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SpaceX Falcon Missions Section / Re: SpaceX F9 : Starlink group 6-99 : KSC LC-39A : 17 December 2025 (13:42 UTC)

« Last post by zubenelgenubi on Today at 11:35 pm »

SpaceX countdown clock is currently T-0 17 December 12:19:00 UTC, window opening.

https://www.spacex.com/launches/sl-6-99
New SpaceX T-0 13:42:10 UTC = 8:42:10 am EST
Backup Launch Opportunity #6   
Launch: 2025-12-17 13:42:10 UTC.
Deploy: 2025-12-17 14:47:21.400 UTC.
Launch window: 2025-12-17 13:42:10 UTC to 2025-12-17 13:43:49 UTC.

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Advanced Concepts / Re: Can AI-Data-Centers-in-Space Serve As Sunshade to Terraform Venus?

« Last post by Vultur on Today at 11:32 pm »

Not sure I would trust it, but FWIW, grok came up with 78 million tons for metallic asteroid to produce area 100 million km^2 at a thickness of 50–100 nm. I don't think this fully shades planet but might be enough for substantial cooling.

That's mathematically correct*, but IDK if it's workable. 50-100nm is a very, very thin foil. That's less than the wavelength of visible light (400-750nm), would it even block light?

Also, making an asteroid into that hyperthin film sounds.. really difficult.

Also, a hyperthin iron film isn't a solar panel, so you wouldn't get to do anything with the solar power. It would be a solar sail though, so station keeping would be tricky!

*100 million km^2 (10^8 km^2 = 10^14 m^2) area at 100 nm (10^-7 m) thickness is 10^7 m^3. 7.8 tons/m^3 is about the density of iron.


--

I don't know where those numbers for moving asteroids come from, but I'd strongly disagree with some of the assumptions, especially on propulsion.

 Xenon propellant? Starlink has already gone to cheaper propellants, xenon is just too expensive at scale.
 
I don't see the advantage of VASIMR for this application either.

Nuclear thermal/electric (Isp >10,000 s);

 electric, fine, but no way nuclear thermal is getting 10,000s Isp! Solid core is probably limited to 800-900ish; a nuclear lightbulb might give you 1500 or so?; an open cycle gas core (insanely expensive) maybe 3000?

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Advanced Concepts / Re: Can AI-Data-Centers-in-Space Lead Us Toward Sunshade to Terraform Venus?

« Last post by Bob Shaw on Today at 11:14 pm »

If we’re pushing the limits, then what we really want is matter transmitter technology which would perform two tasks. Firstly, to send CO2 from Venus to Mars, the Moon and Mercury and to give them all dense atmospheres. These should last for thousands of years but will require replenishment - Venus will have enough excess atmosphere for a long time. The second use would be to either send water from the Ice Giants or their oceanic satellites to the other three bodies. Venus wouldn’t be terraformed itself until late in the process but would be a source of oxygen and carbon for the rest of the inner Solar System. Obviously, matter transmission would require command of quantum technologies (probably powered by Handwavium 432 - Dilithium wouldn’t have the energy density).

Oh, if only Mr Birch was still with us…

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Historical Spaceflight / Re: Cape Canaveral Space Force Museum

« Last post by Proponent on Today at 11:03 pm »

I have not been to Atlanta in a very long time.  I suppose the Titan I along I-75 has also decayed and is gone?

You're probably talking about the Titan in Cordele GA, 2-3 hours south of Atlanta.  It's still there as far as I know, but I haven't laid my own eyes on it in a year or two.

Google Earth has a view of it dated 26 February of this year.

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Advanced Concepts / Re: Can AI-Data-Centers-in-Space Serve As Sunshade to Terraform Venus?

« Last post by crandles57 on Today at 11:01 pm »

And putting a satellite in orbit around Venus (when launching from Earth) is at least five times as expensive putting a satellite in Low Earth Orbit.

We would need to bombard Venus with a lot of large comets for the/some water. Maybe the impacts throw off some of the CO2? However to keep the water liquid in order to dissolve probably also fairly insignificant amounts of CO2 we need to reduce temperature below boiling point but that might be quite high under Venus level of pressure? Anyway to get some temperature reduction we also find some metallic asteroids to steer into Sun Venus L1 point while extruding the metal(s) into large thin sheets. Not sure about how to source hydrogen to make some water and/or some extreme alcohols (like methanetetrol / orthocarbonic acid?), but maybe some more asteroids can help.

