Starship is Go...

GW Johnson · 2024-11-26 15:06:19

Supersonic retropropulsion is not the brand new area of investigation that the Angry Astronaut says it is. It's only new if current people at NASA and SpaceX do not understand or appreciate history. Which is apparently the case!

My 1965-vintage edition of Sighard F. Hoerner's opus "Fluid Dynamic Drag" has a plot of drag coefficient versus jet thrust, for a retrorocket plume emanating from the heat shield center of a Mercury capsule shape, tested at Mach 2 in a wind tunnel in 8.2-inch diameter size. The reference Hoerner cites for this plot is a NASA Tech note titled "Thin Retro Jet", TN-D-751, dated to 1961, written by Charczenko. He also gives two other closely-related refences: Wasko "From a Sphere" TN-D-1535, and Peterson "Four Retrorockets" TN-D-1300. These citations did not give a date. The 3 relevant citations (numbers 22a, b, and c) are listed on page 20-9 of this edition of Hoerner's book. The plot is Figure 27 in Chapter 20, located on page 20-11 in Hoerner's book.

It is very clear that NASA was doing serious engineering testing of retropropulsion effects in supersonic flow, way back in the early 1960's.

The modern "experts" seem to be unaware of it. Some "experts" they are!

GW

RGClark · 2024-11-28 13:26:10

Oldfart1939 wrote:

Here's a link to the SpaceX notes stating the tower was definitely the issue, as the tower initiated the landing abort into the ocean.
https://www.youtube.com/watch?v=W2R1aFSkHVI&t=13s

https://youtube.com/clip/Ugkx3e2Q0dB6CM … PdrbjRLeLA

The launch video prior to hotstaging says the tower was go for catch. Then later they decided to divert. The tower issue wasn’t known immediately? Also, The voiceover says the boostback back burn should last another approximately 30 seconds, but then it ends immediately after she says this. Did the boostback end early?

Bob Clark

Last edited by RGClark (2024-11-28 13:33:11)

tahanson43206 · 2024-11-28 14:25:08

For RGClark....

Your question about the diversion may be of interest to others.

Gemini is a Google extension to it's search engine. I decided to ask Gemini but the result was disappointing.

My expectation is that the diversion was performed entirely by the automation. No human could possibly process the avalanche of data that is flowing as the booster approaches the tower.

That said, there is sure to be someone who thinks a human could have been involved.

Here is what Gemini offered:

Conversation with Gemini
Hi Gemini! Thanks (again) for the assistance you have provided in the past. Today I'm hoping you can do a little detective work. A small group of supporters of the US space program, and particularly Starship, are wondering if anything more has been published about the diversion of the Super Heavy from the landing tower. There is at least one report that a computer made the decision to divert the ship to the Gulf of Mexico because the antenna was damaged by the liftoff. I'm sure no humans were involved in making the decision, but can you confirm that?

There have been reports that the Super Heavy booster's diversion to the Gulf of Mexico was triggered by a computer due to damage to the antenna during liftoff. However, SpaceX has not released an official statement confirming the cause of the diversion. It is possible that the decision was made by a combination of automated systems and human operators.
Thanks for your response. What is the cutoff for the information you reviewed?
My knowledge is constantly being updated, so I don't have a specific cutoff date. However, it's important to note that I rely on information that is publicly available. SpaceX hasn't officially confirmed the cause of the Super Heavy booster's diversion, so there might be more details that haven't been released yet.
Thank you for this update. We'll just have to be patient. Do you have any details about the damage to the antenna system?
There have been reports of damage to the antenna system on the Super Heavy booster during liftoff. However, SpaceX has not released an official statement confirming the cause of the damage or the extent of the damage. It is possible that the damage was caused by the extreme heat and pressure of the rocket engines.

(th)

RGClark · 2024-11-28 15:46:11

Robert Zubrin’s made a key statement in this SpaceWatch.Global interview that Elon told him SpaceX could build Starship for $10 million, https://x.com/spacewatchgl/status/18559 … 41756?s=61.

This leads to a surprising conclusion:

SpaceX can build a Moon or Mars rocket for ca. $10 million. Now.
Such a rocket could offer costs of $100/kilo to orbit. Now.

SpaceX routine orbital passenger flights imminent.
http://exoscientist.blogspot.com/2024/1 … enger.html

Bob Clark

Last edited by RGClark (2024-11-28 15:46:34)

GW Johnson · 2024-11-29 09:19:52

Well, they do have to make it all work, and then they must show it all to be reliable, before people ride it. We do that same process with new airplane designs, because it is the right thing to do.

Myself, I take claims like that with a bucket of salt. Musk dollars to do things seem to be off from reality by a similar large factor as Musk time to get something done.

