For Questions That Don't Merit Their Own Thread

[p1t1o]

 

50 minutes ago, kerbiloid said:

I defintely wouldn't spend twice more energy than required.

Why not? Are you paying by the m/s?

I think it'd be fun to shoot a full-bore ICBM horizontally, burst it as it goes hypersonic over the target. Very possible on Mars/Moon.

"Dodge This" I'd say

 

I've also wondered, many ICBMs have orbital capability if you reduce the payload enough, so it got me thinking:

Saturn V is orbit capable....what size warhead do we need to put on it in order to bring it down to merely ICBM-capable?

[kerbiloid]

13 minutes ago, p1t1o said:

Are you paying by the m/s?

Of course. I'm paying to deliver it from Earth.
I can get two for the price of one.

18 minutes ago, p1t1o said:

Saturn V is orbit capable....what size warhead do we need to put on it in order to bring it down to merely ICBM-capable?

https://en.wikipedia.org/wiki/B41_nuclear_bomb

Quote

It was the highest-yield nuclear weapon ever deployed by the United States, with a maximum yield of 25 megatons (Mt), and weighing in at 4,850 kg (10,690 lb). It remains the highest yield-to-weight ratio of any weapon created. The US claimed in 1963 that it could produce a 35 Mt fusion bomb, and put it on a Titan II(3,700 kg [8,200 lb] payload), almost doubling the yield-to-weight ratio of the B-41.

25 Mt / 4.85 t = 5.2 Mt/t
35 Mt/3.7 t = 9.5 Mt/t (probably somebody tells a fairy tale)

A602EN

Spoiler

100 Mt/27t =3.7 Mt/t

So, up to 5 Mt/t without miracles, 10 Mt/.t - with them.

So, Saturn V = 600..1200 Mt.

Afaik, N-1 warhead was also estimated ~1000 Mt.

[StrandedonEarth]

45 minutes ago, p1t1o said:

I've also wondered, many ICBMs have orbital capability if you reduce the payload enough, so it got me thinking:

Saturn V is orbit capable....what size warhead do we need to put on it in order to bring it down to merely ICBM-capable?

Replace everything above S2 with a slightly lighter warhead. Saturn V only needed the first two stages to lift Skylab, and only a shortish burn of S3 to circularize for the lunar stack...

[Fraktal]

Questions involving not real stuff.

Suppose the technology is available to construct a high-thrust (variable exhaust velocity, can be dialed all the way up to low c-fractional) ion engine fueled by a ramscoop. Ramscoop takes care of the fuel (atmosphere or stellar plasma in the interplanetary/interstellar medium, basically any gas that can be ionized), Isp increases with density of the ambient medium (greater fuel availability in atmosphere -> same thrust possible at a lower exhaust velocity, less efficient in interplanetary/interstellar space; thrust-to-pressure curve is like that of a jet engine that only flames out in absolute vacuum), but electricity requirements are extraordinarily high (like, "dedicated nuclear reactor per engine" high if operating in space with a desired thrust comparable to a conventional rocket engine) and the exhaust is... kinda dangerous.

Now, some number crunching says a bit more than two days' worth of acceleration at 1 TWR would cover the Earth-Sun distance if we're not intent on stopping and two and a half weeks would be able to reach anywhere within the Sol system regardless of transfer windows. Which sounds awesome.

Question #1. What kind of power and efficiency are we looking at for the particle accelerator required to achieve low c-fractional exhaust velocity without being several kilometers long?

Question #2. How dangerous would the engine exhaust be? I'm figuring "blind everyone looking at it from the side within a few kilometers away, slice entire spacecraft in half from dozens of kilometers away, kill entire crew with hard radiation from a thousand kilometers away" dangerous.

And of course the requisite Question #3... how kerbal would this thing be?

[Mad Rocket Scientist]

13 hours ago, kerbiloid said:

Of course. I'm paying to deliver it from Earth.
I can get two for the price of one.

https://en.wikipedia.org/wiki/B41_nuclear_bomb

25 Mt / 4.85 t = 5.2 Mt/t
35 Mt/3.7 t = 9.5 Mt/t (probably somebody tells a fairy tale)

A602EN

  Reveal hidden contents

100 Mt/27t =3.7 Mt/t

So, up to 5 Mt/t without miracles, 10 Mt/.t - with them.

So, Saturn V = 600..1200 Mt.

Afaik, N-1 warhead was also estimated ~1000 Mt.

For some context, Tsar bomba, the largest nuclear weapon ever made was 100 mt. The entire current worldwide nuclear arsenal combined is 1460 mt. 

[ARS]

2 hours ago, Mad Rocket Scientist said:

Tsar bomba, the largest nuclear weapon ever made was 100 mt

It's actually 50 megaton. The original design does have 100 megaton yield, but the bomb was scaled down to 50 megaton when they realized the bomber won't be able to clear the blast zone in time after dropping a nuclear bomb with 100 megaton yield

[Xd the great]

1 hour ago, ARS said:

It's actually 50 megaton. The original design does have 100 megaton yield, but the bomb was scaled down to 50 megaton when they realized the bomber won't be able to clear the blast zone in time after dropping a nuclear bomb with 100 megaton yield

Gonna do that with bda.

Anyway, why did the lunar asent stage on apollo use corrosive stuff? They cant test it beforehand and any spacex people will tell you it is a bad idea.

[kerbiloid]

3 hours ago, ARS said:

50 megaton

58

3 hours ago, ARS said:

The original design does have 100 megaton yield, but the bomb was scaled down to 50 megaton

It wasn't scaled. They just replaced the external uranium layer with lead, because it' (layer) was just just a passive device and didn't effect the bomb working itself, so there was no reason to increase the radius of destructions and chances of bomber damage.

