For Questions That Don't Merit Their Own Thread

[magnemoe]

2 hours ago, V7 Aerospace said:

I'd imagine the main problem with using existing missiles to launch payloads on the moon is that being designed to work in atmosphere, the lack of air for control surfaces means that they'd be unable to stay on course. Unless the missile chosen already has some sort of thrust vectoring or such.

Obviously, easiest might be to put control surfaces in the bell if solid else tilt the engine. 
An monopropelant engine gives 230 isp, who is better than solid and more controllable, use newer less dangerous monoprop and an battery powered pump to feed engine (realistic hard scifi) 

Russia is assumed to have an UAV who is launched by rocket artillery. Primary role is to act as an spotter for the follow up bombardment but can also be used for other stuff like searching for snipers who would have an bad day if spotted.
 

[Racescort666]

39 minutes ago, magnemoe said:

Obviously, easiest might be to put control surfaces in the bell if solid else tilt the engine. 
An monopropelant engine gives 230 isp, who is better than solid and more controllable, use newer less dangerous monoprop and an battery powered pump to feed engine (realistic hard scifi) 
 

In KSP SRMs are kind of terrible. In real life, they have ISPs of 250-295*, come with thrust vectoring, and are probably less dangerous than any liquid you'd want to use as a monopropellant. They are used in munitions for good reason and John D Clark discusses it in Ignition.

*The range is from a quick glance through the old Orbital ATK catalog but these numbers are far better than the 200-235 listed in Aerojet's monopropellant catalog.

[magnemoe]

29 minutes ago, Racescort666 said:

In KSP SRMs are kind of terrible. In real life, they have ISPs of 250-295*, come with thrust vectoring, and are probably less dangerous than any liquid you'd want to use as a monopropellant. They are used in munitions for good reason and John D Clark discusses it in Ignition.

*The range is from a quick glance through the old Orbital ATK catalog but these numbers are far better than the 200-235 listed in Aerojet's monopropellant catalog.

Yes better you can terminate trust, would use reaction on satellite, you have time to orient satellite. 

[Gargamel]

13 hours ago, ARS said:

On the Lunar surface, with it's lower gravity than earth, is it practical for astronaut to deploy light microsatellite using shoulder mounted rocket launcher? Only instead of warhead it carries satellite payload and orbit circularization thrusters, so the rocket will be fired horizontally on Lunar surface on parabolic suborbital trajectory before using the onboard thrusters to circularize the orbit

One little problem with this idea....

 

[wumpus]

5 hours ago, Racescort666 said:

In KSP SRMs are kind of terrible. In real life, they have ISPs of 250-295*, come with thrust vectoring, and are probably less dangerous than any liquid you'd want to use as a monopropellant. They are used in munitions for good reason and John D Clark discusses it in Ignition.

*The range is from a quick glance through the old Orbital ATK catalog but these numbers are far better than the 200-235 listed in Aerojet's monopropellant catalog.

On the other hand, KSP SRMs are *cheap*, and have all the thrust of their real-life counterparts.  Any "cost/kg to orbit" contest has typically seen plenty of kicker motors for the first stage.  In real life, don't expect any such deals.

Low Isp isn't all that important if you have a heavy second stage being lifted by a first stage.  As the payload (including any later stages) becomes a greater and greater portion of the total mass ratio, the efficiency of the rocket goes more and more linear (Isp/Isp, as opposed to going full logarithmic as the ratio becomes small).  And don't forget just how brutal gravity losses can be in the early portion of the flight: the cheap thrust of SRBs can easily make up for the lower Isp, especially if your TWR starts to approach 2 (or more).

In reality, this shows up more in those little SRB boosters that surround many modern rockets.  I think they help overcome gravity losses for about a minute and then drop off.

[cubinator]

Does lava boil in a vacuum? What about purer molten metals like aluminum or iron or gold?

Edited March 29, 2019 by cubinator

[ZooNamedGames]

In the 119 pages this thread has, its probably been asked before, but what's with orbiter Columbia's unique wing strakes, being black instead of white as we see with the rest of the orbiter fleet?

On 3/27/2019 at 8:26 PM, Gargamel said:

One little problem with this idea....

 

Thankfully the moon's gravity is unstable enough for there to be a high likelyhood that arrow wouldn't make it the whole way back around.

[StrandedonEarth]

16 minutes ago, ZooNamedGames said:

In the 119 pages this thread has, its probably been asked before, but what's with orbiter Columbia's unique wing strakes, being black instead of white as we see with the rest of the orbiter fleet?

Columbia was the first orbiter, so they only had 70’s era simulations and guesstimates of where the hot spots would be, so they put tiles and RCC wherever they thought might need it. With data from Columbia, they were able to determine where less TP was needed, and modified accordingly. The wing strakes didn’t need as much black RCC, and the OMS pods could swap out some tiles for thermal blankets. 

Edited March 29, 2019 by StrandedonEarth

[DAL59]

Why can I watch 4k video with no lag, but a 4k image takes a full minute to load?  

[ZooNamedGames]

1 minute ago, DAL59 said:

Why can I watch 4k video with no lag, but a 4k image takes a full minute to load?  

sounds like a case of your computer having to read data from the HDD. It's faster to stream data from the internet than for your HDD to spin and pull data. It's why I've upgraded from my HDD to a SDD, the load times at lightning fast in comparison.

