totm nov 2023 SpaceX Discussion Thread

[_Augustus_]

12 hours ago, tater said:

Some info on the TESS spacecraft that SpaceX is launching next week

I recently attended a lecture on TESS. A couple interesting things you might not know about it:

• TESS' cameras are little more than very high-end telephoto lenses. They're not particularly big (only 5" aperture) and use only lenses - something seldom seen nowadays on spacecraft, as any lens-based system above about 8" or so is extremely costly, gets heavy fast, and is prone to thermal expansion and other issues.
• Due to limits on the data it can transmit, TESS doesn't have particularly high-resolution CCDs. As a result, each pixel is something like half an arcminute in size - about as big as Jupiter in the sky. This means that if multiple stars brighter than magnitude 12 are within half an arcminute of each other (e.g. a cluster or binary), TESS cannot actually tell which star is experiencing a transit nor get any meaningful data about said transit.
• The orientation of TESS' cameras mean that for the entire survey a 24-degree area around the celestial pole it's currently aimed at (first the north and then south pole) will be in the view of one of the cameras. As a result, significantly more planets and more long-period ones will probably be detected in those regions of the sky, since TESS will be looking at them all the time.
• Because the Falcon 9 is incredibly overpowered for this mission, it may get to RTLS - we'll see......

 

 

1 hour ago, Nightfury said:

Does TESS have RW's or uses it fuel? Turning it so many times would be pretty expensive

Reaction wheels. RCS thrusters' exhaust could get on the optics.

Edited April 5, 2018 by _Augustus_

[tater]

 

[CatastrophicFailure]

Bout time we get a proper landing! I’m going into withdrawals, here! 

[DAL59]

All those exoplanets we've found- remember half of them were just in a tiny patch of the sky that kepler looked at.  So there probably many more nearby exoplanets than we've seen in the kepler data so far. HYPE

Also, first landing in a while HYPE

Can anyone explain what Jonbar hinges are though?

[Wjolcz]

2 hours ago, tater said:

 

So I guess this means they will be retrieving all the non-Block 5 cores to LZ-1 because they can fly them back there and the ones that would normally land on the barge will be thrown into the sea (until B5 is flying)?

Edited April 5, 2018 by Wjolcz

[CatastrophicFailure]

5 minutes ago, Wjolcz said:

So I guess this means they will be retrieving all the non-Block 5 cores to LZ-1 because they can fly them back there and the ones that would normally land on the barge will be thrown into the sea (until B5 is flying)?

They’re trying to go through their supply of old boosters. Pre-Block 5 boosters can only be reused once, or at least that’s all they’re trying with them, so TESS’s booster, being brand new, will be recovered for one more re-use. The existing stock of used boosters will probably be cycled through and thrown away until they’re all gone, to make room for the new B5’s that should last “indefinitely” with refurb. 

[_Augustus_]

6 hours ago, DAL59 said:

All those exoplanets we've found- remember half of them were just in a tiny patch of the sky that kepler looked at.  So there probably many more nearby exoplanets than we've seen in the kepler data so far. HYPE

Also, first landing in a while HYPE

Can anyone explain what Jonbar hinges are though?

TESS is severely limited in the actual number of planets it can reliably detect. It is not a true space observatory like Kepler, nor does it have the same level of funding or attention as Kepler. It's designed to detect as many possible transits as it can, particularly around nearby stars, so ground observatories or other space telescopes can confirm them. That's all.

[DAL59]

18 minutes ago, _Augustus_ said:

That's all.

That's all?!?!??? Wow, how disappointing /s

 

[sh1pman]

8 hours ago, DAL59 said:

That's all?!?!??? Wow, how disappointing /s

 

Still more useful than SLS 

[Wjolcz]

A lot of people seems to be rather critical when talking about BFR. I understand that because it still hasn't been built, nor is it flying, but to me it seems like SpaceX is taking this very seriously considering that their first BFR (ITS) was described only by "it will carry 300 tonnes to Mars" and not much else. Scaling it down and providing more details about refuelling makes it seem way more plausible than previously. Especially taking into consideration that the ship will be more or less the size of shuttle's orange tank. This kind of thing was already built, just not with compisites. And even if it's not 150t to LEO but instead 100t +full reusability it's a pretty damn good score to me. Anyway, all I'm saying is I will be excited when it flies either way. Even if it carries less than it was intended to.

Just some of my rambling.

