totm nov 2023 SpaceX Discussion Thread

[Ultimate Steve]

3 minutes ago, Deddly said:

The article doesn't mention SpaceX. Aren't they using their own system?

EDIT: The article is five years old.

This was in response to wondering how fast the ISS comms system was in comparison, and the ISS system was not built by SpaceX.

[darthgently]

People amaze me

[JoeSchmuckatelli]

9 hours ago, darthgently said:

People amaze me

Pretty much the theme of my class. 

Ofc - I teach from the Neolithic Revolution to the Modern World... And, yeah

 

We've come a long way since Rock on Stick was cool 

[darthgently]

1 hour ago, JoeSchmuckatelli said:

Pretty much the theme of my class. 

Ofc - I teach from the Neolithic Revolution to the Modern World... And, yeah

 

We've come a long way since Rock on Stick was cool 

Rock on Stick is still cool!  It's all cool! 

Did an ancient person ever stand on one side of a chasm or deep cut ravine that he needed to get across?  Yes.  Undoubtedly. 

Was he pondering the situation while, out of rock-throwing habit and frustration, also throwing rocks to the other side?  Yes, almost certainly.   Hunters throw rocks, especially when stymied.

Did he at some point, out of sheer wishful thinking and fringe brainstorming, imagine somehow being small like a clinging mouse and riding the rock to the other side of the chasm?  Almost certainly at some point in history something very similar occurred at some time and place.  Possibly many times.  But of course the thought was dismissed as silly and pointless.  Which it was at the time.  But even then we could imagine it, and want it.

Now we throw the stick upward, and send the rock, with people inside, into orbit around the entire world we have ever known.  

And then people, us, descendents of the hunter at the chasm, emerge out of the rock into our infinite sky.  Our infinite sky.  And it is not silly.  It's awesome, in the deepest sense

Edited September 13 by darthgently

[Nuke]

then we want to hit rocks with sticks on mars or the moon. and thanks to some smuggled golf clubs and balls it finally happened one day.

[mikegarrison]

On 9/13/2024 at 4:54 AM, darthgently said:

Rock on Stick is still cool!  It's all cool! 

Did an ancient person ever stand on one side of a chasm or deep cut ravine that he needed to get across?  Yes.  Undoubtedly. 

Was he pondering the situation while, out of rock-throwing habit and frustration, also throwing rocks to the other side?  Yes, almost certainly.   Hunters throw rocks, especially when stymied.

Did he at some point, out of sheer wishful thinking and fringe brainstorming, imagine somehow being small like a clinging mouse and riding the rock to the other side of the chasm?  Almost certainly at some point in history something very similar occurred at some time and place.  Possibly many times.  But of course the thought was dismissed as silly and pointless.  Which it was at the time.  But even then we could imagine it, and want it.

Now we throw the stick upward, and send the rock, with people inside, into orbit around the entire world we have ever known.  

And then people, us, descendents of the hunter at the chasm, emerge out of the rock into our infinite sky.  Our infinite sky.  And it is not silly.  It's awesome, in the deepest sense

This is an interesting flight of fancy trying to work "rocks and sticks" into spaceflight, but from experience I can tell you that hunters throw rocks "when frustrated" no more than anyone else does. Probably less, because generally they are trying to be not noticed.

And, of course, rather than imagining "flying on a rock", isn't it more likely that people would imagine being able to fly like the flying things they saw all around them, namely birds and insects?

Edited September 14 by mikegarrison

[CatastrophicFailure]

On 9/9/2024 at 7:05 AM, Terwin said:

I thought the moon has wonky gravity that causes problems for long-term orbits, and that is why we have mars satellites before we have moon satellites.

The wonky gravity is more an annoyance, like a halo orbit it requires a craft to expend fuel to keep a stable orbit. There are some naturally stable low lunar orbits, but they’re inherently limited. It’s not an insurmountable problem at all but there needs to be demand for that comms, and that doesn’t exist just yet. MoonLinks would just be burning fuel for nothing right now. 
 