[magnemoe]

9 minutes ago, ZooNamedGames said:

sounds like a case of your computer having to read data from the HDD. It's faster to stream data from the internet than for your HDD to spin and pull data. It's why I've upgraded from my HDD to a SDD, the load times at lightning fast in comparison.

Hard drives are faster than most internet connections. 
Sounds more like the program you use to open the image with is slow. If online the image might be on an slower server with more load than youtube datacenter.

[p1t1o]

1 hour ago, cubinator said:

Does lava boil in a vacuum? What about purer molten metals like aluminum or iron or gold?

All boiling points are depressed in a vacuum, relative to 1atm. Whether or not a certain liquid "boils" is another question. Sub-boiling evaporation would also be greatly accelerated. Even solid materials slowly sublimate in vacuum, although this process is very slow and varies greatly depending on the properties of the material. Some metals (eg: zinc) are precluded from use in space because they sublimate too quickly.

 

20 minutes ago, DAL59 said:

Why can I watch 4k video with no lag, but a 4k image takes a full minute to load?  

Video is (most often) compressed, if it was streaming 30 full-res, uncompressed 4k images to you per second, yes there would be a ton of lag. 

A 4k jpeg, for example, ought to load up pretty quick.

4k is just the number of pixels, it doesnt imply anything about size of the data. 

Edited March 29, 2019 by p1t1o

[ZooNamedGames]

16 minutes ago, magnemoe said:

Hard drives are faster than most internet connections. 
Sounds more like the program you use to open the image with is slow. If online the image might be on an slower server with more load than youtube datacenter.

Depends on the ISP I guess. I get an average of 2Mb/s of load speed on the internet. Which I can easily achieve and exceed with my SDD.

Edited March 29, 2019 by ZooNamedGames

[magnemoe]

59 minutes ago, ZooNamedGames said:

Depends on the ISP I guess. I get an average of 2Mb/s of load speed on the internet. Which I can easily achieve and exceed with my SDD.

You will get way more, copying an large file on an standard cheep harddrive is easy +60 MB/s, that is  500 Mb/s as harddrives measure in MB not Mb. An SSD is typicaly +10 times faster.
 Note that internet is fast opening many small files like an page with loads of thumbnails, here internet might beat an standard harddrive but not an SSD. 
 

[tater]

https://www.bbc.com/news/science-environment-47755275

Pretty interesting.

Better article:

https://news.berkeley.edu/2019/03/29/66-million-year-old-deathbed-linked-to-dinosaur-killing-meteor/

 

[tater]

This is cool:

https://t.co/ocTAmAjAuT

("Map" of Apollo flight with a lot of annotation for burns, specific events, etc)

[ChrisSpace]

Is Europa's ocean best described as being "fresh" water or salt water?

[kerbiloid]

Brine.

Because its conductivity creates a kinda magnetosphere.

[ARS]

If space elevator's tether that connects the space installation with earth breaks/snapped, should the installation above it fall back to earth or thrown into deep space?

[Green Baron]

Immediately, the upper part would drift away, the lower wrap around the earth. Depending on the counterweight and mass distribution the upper part might assume an elliptical orbit, return to mama later, or escape, i'd say.

[kerbiloid]

It will be a huge whip in the skies, up to ~30 000 km long, dangling around the Earth..

[Superfluous J]

1 hour ago, ARS said:

If space elevator's tether that connects the space installation with earth breaks/snapped, should the installation above it fall back to earth or thrown into deep space?

It would stay in orbit. The tether is not holding the station to Earth, and it's assuredly not holding it UP.

The station's orbit would change, for sure, as the cable is probably in total a significant portion of the station's mass, and depending on where the cable snapped, the station's center of mass could shift ... well I really don't know, dozens of km? Hundreds?

I remember reading about a second tether splayed out "behind" or "above" the station, 180 degrees from Earth, that would serve both as a launch tether (you could go out it, then let go and be flung away) and also be able to be cut, to keep the station orbiting at roughly the same place if the Earth tether were to be cut for some reason.

[adsii1970]

31 minutes ago, 5thHorseman said:

The station's orbit would change, for sure, as the cable is probably in total a significant portion of the station's mass, and depending on where the cable snapped, the station's center of mass could shift ... well I really don't know, dozens of km? Hundreds?

But remember, the tether has potential energy, much like the line or cable which holds an astronaut to a capsule or the ISS. Depending on mass and velocity, the severing of a space elevator cable has the potential to be bad for those in the orbiting platform.

The impact of that much cable on Earth would result in damage only to the area hit - which the subject could be fun for one of those cheesy and bad SYFY Channel disaster movies. 

But as far as the orbital platform, I doubt it would toss it out of Earth's orbit. So, no Space 1999 scenario. But I do believe you are correct in the rest of your statement; it would most definitely alter the orbit. Possibly a more elliptical orbit because I do not think it would have enough inertia to reach escape velocity. But this is pure speculation. 

[StrandedonEarth]

In Kim Stanley Robinson’s Red/Green/Blue Mars trilogy...

Spoiler

The fall of a Martian space elevator cable is described  

 

[Spaceception]

I have a feeling that I once read about why fusion was always 20 years away. And it was here. It was something about researchers expecting a similar rate of the development of fusion, to be similar to the development rate of fission, or something along those lines. That didn't work out. Because turns out, fusion was actually really hard to sustain, but that 20-year thing stuck. Can anyone confirm that? And are there any sources for more reading? Thanks

Edited April 1, 2019 by Spaceception