Edited April 6, 2018 by Wjolcz

[PB666]

1 minute ago, Wjolcz said:

A lot of people seems to be rather critical when talking about BFR. I understand that because it still hasn't been built, nor is it flying, but to me it seems like SpaceX is taking this very seriously considering that their first BFR (ITS) was described only by "it will carry 300 tonnes to Mars" and not much else. Scaling it down and providing more details about refuelling makes it seem way more plausible than previously. Especially taking into consideration that the ship will be more or less the size of shuttle orange tank. This kind of thing was already built, just not with compisites. And even if it's not 150t to LEO but instead 100t +full reusability it's a pretty damn good score to me. Anyway, all I'm saying is I will be excited when it flies either way. Even if it carries less than it was intended to.

Anyway, just some of my rambling.

Well you can compare BFR with other unbuilt space-craft like SLS . . .its like comparing imaginary apples with imaginary oranges.

The problem occurs when you try to compare an imaginary system with one that actually exists. Historical analysis says that this rarely is a fair comparison.

Then there is the fuzzy zone, like SpaceX claiming that it can place 63 ton of FH PL into LEO on a completely recycled rocket . (Which I think they mean on the B5 version of F9, which technically is not a thing yet).

[Wjolcz]

2 minutes ago, PB666 said:

Well you can compare BFR with other unbuilt space-craft like SLS . . .its like comparing imaginary apples with imaginary oranges.

The problem occurs when you try to compare an imaginary system with one that actually exists. Historical analysis says that this rarely is a fair comparison.

Then there is the fuzzy zone, like SpaceX claiming that it can place 63 ton of FH PL into LEO on a completely recycled rocket . (Which I think they mean on the B5 version of F9, which technically is not a thing yet).

Fully recycled? I thought the second stage wasn't going to be reusable?

[tater]

 

[wumpus]

3 hours ago, PB666 said:

Well you can compare BFR with other unbuilt space-craft like SLS . . .its like comparing imaginary apples with imaginary oranges.

The problem occurs when you try to compare an imaginary system with one that actually exists. Historical analysis says that this rarely is a fair comparison.

Then there is the fuzzy zone, like SpaceX claiming that it can place 63 ton of FH PL into LEO on a completely recycled rocket . (Which I think they mean on the B5 version of F9, which technically is not a thing yet).

Except that plenty of parts of BFR and SLS are well known, allowing a certain amount of comparison:

We know the original flight characteristics of the SLS engines because they've flow before (mostly in the shuttle).  Granted, after sufficient senatorial meddling the rocket already has changed significantly and will likely continue to mutate until (or if) it flies.

The BFR's Raptor engine has undergone plenty of testing and has become a known thing.  The lower stage of the BRF is largely a scaled up Falcon 9 lower stage and is known within "Kerbal levels".  Unfortunately the upper stage (fairing, and any third stages) are completely unknown and would remain untested and malleable even if Elon Musk gave everyone access to the engineering data.

So you can argue a lot about each rocket.  Unfortunately the things you can't calculate accurate information about are things like "tonnage to orbit" and "cost of said tonnage", which makes most of the discussion here pointless (except to argue that Rocket labs can likely deliver raw payload cheaper to orbit cheaper (per kg) than SLS.  Because that simply isn't a SLS design goal).

[magnemoe]

15 hours ago, DAL59 said:

That's all?!?!??? Wow, how disappointing /s

 

Its an tripwire system only, telling you here it might be is something interesting however it cover 90% of the sky. 
Now point something serious at target. 
And yes it probably get mission extension if work decently 

[Kr0noZ]

Well, it's basically a survey telescope to spot targets for closer analysis by better telescopes (for which telescope time is limited and therefore expensive).

[CatastrophicFailure]

Looks like no RTLS for TESS, but at least it’s still a recovery! 

Oh, and Bangabandhu (Block 5) will be a drone ship recovery too.

Looking at the chunk of sky this thing will cover, it seems to be everything but near the ecliptic. Anyone know the why of that?

Edited April 6, 2018 by CatastrophicFailure

[sevenperforce]

9 hours ago, PB666 said:

Then there is the fuzzy zone, like SpaceX claiming that it can place 63 ton of FH PL into LEO on a completely recycled rocket . (Which I think they mean on the B5 version of F9, which technically is not a thing yet).

SpaceX has never claimed it can place 63 tonnes of payload into LEO with all-core recovery; that's the expendable payload.

Or do you mean a reused core and reused boosters? Because, yes, they'd need an upgraded PAF, but that's not a meaningful modification.

