For Questions That Don't Merit Their Own Thread

[Skyler4856]

When one mixes aluminum with hydrochloric gas, the chlorine combines with the aluminum, leaving an excess of hydrogen, this begs the question: If one were to consume enough aluminum, could it mix with the gastric acid in your stomach in such a way as to blow the stomach up?

[Kryten]

When one mixes aluminum with hydrochloric gas, the chlorine combines with the aluminum, leaving an excess of hydrogen, this begs the question: If one were to consume enough aluminum, could it mix with the gastric acid in your stomach in such a way as to blow the stomach up?

It's doubtful-you'd need to produce quite a lot of gas to overwhelm the existing mechanisms for getting rid of it (i.e. burping), and the stomach isn't really all that acidic in the grand scheme of things.

[Skyler4856]

How much sunlight would one have to reflect off the earth to ccool it by one degree

[Sirrobert]

How much sunlight would one have to reflect off the earth to ccool it by one degree

Climate is way to complex to be able to sumerize the entire thing in such a small question.

We don't even know what the weather will be next week

[K^2]

How much sunlight would one have to reflect off the earth to ccool it by one degree

Assuming all else stays the same, radiated energy is proportional to T⁴. If E₀ = kT⁴ and E₁ = k(T - 1K)⁴, then E₁ = E₀ * (1 - 4K/T) to first order. At mean T = 288K, 4K/T = 1.4%. So you'd need to reflect 1.4% of incoming energy to bring equilibrium temperature down by 1K or 1°C.

[Skyler4856]

Assuming all else stays the same, radiated energy is proportional to T⁴. If E₀ = kT⁴ and E₁ = k(T - 1K)⁴, then E₁ = E₀ * (1 - 4K/T) to first order. At mean T = 288K, 4K/T = 1.4%. So you'd need to reflect 1.4% of incoming energy to bring equilibrium temperature down by 1K or 1°C.

Thanks mate

[Robotengineer]

Will the Bigelow Aerospace BEAM be added to the ISS this year?

[gooddog15]

Yes, on the Dragon CRS-8 mission scheduled to fly on September 2nd.

[KSK]

Yeah, that. Though, I'm not thinking of natural fusion like inside stars, that is, up until iron. I'm thinking about heavier elements further down the periodic table. That is, fusing lighter atoms to get some energy, and using this energy to fuse iron (or heavier) atoms to make things like lead, gold, tungsten, or platinum, in a controlled fashion. Is that process possible?

Perfectly possible but not economically. We can even make synthetic elements that don't occur naturally, essentially by smacking the right isotopes together at speed.

[Robotengineer]

When will the ISS reenter the Earths atmosphere?

[Nibb31]

The ISS can't reenter the atmosphere because it is reboosted on a regular basis to counter the effects of drag. It experiences drag because, although it orbits at around 400km, there is still a very tenuous atmosphere at that altitude.

At the end of its life, the ISS will not reenter on its own though. That would be too dangerous, because due its size, not all of it will burn up, so some parts are bound to reach the surface. It will be deorbited in a controlled fashion, so that any debris ends up in the ocean. The plan is to send up a Progress or some other unmanned vehicle to perform the deorbit burn.

[Robotengineer]

The ISS can't reenter the atmosphere because it is reboosted on a regular basis to counter the effects of drag. It experiences drag because, although it orbits at around 400km, there is still a very tenuous atmosphere at that altitude.

At the end of its life, the ISS will not reenter on its own though. That would be too dangerous, because due its size, not all of it will burn up, so some parts are bound to reach the surface. It will be deorbited in a controlled fashion, so that any debris ends up in the ocean. The plan is to send up a Progress or some other unmanned vehicle to perform the deorbit burn.

Has that been scheduled yet? Or are they going to keep using it for as long as they can and then bring it down?

[Karriz]

Has that been scheduled yet? Or are they going to keep using it for as long as they can and then bring it down?

At the moment, the American portion of the station is funded until 2024, and Russian portion till 2020. It's likely that there will be further extensions to the lifespan, maybe till 2028. Current political situation is just slowing things down a bit. Also, Russians have some plans to detach their modules at some point and use those as a basis for new station, called OPSEK, but we'll see if they actually do that.

