For Questions That Don't Merit Their Own Thread

[Kryten]

How much dpi would you need to be able to zoom in on a picture of yourself taken at arms length, and see the quarks making up the parts of your atoms?

Quarks have no volume, there's nothing to see.

[Kinglet]

Quarks have no volume, there's nothing to see.

Well, let me rephrase it a bit: To be able to see the particles making up the atoms. And also ignoring the fact that light is photons. Let's just assume it's possible to see anything that has surface if you look hard enough.

[K^2]

Well, let me rephrase it a bit: To be able to see the particles making up the atoms. And also ignoring the fact that light is photons. Let's just assume it's possible to see anything that has surface if you look hard enough.

All elementary particles are point particles. Your question is meaningless.

[PB666]

https://gigaom.com/2015/08/24/heres-why-american-students-dont-learn-computer-science/

I will just state that I never learned computer science in High School

I had one semester in Fortran, learned Cobol (extinct now I guess) and a Statistics program

Taught myself Basic, QuickBasis, VIsual Basic, VBA

At one point I could at one point I could write code for Z80 in hexadecimal notation. (one step lower than assembly language). By the time I finished I had a program that forced an appleIIe with a black and white monitor to rewrite itself 2 times to print out color images on an apple writer, lol.)

Learned and did a little bit in C (Would do more but cannot find a pressing application that supercedes needs of VB - mostly do monte carlo analysis now)

Also taught myself Visicalc, MS Excel. No training what-so-ever to write VBA for Excel, never had any training for word or powerpoint.

Fortran we used to input on MUSIC, it would punch things out on cards and we would give the cards to the program processors and they would split out sheets of code and output.

I have taught other people who have no computer skills in VB to teach themselves how to program.

The problem in the US is that the value of STEM for life careers simply is not emphasized, we worry more about religion and social culture than technology and the end result is that we have 2% more unemployement than we would otherwise have.

Edited August 25, 2015 by PB666

[shynung]

What are the advantages and disadvantages of having a spacecraft with the engines in front of the payload, as opposed to behind, like the ISV Venture Star from the movie 'Avatar'?

[Superfluous J]

What are the advantages and disadvantages of having a spacecraft with the engines in front of the payload, as opposed to behind, like the ISV Venture Star from the movie 'Avatar'?

http://simplywallpaper.net/pictures/2010/04/28/Space-Ship-Over-Pandora.jpg

The advantage is that by pulling your payload instead of pushing it, you eliminate Wiggly Rocket Syndrome. The detriment is that your engines can get confused and gimbal the wrong way, causing no end of hilarity trouble.

[theend3r]

Like 5thHorseman said. If you can set it up right, it's simply better. It's also nearly mandatory for asteroid tugs or at least by far the easiest way.

[sgt_flyer]

What are the advantages and disadvantages of having a spacecraft with the engines in front of the payload, as opposed to behind, like the ISV Venture Star from the movie 'Avatar'?

http://simplywallpaper.net/pictures/2010/04/28/Space-Ship-Over-Pandora.jpg

The venture star design is built to workaround several problems - the thing uses antimatter for it's engines, and antimatter / matter annihilation generate a lot of radiations. So, they want the living quarters to be as far as possible from the source of these radiations - which means having a long ship - and câbles of a given size can support enormous tensile strengths for low weights, but are flexible. So a puller configuration with a cable structure can be lenghtened much more easily than building a solid truss structure to space the living quarters from the engines in a pusher configuration. (In the end, the things ends up being lighter)

In real life, we can support extremely high loads with comparatively thin cables

[RainDreamer]

I imagine that thing would have to deal with structural stress when it try to turn though, when the front goes one way and the back, due to inertia, keep on going on the same path before being dragged along. Kind of like when you bank too hard with a too powerful engine while towing a massive asteroid in KSP. Then again, I might misunderstood something.

[shynung]

The advantage is that by pulling your payload instead of pushing it, you eliminate Wiggly Rocket Syndrome. The detriment is that your engines can get confused and gimbal the wrong way, causing no end of hilarity trouble.

Hmm. I'm thinking of a scenario where one engine suddenly loses thrust while the other still firing. Given that the rest of the rocket is at the end of a long cable, we might see Swinging Rocket Syndrome. That, and the payload going into the exhaust plume.

Also, there might be problems with ship attitude control. RCS action mismatches could relieve tension on the cable, which could bend the ship enough to push the payload into the exhaust plume. This, in addition to the difficulties of maneuvering what is essentially two bricks tied together with a cable. This thing probably wasn't meant to dock to a space station of some sort, but have shuttles bringing stuff to and from a nearby station instead.

[K^2]

Hmm. I'm thinking of a scenario where one engine suddenly loses thrust while the other still firing. Given that the rest of the rocket is at the end of a long cable, we might see Swinging Rocket Syndrome. That, and the payload going into the exhaust plume.

Exhaust travels at several km/s. If your rocket is twisting fast enough to hit its own exhaust, it's already ripping itself into pieces due to extreme centrifugal stress.

Otherwise, this is a problem with any multi-engine configuration, regardless of where the engines are placed. Of course, if your engines are in the front, you are forced into multi-engine. So there's that.

[RainDreamer]

My question with that cable method is... How do you slow down without getting the back part smashing to the front?

