totm nov 2023 SpaceX Discussion Thread

[cubinator]

13 minutes ago, zolotiyeruki said:

Hard?  Actually, no.  It just takes beefier equipment.  Really big hydraulic rams, with really big pumps behind them.  I'm reminded of a job I had several years ago, where a large work barge (probably 100x250ft) was next to a big oil platform.  The barge's thrusters kept it quite precisely aligned with the mostly-stationary oil platform, despite the motion of the waves.

I hope that I've misjudged humanity's capacity to build gigantic things!  

[CatastrophicFailure]

1 hour ago, cubinator said:

I hope that I've misjudged humanity's capacity to build gigantic things!  

All the needed components exist as separate pieces: giant, superstrong structures; strong, fast hydraulics; robotics; booster-landing accuracy; massive shock absorbers, etc. What SpaceX needs to do is combine them all together. Which is NOT to say this isn’t a huge engineering challenge, but it’s far easier than conjuring something entirely new up from scratch, like belly-flopping Starship. The more I think about it, the less kooky catching the booster seems.

[StrandedonEarth]

38 minutes ago, CatastrophicFailure said:

The more I think about it, the less kooky catching the booster seems.

Not kooky at all compared to trying to land directly on the launch clamps with centimeter precision.

 

Nice Blaze of Glory sonic boom. When conditions are right nature can do some amazing (or amazingly beautiful) things. But yeah, I can imagine quite a few people thought the vehicle was toast when that happened. Too bad I missed it live (TCB). I wonder if anyone caught some less over-exposed shots of this event, or something that can be enhanced....

Edited May 26, 2021 by StrandedonEarth

[Xd the great]

Would SpaceX test a scaled down "ring catcher" for Superheavy Booster with F9?

[SpaceFace545]

12 minutes ago, Xd the great said:

Would SpaceX test a scaled down "ring catcher" for Superheavy Booster with F9?

They were supposed to test a scaled down BFR on falcon 9 but that didn't happen. Spacex will probably continue their trial and error approach with the full scale starship.

Edited May 27, 2021 by SpaceFace545

[CatastrophicFailure]

39 minutes ago, Xd the great said:

Would SpaceX test a scaled down "ring catcher" for Superheavy Booster with F9?

Unlikely, the HUGE, important difference between SupeeHeavy and F9 (other than, well, size) is that SuperHeavy can hover. 

This really cannot be stated enough, it’s what makes all the difference here.

SuperHeavy can hover, that’s what allows the pinpoint accuracy and zero-ish “touchdown” speed this needs to work. If SH is off a couple meters, it can stop, and then correct (fuel remnant notwithstanding). The real load on the tower should be relatively minor. 

F9, OTOH, has to cut its engine at exactly the right moment to stop just before it hits the deck, and can’t really correct its course in the final moments before touchdown, as such (we saw this, sort of, in the FH core that “aborted” and went shooting off sideways),  so trying to “catch” it is a nonstarter. 
 

Also: Vandy getting some action again. 

 

[cubinator]

Interesting, I might get to see one of those if I'm lucky.

[StrandedonEarth]

18 minutes ago, CatastrophicFailure said:

. Also: Vandy getting some action again. 

 

Why waste margin on a dogleg when there are better options? Besides, it takes pressure off of the Florida range. 

I imagine they’ll probably use the same core for all the launches there

[tater]

 

[JoeSchmuckatelli]

54 minutes ago, CatastrophicFailure said:

is that SuperHeavy can hover

is supposed to be able to hover.

 

Excited to see them try it.

[wumpus]

12 hours ago, JoeSchmuckatelli said:

is supposed to be able to hover.

 

Excited to see them try it.

They've already designed the raptors (although I'm sure they are also a work in progress).  If they can throttle deep enough, SuperHeavy can hover.  Assuming you can turn off arbitrary numbers of the 30+ raptor engines, that should be trivial to achieve.

The other issue is of course maintaining stability.  But compared to a Falcon 9 booster, a SuperHeavy will have considerably more moment of inertia and require far easier timing.  It might take more force to keep it upright, but you have much more time to react.  Making it hover should largely be a function of having enough propellant left in the tanks to hover until caught.

[sevenperforce]

13 hours ago, tater said:

 

That's really interesting. I wonder when they changed that. The most recent official renders showed tiles on the back side of the forward flaps but not on the back side of the aft flaps.

Of course that animation was absolutely incredible.

I wonder where the plasma spillover areas are. 

[RCgothic]

 

 

 

[tater]

 

[RealKerbal3x]

I still think the chance of SN16 flying is low. Any data they could have got from flying SN16 could also have been got from reflying SN15 (with reuse data to boot), and they seem to have decided against that. Plus, SN16 has been sitting there for weeks with no progress (it's still missing the aerodynamic tips for the aft flap housings). 

As far as I can tell they're 100% focused on getting to orbit as soon as possible.

[sh1pman]

2 hours ago, RealKerbal3x said:

As far as I can tell they're 100% focused on getting to orbit as soon as possible.

So, what’s the consensus here, does it count as “orbit” if periapsis stays in the atmosphere the entire flight?

[Beccab]

Just now, sh1pman said:

So, what’s the consensus here, does it count as “orbit” if periapsis stays in the atmosphere the entire flight?