Sun Venus L1 point is ~1 million km from Venus compared to 108M km to the sun
Sun's diameter of about 1.4 million km is roughly 115 times greater than Venus's diameter

Not sure I would trust it, but FWIW, grok came up with 78 million tons for metallic asteroid to produce area 100 million km^2 at a thickness of 50–100 nm. I don't think this fully shades planet but might be enough for substantial cooling.

As for what we might be able to steer:

Technology Level
Max Asteroid Size/Mass
Max Comet Size/Mass
Delta-V Example
Propulsion/Method
Notes/Sources

Current (2020s tech, e.g., ARM/KISS baselines)
7-10m diameter
500-1,300 tons
5m diameter
100-500 tons (theoretical; no missions)
0.1-1 km/s (rendezvous + return)
SEP (40-150 kW, xenon ion thrusters, Isp ~3,000-5,000 s); robotic capture (e.g., inflatable bag)
Focus on near-Earth objects (NEOs) with Earth-like orbits (low delta-v ~170 m/s for return). ~28:1 mass amplification (spacecraft returns 28x its mass). Comets harder due to ~10-20 km/s excess velocity. Feasible launch: Single Falcon Heavy/Atlas V. 

Near-Future (2030s-2040s, advanced SEP/ISRU)
20-50m diameter
10,000-200,000 tons
10-20m diameter
1,000-10,000 tons (speculative)
0.2-1 km/s per cycle (cycler maintenance)
VASIMR/SEP (high-thrust plasma, Isp ~10,000 s); gravity tractor for fine adjustments; ISRU for on-object propellant
Proposals for cycler insertion (e.g., 1,000-ton asteroid). For 15,000-ton object, ~35 tons propellant per 230 m/s correction. Larger sizes via multi-stage missions or nuclear electric propulsion. Comets possible if intercepted early. 



Far-Future/Speculative (2050+, e.g., fusion/nuclear)
100-500m diameter
1-100 million tons
50-200m diameter
100,000-10 million tons
1-5 km/s (major orbit changes)
Nuclear thermal/electric (Isp >10,000 s); mass drivers (eject material for thrust); swarm robotics
Theoretical for massive shielding (e.g., 370m NEO for natural path-crossing). Full cycler networks possible, but upfront costs immense (trillions). Comets viable for outer-system sourcing. Risks: Political/ethical (e.g., Earth intercept fears). 

Yes it is looking like beyond the top end of "Far-Future/Speculative" ! 

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Blue Origin / Re: Blue Origin's BE-7 engine

« Last post by Brigantine on Today at 10:58 pm »

There was a render (of dubious origin, but seemingly plausible) of a GS3 with I calculated 40 tons of prop and a single BE-7. That's over an hour of burn time. Generally Oberth doesn't matter much because mission planners simply don't push it that far?

It's possible that "GS3" is more of a single-use space tug than a rocket stage, that can last weeks in space and split the burn over many orbits and then help with lunar capture. I guess even if it could only last 24 or 48 hours you could still do several apogee raise maneuvers before TLI.

Do you think this is real?
<image>

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Space Science Coverage / Re: NASA Dragonfly Mission to Titan

« Last post by Fequalsma on Today at 10:54 pm »

The NNSI?  NASA New Start Inflation Index at:
     https://www.nasa.gov/ocfo/ppc-corner/ppc-models-tools/

There is actually an inflation calculator for aerospace. It runs a bit higher than the general inflation rate.

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Historical Spaceflight / Re: Cape Canaveral Space Force Museum

« Last post by ChrisC on Today at 10:53 pm »

Those were on Twitter. He posted other stuff on LinkedIn, but LinkedIn is a pain to extract photos from. And you also have to be a member of both of those places to access them.

Ditto for Twitter ... not only do you NOT have to be a member to view, but if you just post the URL/link here, the NSF forum software automatically embeds it!  And now you know how all of us been posting those fancy Twitter embeds   All we do is post the URL to the post, with one twist: you have to replace "x.com" with "twitter.com", and then the NSF embedder does its thing.  I've done this below with one of the tweets you posted above -- you see all sorts of content below, but all I did was post the twitter.com URL!  Blame Elon.

