[the vertical launch approach]

Just to confirm my intuition I just did a test in ksp. I built a simple two stage rocket with about 5000 m/s delta v with fairly low twr.

First launch was directly upwards and it arrived at the edge of kerbin's soi with a speed of 856m/s.

The second launch did a conventional gravity turn before burning parallel to the surface. That one arrived at the soi with 2000m/s

So it seems clear that the gravity losses for burning directly up are pretty substantial.

[Antimatter Propulsion.. From Earth To Mars Only Requires Milligrams?!]

On 3/9/2024 at 10:58 PM, Nuke said:

points at the state of fusion. if we cant contain deuterium for long enough to fuse what makes you think were ready to be storing antimatter?

Not saying it would be easy but antimatter at 4k would be more likely to stay put than plasma at 150,000,000 k. Or at least be a very different problem.

[SpaceX Discussion Thread]

I like this new euphemism for exploded

"one engine failed energetically"

[For Questions That Don't Merit Their Own Thread]

Where are upper stages launched into editorial orbits disposed of? The plane change delta v for a launch from kourou for example is going to be too large to allow disposal in the usual south Pacific graveyard. Do the stages aim for the equatorial Pacific and hope not too hit anything?

[Fun Fact Thread! (previously fun fact for the day, not limited to 1 per day anymore.)]

TIL that the British navy no longer issues a rum reason, but sailors are allowed to purchase up to 1.5 pints of beer a day

[Alarm Clock Mod [1.2.0]]

I'm seeing an issue where if I use teh x button to remove a maneuvre node alarm from the list it removesa random slection of alarms from the list

[Kerbal Life-Support System (KLSS) [v0.7.0 for KSP2 0.2.1]]

I have discovered the acceleration rate the bug occurs at depends on the whether you have Even Better Time Warp enabld. With it enabled it kicks in at 10,000X, without it it kicks in at 100,000x

Ok, a proper bug Report
Relevant other mods - Even Better Time Warp

To reproduce

Create a ship consisting of a 3-px gumbal capsule, with two kerbals inside, recycler enabled and set to maximum
For power I used the Sm size uranium reactor and I provided additional food

Launch

Go to just below the critical warp value (1,000x or 10,000 depending on event better time warp). Observe that, as expected, o2 and h20 do not drop.
Increase warp 1 notch - o2 and h20 start dropping rapidly

[Kerbal Life-Support System (KLSS) [v0.7.0 for KSP2 0.2.1]]

Great to see sophisticated mods starting to appear.

Is it a know issue that above 1000X timewarp the receycler matchs starts failing an dresoureces that should be infinite start dropping?

[Overview of all AI, not just LLMs]

To be fair the natural intelligence does require a support system that requires more than just the 20 watts. For the average USAian it comes to just less than 10kW.

[SpaceX Discussion Thread]

2 hours ago, Meecrob said:

Fair enough, I'll concede that you can make any company go bankrupt if you try.  The previous trajectory of SpaceX does not mean their future trajectory will be the same. They could drop the ball at any time hypothetically.

Thanks for keeping me honest, lol. We have enough SpaceX fanboys up in here hahahaha!

A paywalled article on Bloomberg suggests that spacex employees are going to be offered a deal to sell their shares at a total company valuation of 175 billion, so going bankrupt imminently seems unlikely.

[For Questions That Don't Merit Their Own Thread]

The Vis-viva equation https://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://en.m.wikipedia.org/wiki/Vis-viva_equation&ved=2ahUKEwjNga-h4NeCAxV0VUEAHWH3B_oQmhN6BAgXEAI&usg=AOvVaw3liegRUJSyyy2Os4MBYXOf

will get you almost everything you might want. E.g. to calculate the DV to go from a 100km orbit to a 200 km orbit you would use the equation to calculate your velocity for the 100km orbit, again to calculate the velocity for the 100x200 when the craft is at 100 orbit. The difference is the DV for the first burn. Repeat for the 200km orbit for the second burn.

[When to do Oberth Maneuver and when not?]

What you are taking about is called a bi-eliptic transfer.

https://en.m.wikipedia.org/wiki/Bi-elliptic_transfer

As the article explains how f the ratio between the radius of the starting or it is less than 11 it is always better to do a hohmann transfer. If it is greater than 16 it is better to do a bi-eliptic transfer.