On 9/9/2024 at 7:09 AM, darthgently said:

Probably.  The lunar mascons are an annoyance but I think between not being too low and newer ion thrusters combined with using solar pressure and such it isn’t hard to maintain a stable orbit for decades.  Not sure though

China is doing it

China’s relay is out at the Lagrange point, IIRC. 

[darthgently]

1 hour ago, mikegarrison said:

This is an interesting flight of fancy trying to work "rocks and sticks" into spaceflight, but from experience I can tell you that hunters throw rocks "when frustrated" no more than anyone else does. Probably less, because generally they are trying to be not noticed.

And, of course, rather than imagining "flying on a rock", isn't it more likely that people would imagine being able to fly like the flying things they saw all around them, namely birds and insects?

This is the battle you choose today.  Amazing

Stanley Kubrick’s early scene of the tossed bone becoming an orbiting craft in 2001: A Space Odyssey was the touchstone image so take it up with him

Edited September 14 by darthgently

[magnemoe]

2 hours ago, darthgently said:

This is the battle you choose today.  Amazing

Stanley Kubrick’s early scene of the tossed bone becoming an orbiting craft in 2001: A Space Odyssey was the touchstone image so take it up with him

This the tossed bone became an spear, then thrown by an spear thrower, an arrow, crossbow bolt then cannons in medieval times, artillery in the 1850s then the  V2 followed by orbital rockets. 
At this stage I say heavy rockets in 2040 will be fully reusable unless launching something very heavy or very hard, I say this is questionable with some starship configurations. 
Tech bros I agree here  http://freefall.purrsia.com/ff3000/fc02997.htm 

Edited September 14 by magnemoe

[darthgently]

 

 

 

[CatastrophicFailure]

On 9/13/2024 at 4:54 AM, darthgently said:

And then people, us, descendents of the hunter at the chasm, emerge out of the rock into our infinite sky.  Our infinite sky.  And it is not silly.  It's awesome, in the deepest sense

Any sufficiently advanced technology is indistinguishable from magick. 
 

23 hours ago, darthgently said:

This is the battle you choose today.  Amazing

Stanley Kubrick’s early scene of the tossed bone becoming an orbiting craft in 2001: A Space Odyssey was the touchstone image so take it up with him

I’m more reminded of a certain scene from History of the World Pt 1… 

[Exoscientist]

Contrary to the criticism that the FAA is singling out SpaceX, they are actually protecting SpaceX.

 From the FAA:

SpaceX's current license authorizing the Starship Flight 4 launch also allows for multiple flights of the same vehicle configuration and mission profile. SpaceX chose to modify both for its proposed Starship Flight 5 launch, which triggered a more in-depth review," agency officials wrote. 
"In addition, SpaceX submitted new information in mid-August detailing how the environmental impact of Flight 5 will cover a larger area than previously reviewed," they added. "This requires the FAA to consult with other agencies." 

 Note mention of a change in “mission profile”. The change to a landing on land compared to an ocean landing is a quite significant change in mission profile. For a landing on land you have to give extra scrutiny to the possibility of an explosion. Angry Astronaut discusses this in his video:

FAA releases vital information about SpaceX Starship!
https://youtube.com/clip/UgkxzdNH9SHX1vbzntoM31LLNxOr_FO3oUS8?si=tgQ9IDcsQY8k6Ejx

The FAA has two sometimes opposing interests. One, they want to preserve public safety, but they also don’t want to reveal proprietary information from a company. Note though proprietary information can be information beneficial to a company. But it can also be information detrimental to the company.

It’s fairly evident a Raptor exploded during the landing burn. But SpaceX does not want to discuss this publicly. Also most people are aware of the fact the Super Heavy exploded after ocean touch down. SpaceX also has not wanted to discuss this publicly. But the possibility of an explosion during a landing catch has to be given serious consideration by the FAA. However, because SpaceX has not wanted to discuss publicly the fact the booster exploded after touchdown the FAA can’t reveal this either.