Imo, either use the KSP definition (periapsis outside of the karman line or it's suborbital) or take into account just velocity (if it has orbital velocity it counts as orbital). I'm more for the second personally

[magnemoe]

10 minutes ago, Beccab said:

Imo, either use the KSP definition (periapsis outside of the karman line or it's suborbital) or take into account just velocity (if it has orbital velocity it counts as orbital). I'm more for the second personally

In KSP its not in orbit, neither would it count as first satellite in orbit. But its an trajectory who it would be easy to make into an orbit, however they don't want to risk it ending up stranded in space because some error and falling down an random location, this would be worse than the Chinese stage since starship is larger and design to survive reentry. 

Who brings up an interesting quesion, Musk said it was most likely that SN20 would break up during reentry, now if this happen inside the plasma bubble how will the get telemetry? Could they use starlink from the back?  Do they plan to have an black box who survives? 

[RCgothic]

I think it's fair to say it's a test of an orbital launch system even if it doesn't complete a complete revolution.

The boundary between orbital and suborbital is quite fuzzy.

It's actually quite difficult to stay in space for an entire revolution in an initially circular orbit just above the karman line, but that would definitely be an orbit despite the instability.

Whereas an aerobraking trajectory from lunar return isn't really suborbital, but by strict definition it would be.

The only reason there's a cat fight about it is because SLS fans still wants to claim they got there first and Starship fans also want to be first. But as SN21 and SN22 will probably make more ambitious flights before SLS launches anyway I'm fairly relaxed.

2 minutes ago, magnemoe said:

In KSP its not in orbit, neither would it count as first satellite in orbit. But its an trajectory who it would be easy to make into an orbit, however they don't want to risk it ending up stranded in space because some error and falling down an random location, this would be worse than the Chinese stage since starship is larger and design to survive reentry. 

Who brings up an interesting quesion, Musk said it was most likely that SN20 would break up during reentry, now if this happen inside the plasma bubble how will the get telemetry? Could they use starlink from the back?  Do they plan to have an black box who survives? 

I expect it will be heavily photographed by emplaced assets as it comes down, and that there'll be some sort of black box too.

Edited May 28, 2021 by RCgothic

[tater]

3 hours ago, sh1pman said:

So, what’s the consensus here, does it count as “orbit” if periapsis stays in the atmosphere the entire flight?

Define "in the atmosphere."

ISS needs reboosts. Density is low, but not zero up there.

The existence of detectable atmosphere doesn't really matter. It gets into word parsing at some level. It will certainly not be tested in a stable orbit. Where stable is defined as remaining roughly the same apogee and perigee for multiple orbital periods. Even that is vague as LEO sats all decay.

McDowell has proposed a more rigorous Karman line closer to 80 km for this reason. Generally if both the apogee and perigee drop below 80km, that sat is coming down this orbit.

In short, it's still not well defined, there's nothing that says that orbits can't intersect planets—they're just not stable if they do.

As was said above, it's likely that the people who hate SpaceX will say it doesn't count. Whatever. SpaceX will land one on the Moon, then that won't be a big deal because it has no people on it, so that doesn't count, etc. Goalpost shifting will obviously continue.

[kerbiloid]

Quote

An orbital spaceflight (or orbital flight) is a spaceflight in which a spacecraft is placed on a trajectory where it could remain in space for at least one orbit. To do this around the Earth, it must be on a free trajectory which has an altitude at perigee (altitude at closest approach) around 80 kilometers (50 mi); this is the boundary of space as defined by NASA, the US Air Force and the FAA. To remain in orbit at this altitude requires an orbital speed of ~7.8 km/s. Orbital speed is slower for higher orbits, but attaining them requires greater delta-v.

Quote

 is placed on a trajectory where it could remain in space for at least one orbit

Quote

at least one orbit

So, if the periapsis in below the space boundary, it is not..

Edited May 28, 2021 by kerbiloid

[tater]

We get it, people will have an interest in saying that Starship isn't a thing for as long as possible.

Doesn't matter if it's SN21, SN22, or whichever does a complete orbit, one will eventually. SpaceX has an interest in paying for dev by launching their own sats, so they put it into a Starlink deployment orbit fairly early—that or they add a kick stage for that purpose.

Regardless, when they put in in an orbit that might be 900km x 30km, raising the perigee to make it complete one full orbit would be trivial. If the RCS works at all, it "could" be in orbit. It's hair splitting. Next thing we'll be saying that orbital crew flights don't count if the pilot bailed out of his vehicle.

Edited May 28, 2021 by tater

[sevenperforce]

2 minutes ago, tater said:

It's hair splitting. Next thing we'll be saying that orbital crew flights don't count if the pilot bailed out of his vehicle.

I see what you did there.

[tseitsei89]

IMO you are in orbit if your periapsis is above ground level. It just isn't a stable orbit since air resistance will slow you down but it is an orbit. There is no clear altitude where atmosphere stops slowing you down, it just gets weaker and weaker the higher you go so defining it with some arbitrary periapsis height is...well arbitrary.

Saying you have to complete a full orbit in order to be in orbit is also sketchy. You can put a ship in a 500km x 500km orbit and do a deorbit burn before you complete a full orbit. You clearly were in orbit but you just exited orbit before completing a full circle.

[SpaceFace545]

Why the heck are y'all still having this petty argument about if starship is in orbit or not.