital rockets have payload fractions in the range of 3% to 4%. The Ariane 6 using 2 and 4 SRB’s, because of the large size of the SRB’s and because solids are so inefficient on both mass ratio and ISP, the two key components of the rocket equation, it will count among the worst rockets in history at a payload fraction of only 2%.

In contrast a two Vulcain Ariane 6 could have a payload fraction of 7% and a three Vulcain Ariane 6 could have a payload fraction of 7.5%. This is well-above what any other rocket has ever achieved in the history of space flight.

So how is an all-liquid Ariane 6 able to accomplish this? First, this version is based on the Ariane 5 core. The mass ratio for the Ariane 5 it turns out is quite extraordinary for a hydrogen+liquid oxygen(called “hydrolox”) stage at 16.3 to 1. This is in the range commonly seen by dense propellants. To use a colorful analogy, it’s like the ArianeSpace engineers in designing the Ariane 5 core found a way to make liquid hydrogen as dense as kerosene!

Obviously, this is not what happened. But they must have found a way to achieve extreme lightweighting of a hydrolox stage. To put this in perspective, the mass ratio of the famous Centaur hydrolox upper stage is at 10 to 1, achieved back in the 1960’s. And the Delta IV hydrolox core is at a quite ordinary 8.7 to 1 mass ratio. So the Ariane 5 core is about twice as good as the Delta IV core on this key mass ratio scale.

Because the Ariane 5 core has the high Isp of a hydrolox stage while achieving (somehow!) the high mass ratio of a dense propellant stage, it calculates out to have the highest delta-v of any rocket stage in the history of spaceflight.

Since delta-v is the single most important parameter for orbital rockets, you can legitimately argue the Ariane 5 core is the greatest rocket stage ever produced in the history of spaceflight.

The high 7.5% payload fraction of the all-liquid Ariane 6 would mean SpaceX would have to be chasing ArianeSpace rather than the other way around.

To put this advance in perspective, it would be like SpaceX using the very same Merlin engines and the very same propellant tanks, and the very same size Falcon 9, suddenly being able to change the Falcon 9 payload from 22 tons to 40 tons.

It will represent a paradigm shift in terms of the payloads that rockets will be expected to deliver to orbit.

Usually, when we think of a radical shift in rocket capability we imagine some great advance in engines such as nuclear, or some great advance in materials to greatly reduce tank weight.

Quite extraordinary is the the fact this radical increase in rocket capability can come from using currently existing engines and tanks.
https://exoscientist.blogspot.com/2023/ … ce-in.html

  Here’s a delta-v calculation for the two Vulcain case:

The rocket equation uses the ISP of a rocket stage and uses the propellant mass and dry mass of the stage. For the two stage vehicle the calculation looks like this:

434*9.81Ln(1 + 158/(12 + 13 + 14)) + 465.5*9.81Ln(1 + 11.8/(1.2 + 14)) = 9,500 m/s .

Commonly the delta-v to orbit for a hydrolox rocket is taken as 9,300 m/s to 9,400 m/s. This is somewhat more than a dense propellant stage since dense propellants are more efficient for a first stage.

However, there is a big caveat for this delta-v calculation. For the two Vulcain solution, I lowered the upper stage mass and supposed the Vulcain sea level thrust could be ramped up in the 9% range. This was to insure enough take-off thrust-to-weight ratio without SRB’s. The result does give a TWR greater than 1, but it is still low. A low TWR results in a higher delta-v required to orbit because there are higher gravity losses.

So I used instead the payload estimator on the SilverbirdAstronautics.com page. I’ve found this generally accurate to within plus or minus 10%.

Another solution of the low thrust of the two Vulcains is to use SRB’s but of the usual 1/10th the core size. The high cost of the Ariane 6 SBR’s is coming primarily from their large size. If we used SRB’s at 1/10th the size they would be weigh about 15 tons each. They would still provide sufficient thrust for take-off and we could then also use a larger size upper stage.

The result would be a higher payload to orbit than just using the two Vulcains. Keep in mind the entire difficulty with the Ariane 6 is it’s high cost due entirely to those large SRB’s planned to be used. Using instead SRB’s at the normal 1/10th of core size might add instead of $40 million, only $4 million to the price. This would likely result also in a launcher still cheaper than the Falcon 9.

But note well, the ESA like NASA is a highly political organization. The ESA member states making the SRB’s want the high cost for those SRB’s. That means more revenue coming to them for each launch of the rocket. If you cut down the size of them to 1/10th size that would be a great reduction in the revenues coming to them from those solids.

  Robert Clark