totm nov 2023 SpaceX Discussion Thread

[Ultimate Steve]

15 minutes ago, tater said:

 

Also minimizes redundancy, though...

[cubinator]

If you're in the US, keep an eye out for these guys in the evening these next few days. They should be visible. Probably not tonight, though - it's too late, the sun is too far out of the way.

If this test goes well, we should see many more launches like this, though, and might get to see clusters of sats just after launching!

1 minute ago, Ultimate Steve said:

Also minimizes redundancy, though...

I think the redundancy factor in making these sats cheap and en masse makes up for that.

[Ultimate Steve]

2 minutes ago, cubinator said:

If you're in the US, keep an eye out for these guys in the evening these next few days. They should be visible. Probably not tonight, though - it's too late, the sun is too far out of the way.

If this test goes well, we should see many more launches like this, though, and might get to see clusters of sats just after launching!

I think the redundancy factor in making these sats cheap and en masse makes up for that.

I did a whole bunch of math before realizing that my assumption was flawed. I basically found out that the sats may fly over at 11, but orbits are weird, coupled with the rotation of the Earth... I'm going to wait until the swarm is up on a sat tracker website like Heavens Above.

[Brotoro]

SECO 2. Good orbit.

Payload deployment in 15 minutes.

[Ultimate Steve]

I didn't expect them to all release at once!

[Xd the great]

Cards spreading...

[Brotoro]

3 minutes ago, Ultimate Steve said:

I didn't expect them to all release at once!

Yeah, that was unexpected. I wonder how they were all held together and held on the the rocket. Have any diagrams been posted?

[StrandedonEarth]

interesting. So they just released them as en masse and let them drift apart. I assume they were linked together somehow during launch, or did the payload adapter hold them together? It occurs to me they could have used electromagnets to hold them together and then push themselves apart...

Fascinating launch. Heaviest payload yet and they still landed the bird? Block 5 FTW!

[cubinator]

31 minutes ago, Ultimate Steve said:

I did a whole bunch of math before realizing that my assumption was flawed. I basically found out that the sats may fly over at 11, but orbits are weird, coupled with the rotation of the Earth... I'm going to wait until the swarm is up on a sat tracker website like Heavens Above.

That's pretty close, but they're in darkness so no chance of seeing them on this pass.

[CatastrophicFailure]

44 minutes ago, Ultimate Steve said:

did a whole bunch of math before realizing that my assumption was flawed. I basically found out that the sats may fly over at 11, but orbits are weird, coupled with the rotation of the Earth... I'm going to wait until the swarm is up on a sat tracker website like Heavens Above.

Well that kinda answers my question. Was hoping I might get to see them tonight, it’s just past sunset here and the satwatching hours are beginning. Any updates on a real-time orbit track?

[tater]

https://www.starlink.com/

 

 

[Shpaget]

2 hours ago, Ultimate Steve said:

I didn't expect them to all release at once!

Yeah, that's an interesting approach.

I'd probably do something stupid and spin up the second stage to release them one by one.

Or perhaps do something a little less radical and put some springs between them to push them apart.

[tater]

The simpler the mechanism the better, less chance of failure.

[CatastrophicFailure]

32 minutes ago, Shpaget said:

I'd probably do something stupid and spin up the second stage to release them one by one.

Didn’t Musk say they were gonna do exactly this tho? But yeah, did not expect the whole chunk to just go sailing off like that. Hopefully future launches will have a shot where they’re not in blinding sunlight. Like @tater said, simple is better. Who needs a payload rack? The payload is the rack!

[tater]

I was expecting them to serially let go from one another, and spread out that way, vs just PLUNK, and let them drift apart.

[Reactordrone]

2 hours ago, Brotoro said:

Yeah, that was unexpected. I wonder how they were all held together and held on the the rocket. Have any diagrams been posted?

Well they all have these connecting rings so might be held down together or some kind of rotary lock.

40 minutes ago, Shpaget said:

Yeah, that's an interesting approach.

I'd probably do something stupid and spin up the second stage to release them one by one.

Or perhaps do something a little less radical and put some springs between them to push them apart.

Well the second stage was spinning around in yaw, they just didn't let them go one by one.

[tater]

KSP sim done 2 days ago:

 

What's pretty cool is that while these are just a test version (no laser comms between sats on this batch), they just launched almost the entire Iridium constellation (66 sats, plus some spares) in 1 launch.

[Exoscientist]

On 5/17/2019 at 9:14 PM, AVaughan said:

Well if they can refuel in LEO, then they should be able to refuel in a highly elliptical orbit (once they have enough operational tankers).  

From a 250 km LEO lunar transfer is about 3120 m/s, capture to low orbit about 820 m/s, landing 1720 m/s, ascent another 1720 m/s, then Earth return and landing should be another 820 m/s plus around 400 m/s to land. So they need around 8600 m/s.  

