totm nov 2023 SpaceX Discussion Thread

[tater]

Dunno, when it's closer there will be posts. Sounds like the Australian science channel might have a live feed.

[Rakaydos]

1 hour ago, Spaceception said:

I'm so excited for this, anyone know the time (EST) of the presentation, I don't think I've seen anything yet.

Friday can't come soon enough.

00:30

PST is 930 PM.

As for landing a falcon upper stage... I say nose heat shield, shuttlecock control surfaces adjacent to the MerlinVac, parachutes, and a floating inflated crash bag.

[tater]

 

 

[tater]

Quote

The amount of work yet to be completed on the new TEL means it is increasingly likely the Koreasat 5A will be launched from KSC’s 39A.

Depending on any potential get-ahead work SpaceX can conduct on the 39A TEL inbetween Falcon 9 mission, it is also becoming more unlikely Falcon Heavy will debut in November.

 

[CastleKSide]

On the topic of the AMA, would anyone want to commit to being online then and take a list of questions from us? Most of us are probably unfortunately going to thave to miss it, but that way those of us who have questions could get them answered.

[TheEpicSquared]

6 minutes ago, CastleKSide said:

On the topic of the AMA, would anyone want to commit to being online then and take a list of questions from us? Most of us are probably unfortunately going to thave to miss it, but that way those of us who have questions could get them answered.

When is the AMA? I might be able to. (No promises, though)

[Ultimate Steve]

I'm on reddit, I might be able to ask a question or two provided I'm online at the time. My reddit name is FINALCOUNTDOWN99.

[Spaceception]

https://twitter.com/elonmusk/status/912829943301754880?s=09

Edited September 27, 2017 by Spaceception

[cubinator]

2 hours ago, Spaceception said:

https://twitter.com/elonmusk/status/912829943301754880?s=09

I like how I barely even batted an eye that it's still referred to as BFR.

[Racescort666]

20 minutes ago, cubinator said:

I like how I barely even batted an eye that it's still referred to as BFR.

First AMA question, "does 'BFR' stand for 'big (rhymes with trucking) rocket'?"

[cubinator]

I am writing a theme to the CRS-11 launch. I am quite happy with the countdown and first 16 seconds of flight. I think its hype level is going to leave 2084 and Success in the dust.

Edited September 27, 2017 by cubinator

[Rakaydos]

1 hour ago, Racescort666 said:

First AMA question, "does 'BFR' stand for 'big (rhymes with trucking) rocket'?"

Officially, it's "Big Falcon Rocket"

Any similarity to a common obscenity is ridiculous and you should be ashamed of yourself.

[kerbiloid]

16 minutes ago, Rakaydos said:

Any similarity to a common obscenity is ridiculous and you should be ashamed of yourself.

Why? Their aim is Mars, and BFG was on Phobos. So, BFR = Big Fobos Rocket.

Edited September 27, 2017 by kerbiloid

[Northstar1989]

On 9/23/2017 at 9:27 AM, sevenperforce said:

Flow separation in the full nozzle at sea level would be so catastrophic that the thrust would be completely uncontrollable and would probably rip the nozzle apart.

I don't know what gives you the idea that an over-expanded thrust column is never controllable, but that's simply not true.  NASA has even tested over-expanded nozzles, and in fact the SSME nozzles were slightly over-expanded (that is, they expanded the thrust column to less than 1 atm of pressure- about 0.9 atm I believe).

The result from significant over-expansion (to much less pressure than about 0.9 atm) is greatly reduced Thrust and ISP at sea-level, but NOT the thrust stream becoming uncontrollable.  Such engines DO require a slightly different shape to operate over-expanded though, you ARE right that a nozzle with the shape of the Merlin would be uncontrollable at sea-level.  But a slightly different shape (more bell-shaped if I recall correctly) and the same engine and expansion-ratio WOULD be controllable, albeit with greatly reduced ISP and Thrust in-atmo, if flow-seperation and atmospheric-compression of the thrust column are the only concerns...

Edited September 27, 2017 by Northstar1989

[Grand Ship Builder]

Do we even know what BFR looks like yet?

[Streetwind]

We know last year's design reveal. We don't know how much that may have changed since then.

[cubinator]

1 hour ago, Grand Ship Builder said:

Do we even know what BFR looks like yet?

Big, and stylish. And rocket-y. That much I can assure you.

Edited September 27, 2017 by cubinator

[Nibb31]

1 hour ago, Grand Ship Builder said:

Do we even know what BFR looks like yet?

Were you living under a rock for the last year ? BFR/BFS is ITS.

Edited September 27, 2017 by Nibb31

[Racescort666]

8 hours ago, Rakaydos said:

Officially, it's "Big Falcon Rocket"

Any similarity to a common obscenity is ridiculous and you should be ashamed of yourself.