I just hope that ISS will have been replaced by a new station by the time it gets deorbited. Since NASA wants to move low-Earth orbit spaceflight to private businesses, they may be happy to use the future Bigelow station as a replacement.

[PB666]

In order to make an invisibility cloak/shield that works in air/vacuum, which have optical density near 1, you need a material with optical density less than 1. In other words, a material in which speed of light is greater than speed of light in vacuum. Fortunately, you only care about phase velocity for optical properties, not the group velocities. And so metamaterials with such property do exist. Unfortunately, nobody managed to make them into something that can actually be made into a solid object. So invisibility cloaks remain firmly in the realm of science fiction. There are plenty of people working on this, however, and some aerogel approaches are promising.

If you happen to have a medium with high index of refraction, like water, the problem is much easier. There are plenty of plastics with lower index of refraction, and transparent spheres that make their contents invisible when submerged under water do exist. Don't know why they aren't commercially available, to be honest. Would be a cool thing for hiding stuff in aquariums.

The solution for large scale invisibility does not work on large scale (>cm) like that demonstrated on small scale. What you need are high powered directional LEDs that directional illuminate along the EM vectors on the other side of the ship good at great distance with low resolution imaging. They would have to compensate for punctate distribution and you would need some sort of distortional mechanism. Of course you would need stereoscopic cameras that could evaluate all the light directions.

I Never actually see the need for cloaking in space, in space the default state of most smaller than an asteroid objects is not to be detected, even when looked at. A better choice in space is a decoy that sends out pulse to those who it wants to observe. Broad spectrum black paint will cover most scenarios. The IR signal is probably the most revealing but this can be dealt with by heat channeling and lasers.

[bobskythecanadianguy]

Will DSCOVR use a PAM or something similar to circularize at L1? When will it arrive there? And did the Falcon 9 put it in a 200km by 200km orbit, an L1 transfer orbit, or a full L1 orbit?

[Kryten]

Will DSCOVR use a PAM or something similar to circularize at L1? When will it arrive there? And did the Falcon 9 put it in a 200km by 200km orbit, an L1 transfer orbit, or a full L1 orbit?

L1 transfer, and DSCOVR will use a monopropellant hydrazine thruster to enter and maintain orbit. It was originally intended to be sent out on a small solid stage with poor injection accuracy, so has a lot of delta-v to compensate for that, about 600m/s.

[Kibble]

Kryten how do you know so much stuff about stuff?

[PB666]

The ISS can't reenter the atmosphere because it is reboosted on a regular basis to counter the effects of drag. It experiences drag because, although it orbits at around 400km, there is still a very tenuous atmosphere at that altitude.

At the end of its life, the ISS will not reenter on its own though. That would be too dangerous, because due its size, not all of it will burn up, so some parts are bound to reach the surface. It will be deorbited in a controlled fashion, so that any debris ends up in the ocean. The plan is to send up a Progress or some other unmanned vehicle to perform the deorbit burn.

If they place the massless EM drive on it it literatally could stay aloft as long as their were computers that can control orientation and thrusting dynamics. In addition it is now not so many delta v from being in a permanent orbit so if they simply boosted it to a higher orbit it could stay up forever.

- - - Updated - - -

When one mixes aluminum with hydrochloric gas, the chlorine combines with the aluminum, leaving an excess of hydrogen, this begs the question: If one were to consume enough aluminum, could it mix with the gastric acid in your stomach in such a way as to blow the stomach up?

I would light too many matches in the bathroom.

- - - Updated - - -

First of all, it would probably outgas, losing most of its water. It would probably freeze too, so it would end up tasting like dehydrated frozen cheese, whatever that tastes like.

It would freeze while it was outgassing, once that had occurred the proteins would be lyophilized and crysaline powder, but the oils would differentially freeze and interact with the proteins, therefore it would be heterogenous. Some of the lighter oils would outgas, eventually, and unsaturated fats would be the first to undergo radiative degradation and eventually degassing, leaving a black brown residue behind.