GW

Void · 2024-12-01 11:56:49

You have to tolerate a lot of off topic stuff in this video to get the heat shield stuff, but it is interesting. Apparently, SpaceX is looking into various types of active cooling. I like that as the attitude apparently is "Whatever Works".

https://www.youtube.com/watch?v=ANITE9MFlGA
Quote:

Elon Musk REVEALS New UPDATE: Metallic Heat Shield Will END Ceramic Tiles!
Space Frontier
3.88K subscribers

They mention several types of active cooling.

Gas, Liquids, and then evaporating films.

I am glad that they did everything they could to fix the flaps hinge problem, without resorting to a gas flow, but I have felt that they could flow Ullage gas into the hinges to cool them. They even might flow gas though the flaps themselves. I have even felt that they could have a "Cold Gas Thruster" incorporated into the flaps themselves. This might be OK if the hinges do not leak too much, so that at least part of the flow would go through the flaps. In this way the flaps as thrusters could be pointed. Then they may be useful even before entering the atmosphere.

In the interest of making a machine that can fly repeatedly with reduced maintenance they will likely use a variety of methods.

Ending Pending

Last edited by Void (2024-12-01 12:16:47)

tahanson43206 · 2024-12-01 19:22:43

For Void re #1981

kbd512 and I are just curious ... you may have been logged in when kbd512 pulled the plug on the old system.

Did you notice anything, or were you safely logged off when that happened?

(th)

Void · 2024-12-01 19:56:19

I did OK. I discovered I could not get in, there was a message about service of the system.

Ending Pending

tahanson43206 · 2025-01-16 15:46:58

This topic has been quiet since Void checked in on December 1st of last year.

Today, 53 minutes from now (16:43 local time) SpaceX is hoping to try again with Test flight 7..
The vehicle looks significantly different to my eye, so I'm looking forward to detailed reports that will be arriving soon.
It also appears that a second launch tower is standing, as predicted for tests of two vehicles planned for 2025.

Here some notes from The New York Times:

For the Starship on this seventh test flight, significant design changes were made to the propulsion, the heat shield and the control systems. The rocket has been stretched several feet taller than earlier Starships — space for bigger tanks that hold 25 percent more propellant.41 mins ago
SpaceX's 7th Starship Test Launch: What to Know

In the full article I found a report that the nose fins have been moved closer to the nose.

(th)

GW Johnson · 2025-01-16 17:02:39

Launch and booster recovery went well. No vent fire this time after catch. Contact with ship lost just before end of ascent burn. One after another of the vacuum engines dropped out, along with the 3 sea level engines, right up to lost contact showing 1 vacuum engine still burning, but speed and altitude indications not changing. I noticed the methane-remaining indication looked low compared to the oxygen.

Loss of ship not confirmed as I type this, but it really looks like it was lost, and the SpaceX commentators said so.

Update moments later: loss of ship confirmed.

GW

Last edited by GW Johnson (2025-01-16 17:03:44)

Oldfart1939 · 2025-01-16 18:24:22

An amazing "day," although I slept quite a time between the Blue Origin launch and SpaceX flight 7!
My observations: Both ships had beautiful liftoffs and easily cleared their towers; the BO "New Glenn" was a lot slower in it's acceleration, probably due to, a much lower T/W ratio. Scott Manley did a reverse engineering type estimate of maybe a 1.16-1.2 thrust to weight ratio, whereas Starship has power to spare and got outta Dodge a lot faster, in spite of carrying an additional 300 tons of propellants in the new Version 2 Starship. Both boosters performed beautifully up to and through stage separation, and second stages initially looked to be in great shape. The Glenn BE-3 engines seemed to do a very good job and did the necessary relights in vacuum, thereby propelling the upper stage into an initial orbit successfully. The SpaceX booster, or Super Heavy, did a beautiful flip and boost back burn, on course for Starbase, and completed a spectacular tower catch. New Glenn first stage did a boost back burn successfully, but according to BO, telemetry was lost and the stage was presumed lost while attempting to land. I was already in bed when BO second stage completed it's high orbit insertion.
SpaceX began seeing the velocity increase begin slowing and engine out indicators, leading to loss of the second stage and a failed recovery.

Oldfart1939 · 2025-01-17 00:36:12

I just saw an update re: Ship 33; the Starship 33 experienced an onboard fire thought to involve leaking Oxygen and methane which was initially detected by onboard cameras. There was a massive RUD over the Turks and Caicos Islands and there are some very cool photos of the debris reentering the atmosphere. There is also a call number provided so that anyone finding debris can notify SpaceX for it's recovery. Thankfully there has been no report of any injuries, since the RUD and debris fallout occurred within the designated exclusion zone for possible reentry.