If you are trying to look at an X.com post, they do indeed make it hard to do without an account (again blame Elon, as all this broke shortly after he stepped in).  But it is possible, with what are called "Nitter" repeaters.  You take the "x.com" and replace it with "twiiit.com" (that's with three letter i's), and it will automatically forward you to the nitter instance that's currently working.  Weird the first time you do it, and then soon it becomes natural.  No question that it's a pain, but at least you don't have to get a Twitter account.

Yes I suddenly had to become an expert in this in Summer 2023 when the big guy smashed up Twitter.  It's all a great big pain, especially the first time you deal with it, but it does work.  And of course yes there is valuable discourse going on in Twitter ...

Twitter embed example follows.

https://twitter.com/James_W_Draper/status/2000236077999857748

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Advanced Concepts / Re: Can AI-Data-Centers-in-Space Serve As Sunshade to Terraform Venus?

« Last post by Vultur on Today at 10:43 pm »

Alright, so we're creating a massive gradient/imbalance with lots of O2 and combustible carbon.

But we have large coal deposits and oil deposits underground here on Earth, that don't combust since they're underground.

So maybe we can somehow produce strata that we can bury and cut off from atmospheric contact.

I'm not saying its physically impossible. Just insanely hard. Probably much harder than terraforming Mars or building a ton of space habitats.

O'Neill colony is more exposed to meteoroids, solar & cosmic radiation, flares, etc.
Air leaks could easily happen.
And who knows, maybe even structural fatigue/failure?
Planets are bigger, more buffered, more stable. Planets are natural.

If you can do this scale of space engineering, you can give the O'Neill colony a shield that is as good or better than Earth's atmosphere. (There are also smaller scale ideas, before a full scale O'Neill colony, that orbit low enough to be inside Earth's magnetosphere - like Kalpana One. This is something that can be done piece by piece, whereas terraforming is more "all at once to get any benefit".)

Air leaks are effectively irrelevant on this scale. There's just so much air, and it can't escape faster than the speed of sound.

Planets are certainly larger, but you can also build *more* space habitats. You can also live in each one as it's built, while terraforming doesn't provide any habitable space until it's more or less done.

As for natural, I don't think terraforming is any more natural than building space habitats.

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Advanced Concepts / Re: How Can We Have NTR SSTO?

« Last post by sanman on Today at 10:41 pm »

Alright - back to fission again. I know you guys will feel I'm flogging the dead horse, but here's another idea to consider:



So madame is pointing to irregular shaped nuclei (this one happens to be dumbbell shaped)

If we have something like a dumbbell-shaped nuclei, then it offers the possibility of achieving a cleaner break in the weaker middle bridge-point, instead of breaking it apart like a pinata and spraying stuff (neutrons) all over the place.

We get fission fragments that are heavier but also likely more stable.
Beryllium-10 is obviously quite light, and so there isn't a whole lot more decay chain its products can undergo. The resulting helium nuclei (aka. alpha particles) are obviously going to be maximally stable.
These alpha fragments are also charged, which makes it easier to harvest their resulting energy, just as the aneutronic fusion fans like to do.
Fine, you're getting a couple of neutrons released along with those 2 larger alpha fragments, but that can be worth it given how much energy you're getting out of those alphas.

Here we can afford to have our nuclear fission products as our direct exhaust stream, albeit with overly high Isp.
So we no longer have the problem of 'working fluid' and heat transfer limitation which limits thrust.
Our overly-fast high-Isp fission products can perhaps be used to augment the Isp of some heavier chemical propellant exhaust.

Even if Be-10 doesn't work out, there may be other irregular-shaped nuclear isomers out there which might have useful fission characteristics that we could usefully exploit, perhaps even for propulsive purposes.

Even if it costs us energy to make exotic irregular-shaped nuclei like this, we can still make it here on the ground for subsequent use during flight, just like we do with so many other rocket fuels.


Maybe proton-spallation could work to break/fission our Be-10 dumbbells, by snatching a neutron or two from the dumbbell bridge which holds the nucleus together. You'd probably want to tune your proton spallation energy to be just enough to break the bridge, to avoid unnecessary neutron release from pinata-breakage.
There are newer medical cyclotrons and laser-driven proton accelerators which accelerate protons, while not being ridiculously large.