[Nibb31]

If they place the massless EM drive on it it literatally could stay aloft as long as their were computers that can control orientation and thrusting dynamics. In addition it is now not so many delta v from being in a permanent orbit so if they simply boosted it to a higher orbit it could stay up forever.

There is no such thing as a massless EM drive. NASA was planning to experiment a VASMIR drive though, but the project has been delayed by lack of funding

The ISS is not designed for the radiation environment of higher orbits. It's for LEO only, below the Van Allen belts.

Also, moving it higher makes it harder to reach, which means a reduction in cargo and crew payload capability.

Edited February 15, 2015 by Nibb31

[K^2]

I think, his idea is to boost it to higher orbit, so that it can keep serving as an unmanned, autonomous station. Maybe as an emergency supply store. Not a proper manned station. Could be a nice museum piece some day. I see no reason not to do this, since it would cost the same as deorbit.

[Nibb31]

There is no way to "mothball" the station. The effort to keep it flying unmanned in a higher orbit is pretty much the same as operating it right now. You would need active station-keeping from a mission control center and regular repair flights. At a minimum, the station will need to maintain power, cooling, and internal pressure.

If you abandon it, eventually parts will fail: the solar panels have a limited lifetime, seals and fluids degrade, tanks will vent, insulation and coating will flake, CMGs will fail. Without power, it will lose attitude control and without propellant, MMOD avoidance manoeuvers will be impossible. Any leaks or mechanical failures will cause it to tumble, making future docking efforts difficult or even impossible. Combined with fatigue, gravity gradients and possible MMOD strikes, some parts might just break off. After a few decades, it will just be a dead shell floating in a cloud of debris and a hazard to future missions.

Edited February 16, 2015 by Nibb31

[K^2]

That seems unreasonably grim. Atmo is absolutely unnecessary. Dump it. Station keeping isn't necessary. Higher orbits have considerably less traffic. Especially, at that inclanation. Get it into a 15M x 15M, and all it could possibly ever collide with are a handful or Molniya sats. The odds of it happening any time in foreseeable future are not worth mentioning. Attitude stability is almost trivial. Get it aligned with gravity gradient, and it will stay that way. It's a sub-optimal orientation for solar power use, but who cares? So attitude control isn't needed either. We're down to power and heating/cooling. Equilibrium temperatures, while far from habitable, should stay within electronics tolerance range. And power, well, it'll last as long as it will last.

I wouldn't expect the station to last past a decade. It could last longer, but it's likely to last less. And then, it will be a pile of debris. But I wouldn't classify it as a hazard because, again, this wouldn't be exactly a useful orbit. So it literally costs us nothing to keep it there. Even if it's going to serve absolutely zero purpose and just floats about as a pile of junk, there's just no reason not to keep it. And if we happen to make good use of it for however many years it manages to keep functioning, that's just gravy.

[Nibb31]

I'm not sure what use it would be once you have powered it down and dumped the atmosphere. It won't be visitable. Most of the equipment inside will by permanently destroyed by the vacuum and temperature. Gravity gradient is a pretty weak force for station-keeping, so pretty much anything could mess it up, including a leak from a pressurized fluid line or an MMOD strike.

Except for melting it down for scrap metal in 100 years, I really don't see what the point would be. And I'm pretty sure that it takes more dV to boost it into a 15Mx15M orbit than deorbit over the pacific.

[K^2]

Alright, yeah, 15M is a bit much. 5M would be only a touch more fuel than a clean de-orbit, though. And that's still almost clear of any other sats.

And while it'd be nice to mothball the station in a way that allows it to be quickly brought up to habitable state, just to keep it for emergencies, it's not strictly necessary. Yeah, there's a chance that it will expire or get knocked out of alignment by something. Might even have a leak that will cause it to spin up until it falls apart. But if it doesn't, you'd get to keep using the station for whatever observation and comm caps it would still have unmanned, and it might make a nice museum piece some day. I'd like to think we'll get capability to retrieve some old space ships in the future the same way we do with sunken ships today. Why throw out something that's such a big part of space exploration history? That's really the main point here. Save it if it can be saved for "free".

[shynung]

Disregarding the price (for now), is there any sense in using acetylene (C2H2) as rocket propellant, either plain or in a mix?