2 hours ago, Xd the great said:

Gonna do that with bda.

It was done, but stays 1.3.1.

 

[Xd the great]

nah, im gonna mes with the cfg files.

[IncongruousGoat]

Here's one for all the armchair astrophysicists in the room:

What's the most efficient way to use the Sun? I've heard the idea bandied about that the Sun isn't terribly efficient as a fusion reactor, but it would also take a lot of energy to take apart the Sun. So, what's the most efficient way to use the hydrogen content of the Sun as a power source? Dyson swarm? Take it apart and make red dwarf stars out of it, then surround those with Dyson swarms? Fusion reactors aren't really practical; the hydrogen in the Sun is almost entirely protium, not the deuterium or tritium one would want for a fusion reactor.

[kerbiloid]

Depends on your project duration. Do you want to have all at once or to have a heater as long as possible.

Edited July 24, 2018 by kerbiloid

[K^2]

2 hours ago, IncongruousGoat said:

I've heard the idea bandied about that the Sun isn't terribly efficient as a fusion reactor

The Sun is 100% efficient as a fusion reactor. It's another matter that it will not burn entirely through, due to its small size. If you want to convert more of its mass into energy, you need to make larger stars, not smaller ones.

Of course, if you don't think fusion itself is sufficiently efficient, then what you really want is a black hole. If used right, it can convert nearly 100% of mass into energy. Again, the key here is to go bigger, not smaller.

[magnemoe]

On 7/21/2018 at 11:44 AM, Xd the great said:

Gonna do that with bda.

Anyway, why did the lunar asent stage on apollo use corrosive stuff? They cant test it beforehand and any spacex people will tell you it is a bad idea.

They wanted storable fuel and oxidizer, it had to survive the trip to the moon and the stay on surface. They wanted hypergolic so it did not need any starter function who could fail. 
All uses storable hypergolic for long duration space missions as in anything other than launches. 

SpaceX BFR and ULA centaur replacement plans to use oxygen and methane or hydrogen but none of them has flown. 

[kerbiloid]

On 7/21/2018 at 12:44 PM, Xd the great said:

why did the lunar asent stage on apollo use corrosive stuff

Which stuff is corrosive? They used aerozine-50 and NTO.

[Xd the great]

12 minutes ago, kerbiloid said:

Which stuff is corrosive? They used aerozine-50 and NTO.

Nto is oxidizing, so its KINDA corrosive.

And i heard that they could not test the lunar asent stage engine as it gets destroyed too quickly during firing.

[kerbiloid]

1 minute ago, Xd the great said:

Nto is oxidizing,

SLBM and ICBM fueled with NTO stay for 10+ years fueled.

Some SLBM keep their engine sunk in the NTO, for 10+ years.

While lunar flight lasts for a week.

NTO is usually inhibited.

[Xd the great]

Oh my mistake, must be the exhaust.

[p1t1o]

There is a "source" on the wiki page that corroborates your claim, but the link is dead so no further info on it

 

Edited July 24, 2018 by p1t1o

[magnemoe]

4 hours ago, Xd the great said:

Nto is oxidizing, so its KINDA corrosive.

And i heard that they could not test the lunar asent stage engine as it gets destroyed too quickly during firing.

Rater system was so simple it was little benefit testing it, it was also an vacuum engine who can not be tested on earth. Other versions was tested. System was simply two helium pressure vessels who pressurized the fuel and oxidizer, then two valves who let fuel and oxidizer into the engine. Yes it was more to it as in electronic to time burns and so but the engine was idiotic simple. 

[Xd the great]

29 minutes ago, magnemoe said:

Rater system was so simple it was little benefit testing it, it was also an vacuum engine who can not be tested on earth. Other versions was tested. System was simply two helium pressure vessels who pressurized the fuel and oxidizer, then two valves who let fuel and oxidizer into the engine. Yes it was more to it as in electronic to time burns and so but the engine was idiotic simple. 

Ah I see. Minimalist is always fun. 

[StrandedonEarth]

8 hours ago, Xd the great said:

Ah I see. Minimalist is always fun. 

More to the point, reliable. Very few potential failure points 

[magnemoe]

16 minutes ago, StrandedonEarth said:

More to the point, reliable. Very few potential failure points 

And this is important for stuff who will not fail safe. Getting stuck on the Moon is not safe. 
You can add layers on top. An car can have auto braking system on top of ABS, if both fails the brakes will still work. You can also loose the servo and one of the piping. 
 

[kerbiloid]

Because ascent stage had no external constraints.

The more constraints you have - the more complicated system you have to have to keep it reliable. Simple systems would fail where complicated ones work.
Say, a train.

[Diche Bach]

On 7/24/2018 at 3:48 AM, K^2 said:

The Sun is 100% efficient as a fusion reactor. It's another matter that it will not burn entirely through, due to its small size. If you want to convert more of its mass into energy, you need to make larger stars, not smaller ones.

Of course, if you don't think fusion itself is sufficiently efficient, then what you really want is a black hole. If used right, it can convert nearly 100% of mass into energy. Again, the key here is to go bigger, not smaller.

Uhh . . . given that nothing escapes a black hole, how could one consider it to be an "energy source?"

ADDIT: and going back to the question to which you responded "What is the most efficient way to use the sun?"

What about photosynthesis? Is anything actually "more efficient" than that?

Edited July 25, 2018 by Diche Bach

[Steel]

1 hour ago, Diche Bach said:

Uhh . . . given that nothing escapes a black hole, how could one consider it to be an "energy source?"

ADDIT: and going back to the question to which you responded "What is the most efficient way to use the sun?"

What about photosynthesis? Is anything actually "more efficient" than that?

Photosynthesis is horribly inefficient, I think man-made solar panels are better by a factor of 10 or so.