Here's a link to Scott Manley: https://www.youtube.com/watch?v=vfVm4DTv6lM

Last edited by Oldfart1939 (2025-01-17 00:56:05)

GW Johnson · 2025-01-17 09:44:32

I thought perhaps there must have been some sort of leak and fire in the engine bay, because of the low methane-remaining indication. So it would seem that such actually happened.

This is from today's "Daily Launch" email newsletter from AIAA:

NEW YORK TIMES
SpaceX Starship Rocket Is Lost During 7th Test Launch, Causing Debris to Fall

The seventh test flight of SpaceX’s Starship rocket failed on Thursday as the vehicle’s upper stage experienced a catastrophic malfunction as it headed upward to space. SpaceX was able to achieve some success by repeating the feat of catching the gargantuan Super Heavy booster back at the launchpad.

---
back to me:

Takeoff thrust to weight needs to be adequate so that you achieve some significant speed while you burn off around half your propellant. If you fail to do that, your gravity loss is much higher, reducing what payload you can carry. The rule of thumb is that you need around half a gee net vertical acceleration above gravity in order not to be very inefficient. For Earth launches, that's a takeoff thrust/weight = 1.5. Higher is even better, but usually only obtainable with all-solids.

That thrust/weight is limited by how much thrust you can pack into the space available for engines at the base of the stage, limited primarily by expansion bell exit diameter, and compounded a bit further by gimballing angle requirements. For a given area expansion ratio (and thrust coefficient), that sets your throat area. Thrust is Pc At CF. Smaller Pc means bigger At, since CF is fixed. That in turn means bigger Ae, which limits how many engines you can have, which limits adversely your takeoff thrust and thrust/weight.

Higher Pc is beneficial, but very difficult to achieve. That's why the modern engines fall in the 2000-4000 psia Pc range, while the older designs were in the 500-2000 range. And why they cost so much to develop. I know the Raptors are near 4000 psia Pc. I don't know what the Pc is for BE-4's.

GW

Last edited by GW Johnson (2025-01-17 09:52:58)

Oldfart1939 · 2025-01-17 11:41:41

GW-
According to various reports I've seen, the BO BE-4 engines are running at about 80% of their design pressure limits to extend their lifetimes; so--that accounts for the lower performance and lots of fuel burn overcoming gravity in the early stages of flight. I suspect that they will need to increase the chamber pressures to take advantage of the undoubtedly better performance (which IS available) needed in later flights.

According to comments by Scott Manley, the second stage of IFT-7 was veering off course due to the loss of steering capability, and probably triggering the flight termination system. Of all the usual live space website analysts, he undoubtedly does the most thorough and scientific reporting.

RGClark · Today 11:15:00

Agree or disagree: it was a mistake for SpaceX to follow the failed Soviet N-1 approach to testing Starship. A Raptor failed both on the booster and on the ship, and on the ship one failed catastrophically. How many total test flights needed now just to make orbit with high payload? 10? A dozen? How many total to prove Raptor reuse reliability? 15? How many total to prove orbital refueling? 20?
In contrast standard industry practice is to construct a separate, full test stand to do full up, full thrust, full duration testing. Done this way at least Starship could be doing expendable flights already by now, and with paying customers. Even Raptor reuse reliability could have been tested on the full test stand, providing a faster route to Starship reuse.

Bob Clark

RGClark · Today 11:17:06

Oldfart1939 wrote:

GW-
According to various reports I've seen, the BO BE-4 engines are running at about 80% of their design pressure limits to extend their lifetimes; so--that accounts for the lower performance and lots of fuel burn overcoming gravity in the early stages of flight. I suspect that they will need to increase the chamber pressures to take advantage of the undoubtedly better performance (which IS available) needed in later flights.

Do you have a source for that? If Blue Origin wants to increase their payload to the planned 45 tons, they’ll need to increase the thrust.

Bob Clark

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#1976 2024-11-26 15:06:19

Re: Starship is Go...

#1977 2024-11-28 13:26:10

Re: Starship is Go...

#1978 2024-11-28 14:25:08

Re: Starship is Go...

#1979 2024-11-28 15:46:11

Re: Starship is Go...

#1980 2024-11-29 09:19:52

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#1981 2024-12-01 11:56:49

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#1982 2024-12-01 19:22:43

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#1983 2024-12-01 19:56:19

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#1984 2025-01-16 15:46:58

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#1985 2025-01-16 17:02:39

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#1986 2025-01-16 18:24:22

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#1987 2025-01-17 00:36:12

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#1988 2025-01-17 09:44:32

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#1989 2025-01-17 11:41:41

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#1990 Today 11:15:00

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