That is for coplanar orbits, if you are changing inclination then an intermediate orbit with a high AP can give good savings (the opposite of lowering PE to take advantage of Oberth)

[Alien Worlds Part Part Deux... Giant Mushrooms Instead Of Trees Sound Possible?]

Depends on what you mean by "fungi". This is alien biology so they presumably aren't related to our fungi. 

If by fungi you mean a sessile organism that obtains it's nutrition by breaking down dead organisms like most notable earth fungi then what is producing the matter to break down, and why do they need to grow metres into the air when dead stuff is on the ground?

If you want umbrella shaped photosynthetic organisms then sure, except given they aren't related to anything on earth I think the common name given to them is going to be plants because in common use a plant is a "multicellular organism that photosythesises"

 

[U.S. will lag behind in utilization of resources on the Moon.]

28k /kg can't be the whole cost of gold mining, there will be exploration costs and licensing costs on top of that to get towards the current price of 60k.

It's that price that the moon has to beat. If gold on the moon came in the form of conveniently stacked gold bars then I guess transport costs would only have to be 2,000 times cheaper than at present for it to make sense.

[How much dV and ISP do you need for a realistic interstellar ship?]

5 hours ago, farmerben said:

You get more thrust throwing alpha particles and electrons at 99% c than you do with photons only.

For a given energy source and exhaust velocity the relativistic mass of propellant used is simply given by kE=1/2mv^2 no matter what the propellant is. Thrust is proportional to momentum =mv. So if you are within multiple 9s of c the photons or other particles will have almost exactly the same thrust per Watt of power that goes into the propellant. And with photons directly you can throw away the accelerator, the electric generator, the cooling etc and all the inefficiencies that come with them.

Yes the thrust of a photon drive is awful, but it is always better than a relativistic accelerator.

[How much dV and ISP do you need for a realistic interstellar ship?]

If you want an exhaust velocity of you engine is approaching c then you might as well get rid of the particle accelerator and just emit the photons from your energy source. You'll get the same thrust and isp.

[For Questions That Don't Merit Their Own Thread]

The uranium won't suddenly come into a sphere at the centre, it will slowly diffuse inwards. The heat from fission reactions will expand the core slowing the reaction so the uranium will be burned up at a steady rate, just like the hydrogen fusion is stable.

Also the subs fusion output is 10^26 watts, the fusion of all that uranium is about the same number of joules so the fission of all the uranium in the sun is about a seconds worth of fusion.

[AI Will Never Be Sentient... Cyborgs On The Other Hand...]

When you can prove to me that you are conscious, or even define it then we can have a meaningful conversation about machine consciousness.

[Anybody working on support for joysticks and game controllers?]

Also there is an InputProcessor mod (that doesn't appear to have a forum thread) that seems to be working for my non-steam game

[SpaceX Discussion Thread]

9 hours ago, darthgently said:

Maybe they are losing parts and complexity related to stage 2 ullage? Not sure

But if they can maintain continuous thrust it would make a difference.  Try it in KSP, you'll see

But 10%? When the starship still needs RCS that could do the job and you need to add the extra mass of shielding the second stage.

And as for the idea that the craft is slowing down and needs to speed back up again, that energy is always going to be lost to gravity. There will be a loss to the oberth effect from burning the fuel higher but I can't believe that a few seconds difference makes more than a fraction of a percent.

[SpaceX Discussion Thread]

How would hot staging give a 10% payload improvement? I can't think of any way that the difference isn't trivial.

[Cheap Mass Produced Space Missiles Probably Won't Look Like An Earth Missile...]

The fuel tanks probably won't be spherical because spheres are much more of a pain to manufacture than cylinders.

[Science News Thread (for articles that don't relate to ongoing discussions)]

5 hours ago, JoeSchmuckatelli said:

That's playing fast and loose with the term, 'expert'.

Yup, he's completely ignoring the cost of recalibrating everyone's calendars.

[How Long Can You Keep Propellant Unused In A Tank Before It Expires?]

The alien ship isn't powered by something as primitive as hydrolox. That would have evaporated long ago and wouldn't have got it here/there in the first place. 

It's powered by unobtanium that our physics barely imagines/ can't comprehend at all.

Is unobtanium storable? Yes, it says so right there in the script.

[Do planets move toward or away from their Star?]

Good question. My guess is that both drag effects and solar wind are significantly smaller on something planet sized than the outwards spiralling caused by mass loss of the star. I hope someone who actually knows the answer comments though because I am curious.