totm nov 2023 SpaceX Discussion Thread

[_Augustus_]

Someone on NSF pointed out that the Zuma designation is a codename, and not an acronym, so any speculation as to the payload based on the word "Zuma" is meaningless.

From some further research it appears that SpaceIL doesn't have the money for an F9 launch, and definitely not on a new booster.

On Reddit people are saying it could be an asteroid mining company's prototype spacecraft or something, but those guys don't have money either....

 

Edited October 15, 2017 by _Augustus_

[sh1pman]

Maybe a launch escape system test at max-Q or something like that.

[Exoscientist]

8 hours ago, RedKraken said:

 

  The 70 metric ton dry mass estimate seems high to me. The original ITS tanker, about twice as big, had a 90 metric ton dry mass. So I would expect the BFS dry mass to be closer to 45 metric tons.

 

  Bob Clark

Edited October 16, 2017 by Exoscientist

[PakledHostage]

7 hours ago, Nibb31 said:

Or he's just full of fecal matter. This is reddit we are talking about after all.

 

43 minutes ago, _Augustus_ said:

On Reddit people are saying it could be an asteroid mining company's prototype spacecraft or something, but those guys don't have money either....

 

Q.E.D.

[_Augustus_]

1 hour ago, sh1pman said:

Maybe a launch escape system test at max-Q or something like that.

That won't be until after DM-1.

[tater]

They were gonna use that testbed falcon for the max-q abort (the one with 3 engines).

[Rakaydos]

2 hours ago, _Augustus_ said:

Someone on NSF pointed out that the Zuma designation is a codename, and not an acronym, so any speculation as to the payload based on the word "Zuma" is meaningless.

From some further research it appears that SpaceIL doesn't have the money for an F9 launch, and definitely not on a new booster.

On Reddit people are saying it could be an asteroid mining company's prototype spacecraft or something, but those guys don't have money either....

 

I remember reading that the asteroid mining people (plantary resources) were a secondary payload on the AMOS rocket explosion. Perhaps they got a free rocket from spaceX for waiting?

[Bill Phil]

3 hours ago, Exoscientist said:

 

  The 70 metric ton dry mass estimate seems high to me. The original ITS tanker, about twice is big, had a 90 metric ton dry mass. So I would expect the BFS dry mass to be closer to 45 metric tons.

 

  Bob Clark

I wouldn't trust the ITS numbers. But even beyond that, the square cube law may provide some of the difference. The area (thus some of the structural mass) shrinks at a different rate than the volume (thus propellant mass), and so a larger tank doesn't need much more structure.

For example, the modern Atlas V first stage has a mass ratio around 14.5, compared to the huge Saturn V first stage (S-1C), that had a mass ration of around 16.9. Keep in mind advances made in materials since the 60s, and the Saturn V first stage even had fins...Of course they each do different jobs, but a large part of that difference is likely attributable to sheer size.  

[harrisjosh2711]

Newest headline pic-

[mikegarrison]

13 hours ago, tater said:

I can only assume nasa messed with this a little before Apollo. Still, you're talking about a much larger craft with higher thrust, and the engines are mission critical for return.

NASA had a lander simulator. https://crgis.ndc.nasa.gov/historic/Lunar_Excursion_Module_Simulator

But it was primarily for astronaut training. The pilot was supposed to pick a flat spot to land on, which obviated the need to have a lander that could land on non-flat surfaces.

Edited October 16, 2017 by mikegarrison

[kerbiloid]

6 hours ago, Bill Phil said:

But even beyond that, the square cube law may provide some of the difference.

Does the square cube law work for pressurized envelopes?
The envelope required thickness is more or less proportional to the curvature radius for the same pressure/tensile strength.
So, the pressurized envelope mass would grow like ~size³, like its volume.

Edited October 16, 2017 by kerbiloid

[Ultimate Steve]

18 hours ago, Nibb31 said:

Or he's just full of fecal matter. This is reddit we are talking about after all.

That is true for 99% of Reddit. The SpaceX subreddit has extreme moderation protocols and almost everything that is off-topic, rude, or has already been said gets deleted. Probably half of everything I've posted over there has been deleted...

But, yes, that guy could be making stuff up. We'll find out soon, I guess.

[Exoscientist]

3 hours ago, kerbiloid said:

Does the square cube law work for pressurized envelopes?
The envelope required thickness is more or less proportional to the curvature radius for the same pressure/tensile strength.
So, the pressurized envelope mass would grow like ~size³, like its volume.

 That is true for the mass of the propellant tanks that it scales with the size of vehicle. Other components do also such as the mass of the engines. But some do not such as tank insulation which scales more closely to surface area.

 See this report that gives vehicle component scaling relationships:

Mass Estimating Relations.
• Review of iterative design approach
• Mass Estimating Relations (MERs)
• Sample vehicle design analysis
http://spacecraft.ssl.umd.edu/academics/483F09/483F09L13.mass_est/483F09L13.MER.pdf

 By the way, it is interesting that the author, head of the department of aerospace engineering at the University of Maryland, concludes that SSTO's are possible using hydrolox propellant.