 

  Bob Clark

[zolotiyeruki]

30 minutes ago, Exoscientist said:

It’s fairly evident a Raptor exploded during the landing burn. But SpaceX does not want to discuss this publicly. Also most people are aware of the fact the Super Heavy exploded after ocean touch down. SpaceX also has not wanted to discuss this publicly. But the possibility of an explosion during a landing catch has to be given serious consideration by the FAA. However, because SpaceX has not wanted to discuss publicly the fact the booster exploded after touchdown the FAA can’t reveal this either.

There's a heavy implication here that SpaceX owes the public this information about exploding engines and stages, and by not divulging it, they are somehow trying to hide it or deceive the public or the FAA. 

I'm not terribly concerned about an explosion during a landing catch.  After all, SpaceX has more incentive than *anybody* to make sure it's safe.  It's their money at stake.  As for the public or the environment?  Meh, the area is cleared anyway, and the only thing they'd be scattering into the environment is steel, water, and CO2.

34 minutes ago, Exoscientist said:

Contrary to the criticism that the FAA is singling out SpaceX, they are actually protecting SpaceX.

Perhaps my reading comprehension is failing me, but I'm not seeing anything in the quote that supports the claim that the FAA is protecting SpaceX (or from what).

[tater]

 

 

[tater]

Success

[tater]

These problems will only get worse if Blue Origin not only starts flying, but tries for the cadence that Bezos desperately needs if Kuiper is to be a thing. BO 100% needs to fly at F9 cadence ASAP if they are to have any hope of getting half the constellation on orbit by their deadline, and the FAA simply cannot cope with the launch cadence they have now, much less any increase.

Perhaps there needs to be a fee structure for launch providers designed to scale the number of FAA compliance people with launch cadence? No fee for up to X launches per year, then above that X cutoff fees to fund however many new employees are required?

[Nuke]

i find it odd that spacex is asking for more regulators rather than less regulations.

[Exoscientist]

Expendable, Starship can do 250 tons to LEO:

 Elon has made news by stating Starship can make unscrewed flights to Mars in 2 years and crewed flights in 4 years. But just stripping off the reusability systems the Starship would have a 200 to 250 ton payload capability and could do single launch flights to Mars now.

  Bob Clark

Edited September 19 by Exoscientist

[Ultimate Steve]

19 minutes ago, Exoscientist said:

unscrewed flights to Mars in 2 years

I mean you do have to have a few screws loose to try going to space at all, so...

19 minutes ago, Exoscientist said:

 Elon has made news by stating Starship can make unscrewed flights to Mars in 2 years and crewed flights in 4 years. But just stripping off the reusability systems the Starship would have a 200 to 250 ton payload capability and could do single launch flights to Mars now.

  Bob Clark

One of the big points of Starship is that it is supposed to be the lander. Stripping off the reusability hardware means you no longer have a lander.

I'm having trouble envisioning a reasonable 250 ton Mars capable manned vehicle, even with ground equipment launched separately. If Starship does the TMI and we assume optimistic numbers (40t dry Starship, propellant is equivalent to LEO payload for a combined number of 250 tons, 3.6km/s to Mars, 382s isp for the burn), then you get 70 tons for the Mars vehicle itself. And that is an unrealistic upper bound.

I'm having even more trouble imagining that anyone could develop a Mars vehicle of any mass before SpaceX gets reusability and refueling working.

Edited September 19 by Ultimate Steve

[Flavio hc16]

2 hours ago, tater said:

These problems will only get worse if Blue Origin not only starts flying, but tries for the cadence that Bezos desperately needs if Kuiper is to be a thing. BO 100% needs to fly at F9 cadence ASAP if they are to have any hope of getting half the constellation on orbit by their deadline, and the FAA simply cannot cope with the launch cadence they have now, much less any increase.