63 tonnes is Block 4, I think.

[PB666]

3 hours ago, sevenperforce said:

SpaceX has never claimed it can place 63 tonnes of payload into LEO with all-core recovery; that's the expendable payload.

Or do you mean a reused core and reused boosters? Because, yes, they'd need an upgraded PAF, but that's not a meaningful modification.

63 tonnes is Block 4, I think.

That is very doubtful, but since they dont have a purchaser at the moment for 63 tons we may never know. 

[tater]

The LEO payload is necessarily mostly propellant left over in stage 2. A Delta IV 5m upper stage (DCSS) is about the same size as the fairing, and masses 34 tons. So basically a payload that is mostly propellant, and utterly fills the fairing is nothing like 60 tons.

[Ultimate Steve]

3 minutes ago, tater said:

The LEO payload is necessarily mostly propellant left over in stage 2. A Delta IV 5m upper stage (DCSS) is about the same size as the fairing, and masses 34 tons. So basically a payload that is mostly propellant, and utterly fills the fairing is nothing like 60 tons.

Although hydrogen isn't that dense. But agreed, the F9/FH fairing is a bit small. I don't think we'll ever see a LEO payload anywhere near 62t, the extra capability is primarily for BLEO applications (although there is the aforementioned isp problem, which isn't really that much of a problem).

[tater]

32 minutes ago, Ultimate Steve said:

Although hydrogen isn't that dense.

Yeah, but anyone wanting a mass-limited payload is likely putting props in orbit, and if you're doing an upper stage... cryo is what they likely want because of the I_sp.

Wonder how tall a Falcon fairing could be.

 

[PB666]

12 hours ago, tater said:

Yeah, but anyone wanting a mass-limited payload is likely putting props in orbit, and if you're doing an upper stage... cryo is what they likely want because of the I_sp.

Wonder how tall a Falcon fairing could be.

 

Which basically proves my point, it aint real and shouldnt be treated as real until it gets to space, However, spaceX says they are willing to accommodate the customer on the second stage adaptations. . . .you buy we fly. So i assume that fairing modifications are in play. All the form based risks occur around max Q which is a minute before s1/2 booster sep. So they have alot of steering capacity in27 gimbled engines. So controlling the crafts Pl aero should not be a high fail mode. The problem is time required to make new fairings,

Right now spaceX has only 4 takers on FH, but the list of F9 contracts grows by about 10 per minute month

Edited April 7, 2018 by PB666

[tater]

3 hours ago, PB666 said:

Right now spaceX has only 4 takers on FH, but the list of F9 contracts grows by about 10 per minute month

They are likely going to force FH on people at some point, IMO. FH will be used to reduce expendable launches. They'll have to figure out the economics of reuse, then I could see them upping the price to expend a booster, since there will be the cost of manufacturing it, but there is also the opportunity cost of lost future revenue from recovered launches.

I can see them altering the fairing, but substantial changes would also require changes to the TEL, which seems unlikely to me.

[PB666]

15 minutes ago, tater said:

They are likely going to force FH on people at some point, IMO. FH will be used to reduce expendable launches. They'll have to figure out the economics of reuse, then I could see them upping the price to expend a booster, since there will be the cost of manufacturing it, but there is also the opportunity cost of lost future revenue from recovered launches.

I can see them altering the fairing, but substantial changes would also require changes to the TEL, which seems unlikely to me.

Its all wrapped up in demand. Who really wants something 62 tons in LEO . . . . .someone who has a RL10b2 attached to something else with 35 tons of liquid oxygen and 5 tons of hydrogen. Before we can even talk about the fairing we have to talk about the fact that SpaceX has no ability to pump or store hydrogen or deal with the problems that it creates.

35 tons @ 1.141 kg/cubi meter = 31 cubic meter
5 tons @ 0.071 kg/cubic meter = 71 cubic meter
102 cubic meter + volume of container ~120 cubic meter.
 

SpaceX - "13.1 meters . . high and 5.2 meters . .in diameter" ~ 200 cubic meters. (5/2 = 2.5 :  2.5^2 = 6.25: 6.25 x pi = 19.634 :x11 = 215

So there is enough volume in the fairing to store the fuel. However if you have an RL10b-2 engine on the bottom then you have to subtract 4 meters ~ 140 cubic meters.

If you had something reasonably cone shaped it could fit into the fairing that they have but how would you deal with filling the gases?