[AngelLestat]

My question with that cable method is... How do you slow down without getting the back part smashing to the front?

Easy, you turn around first, and then you slow down.

The Venture Star is not a cable, but its similar. If we see the middle truss between the two radiators, that is the Sail support, in the other end of the ship we have the shield, which is used to shield the ship from the laser beam, and once the acceleration is over, it turns all the ship, so it can be used as particle shielding.

To slow down in the arrival it use the antimatter engines. The process is repeat it from pandora to earth, with the difference than the acceleration is done by antimatter, and the desaceleration by beamed sail.

Edited August 27, 2015 by AngelLestat

[RainDreamer]

Right, for some reason I was thinking it would flip the engine...that doesn't make sense. Just turning around to do a retrograde burn would be like any other engine set up.

[PB666]

http://www.eurekalert.org/pub_releases/2015-08/sjcu-sl082715.php

So the question what proprerty of the light did the make more variable if noise was reduced?

[shynung]

Inside a star system, how fast does a spacecraft needs to go before a Bussard ramjet drive becomes usable?

[PB666]

Inside a star system, how fast does a spacecraft needs to go before a Bussard ramjet drive becomes usable?

Are you traveling away from, toward or tangential to the star. The question should be if a ship is traveling the same speed as the stellar wind, how fast would it need to go would be dependent on the density of plasma within the wind. On the bright side you don't have to generate plasma, on the not so bright side you may have to slingshot close to the star to get enough forward momentum to escape, and you would have to accelerate at break neck speeds.

The drive is not so speculative as a warp drive, but much more speculative than anything planned and the problem is that you either need a very efficient nuclear reaction on a scale that has not been created in any laboratory or you have to find away to do tetraproton fusion, which is, as far as I know impossible in a single step.

[jiminator]

Inside a star system, how fast does a spacecraft needs to go before a Bussard ramjet drive becomes usable?

The article you posted gives it as

A Bussard ramjet has to be boosted to a certain minimum speed before the scoop can operate. Estimates range from 1% to 6% of c, which is pretty awful.

so about 3000000 to 18000000 m/sec

[shynung]

Are you traveling away from, toward or tangential to the star.

2 scenarios: towards the star (entering a star system), and away from the star (exiting a star system).

Let's assume a 10 million km² scoop field, for the sake of the question.

The article you posted gives it as

so about 3000000 to 18000000 m/sec (my addition: 3 000 to 18 000 km/sec)

The article does not clarify whether this is in interstellar space or inside star systems, where the particle density is higher.

Edited September 2, 2015 by shynung

[AngelLestat]

Inside a star system, how fast does a spacecraft needs to go before a Bussard ramjet drive becomes usable?

A bussard ramjet is only usefull as brake, because the drag you get is higher than the acceleration.

But the system will add so much mass, that it would be more usefull to have a magsail for the job.

[shynung]

A bussard ramjet is only usefull as brake, because the drag you get is higher than the acceleration.

But the system will add so much mass, that it would be more usefull to have a magsail for the job.

Depends on what one does with the collected gas. If I were to heat it by funneling it through a reactor core, for example, I can get net thrust simply by piping it into a rocket nozzle.

What I'm asking is how fast the ship must go inside a star system, where the particle density is higher than interstellar space, so that the ram pressure on the collected hydrogen gas is enough to make it do fusion on its own. If this is successful, not only my propellant is unlimited, so is my nuclear fuel source. My deltaV would be essentially infinite.

[Hcube]

New question : The observable result of a B+ radioactive desintegration is a diffused spectrum right ? Not with stripes but some kind of curve instead ? (If this first assumption is wrong tell me already). If so, how is it possible since the positon/electron annihilation emits two 0,511MeV gamma-photons ? Those should result in a spectrum with stripes... There is no probabilist repartition of the energy(at this point)...

It's not like the neutrino is being detected haha What is it?

Can anyone enlighten me ? Thanks

[AngelLestat]

One time I ask to a scientist if the bussard ranjet would be at least usufull in case you carry only anti-hydrogen, so you need only collect the hydrogen from space (reducing your proppellant mass by half), and not even in that case was usefull to accelerate.

So I imagine than it will be even less usefull in the fusion case. No matter how you collect the matter, you are produccing a huge deltav change in each of those particles that you need to restore, the same particle mass as energy is not enoght I guess.

About the speed needed to brake.. faster you go, more efficient it is.

[SargeRho]

A bussard ramjet is only usefull as brake, because the drag you get is higher than the acceleration.

But the system will add so much mass, that it would be more usefull to have a magsail for the job.

Not true. A Bussard Ramjet could get up to 20% of the speed of light. A RAIR can probably get much faster.

I think it has to be going at 1% of the speed of light before it collects enough hydrogen to function, and the drag doesn't cancel out the thrust until it's at 20%.

-----

Now I have a question, how viable would the idea of storing heat in something like a diamond heatsink, and jettisoning that, to get rid of extreme heat peaks in a spacecraft, such as from firing a laser or some other high-energy system?

[AngelLestat]

You have a source claming that?

I guess there is this idea that if you have a funnel you are not changing the deltaV of the particles... that is a lie.

At low speed might have more chances to succeed, but I guess your funnel should be so big, that the mass added would total neglect the deltaV added for that proppelent.