  Bob Clark

 

 

 

[Streetwind]

Nobody's arguing "possible". Mount an aerodynamic nose on a Falcon 9 first stage and it can SSTO by itself, with just kerolox fuel. Doubt it's the first ever vehicle capable of this either.

The thing that's worth discussing is "useful", and perhaps also "cost-effective"  

Edited October 16, 2017 by Streetwind

[kerbiloid]

11 minutes ago, Exoscientist said:

http://spacecraft.ssl.umd.edu/academics/483F09/483F09L13.mass_est/483F09L13.MER.pdf

Thanks for the link!

[Racescort666]

On 10/15/2017 at 11:48 AM, _Augustus_ said:

Someone on NSF pointed out that a secret government payload doesn't need FAA clearance to launch, so Zuma is definitely a commercial payload.

All bets are on it either being an internal SpaceX mission, or SpaceIL.

 

The license was filed with the FCC. That being said, defense is largely exempt from other regulatory practices (if it is an NRO flight or some kind of spy mission) but that doesn't necessarily exempt SpaceX from needing to comply with said regulations using their commercial hardware.

[Exoscientist]

21 hours ago, Bill Phil said:

I wouldn't trust the ITS numbers. But even beyond that, the square cube law may provide some of the difference. The area (thus some of the structural mass) shrinks at a different rate than the volume (thus propellant mass), and so a larger tank doesn't need much more structure.

For example, the modern Atlas V first stage has a mass ratio around 14.5, compared to the huge Saturn V first stage (S-1C), that had a mass ration of around 16.9. Keep in mind advances made in materials since the 60s, and the Saturn V first stage even had fins...Of course they each do different jobs, but a large part of that difference is likely attributable to sheer size.  

 

 Here's the description of the original ITS upper stage, both spaceship and tanker versions:

 And here's the description of the BFR spaceship, half size to the ITS version:

 You see the BFR spaceship is about half the listed value for the ITS spaceship.  Actually during the video Musk says the design mass was 75 tons, but the 85 tons was allowing for weight growth. So it is plausible the BFR tanker is half the mass of the ITS version or a little more, ca. 45+ tons.

  Bob Clark

 

Edited October 17, 2017 by Exoscientist

[tater]

Northrop Grumman providing the Zuma payload for customer "government."

[CatastrophicFailure]

Yup, spy bird.  I’ll be sure to give it my opinion when it passes over. But they already know what it is. 

But oh, cool, next Iridium flight out of Vandy will be the first west coast RTLS.  Maybe even a used booster. 

[Bill Phil]

1 hour ago, Exoscientist said:

 

 Here's the description of the original ITS upper stage, both spaceship and tanker versions:

 And here's the description of the BFR spaceship, half size to the ITS version:

 You see the spaceship is about half the listed value for the ITS spaceship.  Actually during the video Musk says the design mass was 75 tons, but the 85 tons was allowing for weight growth. So it is plausible the BFR tanker is half the mass of the ITS version or a little more, ca. 45+ tons.

  Bob Clark

 

I'm not arguing with the listed values. Just saying that I wouldn't trust them (weight growth).

[cubinator]

10 hours ago, Streetwind said:

Nobody's arguing "possible". Mount an aerodynamic nose on a Falcon 9 first stage and it can SSTO by itself, with just kerolox fuel. Doubt it's the first ever vehicle capable of this either.

The thing that's worth discussing is "useful", and perhaps also "cost-effective"  

C'mon, you could send a giant wheel of cheese into orbit on one of those stages!

[tater]

BFS (alone) as an SSTO with even 10t cargo is the USAF's wish come true. Doesn't even need launch clamps, just a blast trench underneath (just to increase lifespan by decreasing wear and tear, it has no such thing on the Moon or Mars).

Seriously. Fuel up, and go. Land at any AFB you will overfly. By the time anyone has the orbital elements, you can be back at base.

[cubinator]

8 hours ago, tater said:

BFS (alone) as an SSTO with even 10t cargo is the USAF's wish come true. Doesn't even need launch clamps, just a blast trench underneath (just to increase lifespan by decreasing wear and tear, it has no such thing on the Moon or Mars).

Seriously. Fuel up, and go. Land at any AFB you will overfly. By the time anyone has the orbital elements, you can be back at base.

I suppose they do have the money to pay for it.

[CatastrophicFailure]

4 hours ago, cubinator said:

I suppose they do have the money to pay for it.

So, they’d finally get their quick-response space “shuttle” they wanted 40 years ago. 

[KSK]

1 hour ago, CatastrophicFailure said:

So, they’d finally get their quick-response space “shuttle” they wanted 40 years ago. 

I'm reminded of some of the original 'Orbiter plus fly-back booster' plans for the Shuttle. Hopefully technology in the form of BFR is finally catching up with aspiration.