So assuming a fully refuelled Starship in LEO, and another fully refuel Starship as tanker (also starting from LEO).   1100 tons fully fueled mass and 75 tons dry mass for both ships.   ISP of 380.  (So the tanker version has 1025 tons of fuel and 10 km/s dV at this point.  The other ship has less because it has a payload).

Burn 2300 m/s with both ships.  That means each ship uses 507 tons of fuel.  Use the tanker to fully refuel the other ship.  That leaves the tanker with 11 tons of fuel, which is 500m/s.  Should be plenty to de-orbit and land.   

At this point a lunar landing and return needs about 6300 m/s.  That means the non-fuel mass of the lunar lander starship + payload can be a little over 200 tons, so on this sort of mission profile Starship can land (and return to earth) around 125 tons of payload.  Plenty of mass for a useful mission.

(dV numbers from an online RO/RSS dV chart, which might be wrong.  Calculations using an online rocket equation calculator plus windows calculator.  Quite possible I entered the wrong number somewhere.  An earlier version of this calculation assumed refuelling in elliptical Lunar orbit, which might need too many refuelling flights to be practical.  I'll leave it below). 

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From an elliptical Lunar orbit landing is about 2400 km/s, ascent another 2400m/s, then Earth return and landing should be about 500 m/s or so. So they need around 5500 m/s.  

Using a lot of tankers to refuel in elliptical lunar orbit, a starship with a dry mass of 75 tons with a payload of 175 tons (and returning that payload to earth to keep calculations simpler), a fully fuelled mass of 1100 tons, ISP of 3800, that looks like a dV of 5517 m/s.  That is definitely a useful payload capacity, but probably too many tanker flights to be practical.

 

 I like your calculation. I noticed you gave a dry mass for the BFR Starship, which is the version of the BFR upper stage with the passenger quarters for 100 colonists on a Mars flight.. But you did not give a dry mass for the tanker, which instead has just a big empty fairing in that space

 What do you estimate the dry mass of the tanker version of the upper stage to be? What do you estimate the delta-v of the empty tanker upper stage to be?

  Bob Clark

[Xd the great]

3 hours ago, Exoscientist said:

 

 I like your calculation. I noticed you gave a dry mass for the BFR Starship, which is the version of the BFR upper stage with the passenger quarters for 100 colonists on a Mars flight.. But you did not give a dry mass for the tanker, which instead has just a big empty fairing in that space

 What do you estimate the dry mass of the tanker version of the upper stage to be? What do you estimate the delta-v of the empty tanker upper stage to be?

  Bob Clark

I think they will stuff a BIG FUEL TANK in the location of the fairing. So what, 150 tons of propellant?

[Spaceception]

9 hours ago, insert_name said:

Not quite, still have a coast phase and engine relight, followed by satellite deployment

Well I meant it just got to orbit but glad to wake up to a mission success

Edited May 24, 2019 by Spaceception

[magnemoe]

39 minutes ago, Xd the great said:

I think they will stuff a BIG FUEL TANK in the location of the fairing. So what, 150 tons of propellant?

Yes, that makes some sense. You need to pipe so it can be filled by the refilling mechanism, this way it can also be drained by it. 

[tater]

[tater]

A lawyer friend was texting me at lunch time. He was reading the SpaceX complaint about the USAF contracting they just submitted. He says complaints don't need exceptional lawyering, but this one seems to be pretty decent in that regard, and is very well done (according to him). It's harsh, and claims are backed up. The fact that they rate risk (which includes schedule risk) as worse for SpaceX, which has existing LVs that can meet most all launch cases required, when literally none of the awarded rockets even exist is pretty stunning.

 

[sh1pman]

35 minutes ago, tater said:

A lawyer friend was texting me at lunch time. He was reading the SpaceX complaint about the USAF contracting they just submitted. He says complaints don't need exceptional lawyering, but this one seems to be pretty decent in that regard, and is very well done (according to him). It's harsh, and claims are backed up. The fact that they rate risk (which includes schedule risk) as worse for SpaceX, which has existing LVs that can meet most all launch cases required, when literally none of the awarded rockets even exist is pretty stunning.

Maybe USAF realized that SpaceX is becoming too big and powerful with their cheap reusable rockets, and soon there will be no other launch provider on the market. So they helped other providers to stay afloat.

[tater]

40 minutes ago, sh1pman said:

Maybe USAF realized that SpaceX is becoming too big and powerful with their cheap reusable rockets, and soon there will be no other launch provider on the market. So they helped other providers to stay afloat.

They should have then specifically included that as a goal, transparently if that is the case. You'd think they'd then keep ULA out, too, it's not like LockMart and Boeing are wallflowers who never get asked to dance by the AF.