Touché

Edited September 27, 2017 by Racescort666
French words need accents

[sevenperforce]

4 hours ago, Northstar1989 said:

Quote

Flow separation in the full nozzle at sea level would be so catastrophic that the thrust would be completely uncontrollable and would probably rip the nozzle apart.

I don't know what gives you the idea that an over-expanded thrust column is never controllable, but that's simply not true.  NASA has even tested over-expanded nozzles, and in fact the SSME nozzles were slightly over-expanded (that is, they expanded the thrust column to less than 1 atm of pressure- about 0.9 atm I believe).

The result from significant over-expansion (to much less pressure than about 0.9 atm) is greatly reduced Thrust and ISP at sea-level, but NOT the thrust stream becoming uncontrollable.  Such engines DO require a slightly different shape to operate over-expanded though, you ARE right that a nozzle with the shape of the Merlin would be uncontrollable at sea-level.  But a slightly different shape (more bell-shaped if I recall correctly) and the same engine and expansion-ratio WOULD be controllable, albeit with greatly reduced ISP and Thrust in-atmo, if flow-seperation and atmospheric-compression of the thrust column are the only concerns...

Well, I didn't say that overexpanded thrust columns are never controllable; I said that firing the Merlin 1D Vac with the full nozzle at sea level would cause catastrophic flow separation. Nothing wrong with overexpansion; the problem is severe flow separation.

The SSMEs avoided severe flow separation by bending the nozzle curve back toward parallel at the end, increasing the flow pressure around the edge even though the flow at the center remained overexpanded.

[TheEpicSquared]

On 9/25/2017 at 5:37 PM, Skylon said:

He also said he was going to do a Reddit AMA at the weekend

Do you know a specific time or at least which day? Would be incredibly useful, I have some questions to ask... *cough cough* BulgariaSat landing *cough*

 

On 9/25/2017 at 6:21 PM, CatastrophicFailure said:

Sigh. Once again my Monday starts with "just keep it together till Friday, man."  SMH. 

Isn't that what everyone thinks every Monday?  

[Skylon]

4 minutes ago, TheEpicSquared said:

Do you know a specific time or at least which day? Would be incredibly useful, I have some questions to ask... *cough cough* BulgariaSat landing *cough*

Sorry, I don't know what time; I only said that because of a caption on an Instagram post, which mentioned that he would probably do a Reddit AMA over the weekends.

I might finally create a Reddit account to ask questions.

Edited September 27, 2017 by Skylon

[TheEpicSquared]

7 minutes ago, Skylon said:

Sorry, I don't know what time; I only said that because of a caption on an Instagram post, which mentioned that he would probably do a Reddit AMA over the weekends.

Alright. I'll keep my eyes peeled.

I just realized that a fully fueled Falcon 1 could be lifted to orbit by a Falcon Heavy with ease... which gave me two questions.

1. How much of a payload to LEO increase, if any, could be gained by strapping a Falcon 1 to the top of a Falcon Heavy and making that a new rocket? (Ignoring the obvious issues of aerodynamics, cost, etc. I'm just interested in payload to LEO)

2. How much of a payload to LEO increase could be gained by updating the Falcon 1 to use a Merlin 1D+ while leaving the Kestrel unchanched? (Again, ignoring feasibility and economics completely).

[MajorMushroom]

Can we just take a minute to appreciate how SpaceX reuses its first stage? Here I am struggling to come to a nice (upright) stop on the mun xD

[sevenperforce]

12 minutes ago, TheEpicSquared said:

Alright. I'll keep my eyes peeled.

I just realized that a fully fueled Falcon 1 could be lifted to orbit by a Falcon Heavy with ease... which gave me two questions.

1. How much of a payload to LEO increase, if any, could be gained by strapping a Falcon 1 to the top of a Falcon Heavy and making that a new rocket? (Ignoring the obvious issues of aerodynamics, cost, etc. I'm just interested in payload to LEO)

Increase in LEO payload would be negligible. The increase in gravity losses due to the lower TWR (recall that the Merlin 1D Vacuum already has a TWR < 1 at separation) would wreck any improvements.

12 minutes ago, TheEpicSquared said:

2. How much of a payload to LEO increase could be gained by updating the Falcon 1 to use a Merlin 1D+ while leaving the Kestrel unchanched? (Again, ignoring feasibility and economics completely).

Using the Silverbird Astronautics LV performance calculator, I get 854 kg to a 100x100 km equatorial orbit with Falcon 1 in its first successful launch configuration, using the Merlin 1C. Silverbird usually overestimates slightly; SpaceX had listed the target LEO performance of the Falcon 1 at 670 kg (though I don't know what orbit it allowed). If I swap the 630-kg Merlin 1C (SL thrust of 420 kN) out for a 470-kg Merlin 1D+ (SL thrust: 845 kN), Silverbird bumps up LEO payload to 1031 kg. Adjusting for SB's overestimate would give the "Falcon 1d" (heh) a projected payload of around 808 kg.