Perhaps there needs to be a fee structure for launch providers designed to scale the number of FAA compliance people with launch cadence? No fee for up to X launches per year, then above that X cutoff fees to fund however many new employees are required?

In theory, it works, but in practice in the long run you risk a Boein 737 Max complacency, where the provider that gives you more money get a lowered scrutiny

[tater]

31 minutes ago, Nuke said:

i find it odd that spacex is asking for more regulators rather than less regulations.

FAA regulations exist to protect public safety. I think SpaceX has no issues with protecting public safety. Their current issues seem to overwhelmingly related to an agency where the spaceflight component is scaled to a national launch cadence that is now much higher.

The first commercial spaceflight in the US was in 1989, but most launches were still government (a few Shuttle flights/year til 2011, plus defense launches). The spike in the late 90s was a bunch of Iridium launches added into the mix. The most launched in 1 month in 1997 was 6 (4 were government). These were planned well in advance, so they could deal with it. We're now pushing 3X the total launches of the odd mid-90s spike, with no sign of a decreasing cadence. new companies joining the fray not only means more launches, but more novel vehicles with the associated risks during test flight campaigns. Heck, even ground testing requires FAA input.

2 minutes ago, Flavio hc16 said:

In theory, it works, but in practice in the long run you risk a Boein 737 Max complacency, where the provider that gives you more money get a lowered scrutiny

I don't think it would work that way—I'm in effect talking about a tax, and it's not like people who pay more tax get lower scrutiny...

[darthgently]

1 hour ago, Nuke said:

i find it odd that spacex is asking for more regulators rather than less regulations.

Pretty sure they aren’t asking for that, just more efficient, and less unnecessary process.

[tater]

9 minutes ago, darthgently said:

Pretty sure they aren’t asking for that, just more efficient, and less unnecessary process.

They specifically say that FAA lacks the resources to deal with the current environment. "Resources" for a gov agency is money, and people. It's a smart political play—just as BO putting their engine factory in AL was—as they are in effect asking for the current FAA Administrator to have more power (larger agency = more power).

[Terwin]

I vaguely remember something about the heat tiles only being needed for earth because the mars atmosphere is so much thinner, so the weight of the heat system might be what is referenced 

[Ultimate Steve]

18 minutes ago, Terwin said:

I vaguely remember something about the heat tiles only being needed for earth because the mars atmosphere is so much thinner, so the weight of the heat system might be what is referenced 

I wouldn't be surprised but I don't think so. From a velocity standpoint at mars you're looking at a 6ish km/s entry. IFT 4 was still melting at 4ish km/s.

Hypersonic heating is a dark art so I can't tell you exactly how it will change, but the gamma value for co2 is 1.3 where 1.4 is typically used for earth. Speed of sound is also significantly lower in co2 so mach numbers will be higher. Temperature and pressure equations for a compressive model depend on mach number and not directly on velocity so those will be significantly higher as mach is often raised to various powers. But hypersonics are a dark art and the temperature of the gas for conduction is only one factor you need to take into account, and probably not the biggest factor as one of the driving factors behind heat shield design is to try to not touch the shocks.

At very high speeds, I do know that heating is suppressed as the energy that would go into heating your ship up instead goes into breaking apart O2 and N2 into O and N, though that means you now have to deal with free, hot monotonic oxygen rubbing up against your heat shield. Will be interesting to see how stuff that is reused hundreds of times evolves to deal with that.

I'm unsure if CO2 is kinder or harsher in the respects of this heat suppression or chemical reactivity, or how other trace elements may or may not pose problems.

Martian heat shield design is a deceptively complex problem, and I only learned the easy version!

All this is moot, however, as you generally want to come back from Mars, requiring a blazing hot Earth entry. Though not that much hotter than a Lunar entry, which they were planning on doing at some point (RIP DearMoon).