Topic: SpaceX and the prospects of Mars colonization. - page 7. (Read 31904 times)

This is a good question... a difficult one to visualize without computer models. The heat is dissipated by not even reaching the rocket skin. It is dissipated in the steam. However...

In a simple V8 car engine that has a 9.5:1 compression ratio, in optimum conditions, a wide-open burn of the air/fuel mixture in the cylinders produces a temperature in excess of 5,000 degrees F. But that is under some reasonably high pressures. The heat drops off substantially as the piston moves; some of the heat is absorption into the piston head, the engine head, and the cylinder walls. Most of it goes out the exhaust system.

What are the burning gasses that are so hot in the V8 engine? In optimum running conditions, they are essentially only water (steam) and CO2 (gasoline burns into these).

What amount of gasoline does it take, say, for a 350 cu. inch V8 engine to reach that heat? The droplet of gasoline per cylinder per double stroke would be less than a 0.2 inch diameter sphere of fuel per cylinder. The resulting steam and CO2 are slightly more than the size of the gasoline, because of the air added to burn the gasoline.

The point is that there is a lot to take into consideration. Look at the amount of fuel it takes to get the rocket up there in the first place. There is some heating of the skin of the rocket on the way up. But most of the fuel is used to lift.

Since there is no lift action required on the way down, I would think that the amount of water to make the steam to cool the skin would be a lot less than the amount in the tanks on the way up.

Intriguing question. Did Musk run the simulations? Or is he only talking at this stage of the game?

Because for the vehicle to slow down, it has to dissipate that heat. Musk wants to do exactly what you are guessing at. But take the total kinetic energy, and see how much water would be changed to steam to take up that amount of energy, and it's about 2000 tons of water.

Maybe I'm not thinking about this clearly, but, when they use liquid hydrogen and liquid oxygen as fuel, the result coming out of the rocket engine is water... in vapor form, of course. My question is, why wouldn't a returning rocket be able to ride on a thin layer of water vapor?

If the rocket descended nose first until it almost reached the ground, why not spray a thin stream of water out of the tip of the nose? This water would be turned into "steam" immediately because of the friction. Then it would envelope the whole rocket as it slid by, taking up the extra heat, and sliding it past the falling rocket.

When the rocket neared the ground, thrusters would invert it so that it could land on its main engines... or whatever other way it was supposed to land.

Anyway, isn't that a saltshaker in the picture, above?

Fake X wont exist for long Earth is flat .

Once the revolution kick starts even dumb morons will know the truth.

I tried to post this but seem to have messed up a prior post.

Anyway the idea was to use stainless steel with water cooling the skin for the heat of re entry. But using numbers for the Space Shuttle, that would take the better part of 2000 kilotons of water.

Double that for a return from Mars or the Moon.

Actually people need to be fired over this. Basic procedures followed at any airport, such as tying the thing down with ropes, would have prevented the mishap.

^^^ And you have proof of this, right? LOL!    

EDIT: With the thing lying down, it would be much easier to use a tape-measure to measure it.

^^^ NASA lies about the height of their vehicle assembly building so flat earthers can't use the numbers they provide to prove the earth is not a globe with P900 photos from the highway.

NASA is the source of the "official" atmosphereic refraction tables used by "modern science" and if they claim refraction is causing the building to be lifted up over the curve they'll contradict their own numbers, so they lie about the height.

Why of course! There are no winds to worry about in space

Too bad they didn't use a hangar to protect it, that is precisely why NASA has that gigantic vertical building near the launchpad... A spacecraft meant to be launched into space is expected to be as light as possible, so its no wonder that, if left outside, a 50mph wind could mess it up.


Maybe this mockup was quite empty, perhaps with more stuff inside it would be harder to tip over (or they would build an underground silo in Mars?).

I'm really glad that space winds aren't this strong.


SpaceX's giant rocket ship was blown over and damaged by powerful winds in Texas --




And repairs will take weeks? That's longer than it took to build the whole thing from scratch. Are these guys so demoralized that they can't repair it any faster? What are they going to do if it tips over on Mars?

Be careful, there are two things named Orion. First is the conceptual nuclear rocket, which was never built. Second is the current generation Orion deep space vehicle. This thing is a genuine class act and very impressive. (SIDE NOTE: Trump was pushing NASA to send 2 men on a cis lunar orbit in 2019, but NASA said they need more time, and that 2020 was possible. I have to laugh....let the democrats try to beat Trump as he takes us "Back to the Moon" right in the election cycle...)

https://en.wikipedia.org/wiki/Orion_(spacecraft)

What I was trying to impress is a very simple fact, that math and physics RULES, not what Musk says. With an understanding of some not-difficult level it's rather easy to think these things out.

As for nuclear, nuclear power is used routinely in spacecraft, "nuclear batteries." Apollo left polonium generators on the surface powering instrumentation, the Russians used plutonium batteries (and we do also). You would not have robotic spacecraft going to Saturn or Pluto without these.

Nuclear power plants such as NIRVA are totally practical for long distance travel such as to Mars and beyond. Again, physics rules. Mission profile is compared to possible power methods, then one is picked.

just like you see them using concepts and ideas others proposed decades ago.

More correctly, math and physics of spaceflight have not changed.

"Rapid Unintentional Disassembly" is a tradition (baptism of fire?) of all agencies and companies that have embarked in this business known as "rocket science". NASA and the Soviets had a long series of catastrophic failures, and even the meticulous europeans once uploaded the wrong software to a rocket that was perfectly fine (Arianne 4 parameters into Arianne 5, IIRC); and everyone learns from those mistakes. Even Von Braun with the Nazis had a lot of failures with the V2, there was this hilarious comment of a general about its usefulness as a short range artillery weapon (when failing and blowing spectacularly at/near the launch site.

But then, after so many failures they did it:



With a historic landing, SpaceX launches new age of spaceflight

And this is their merit, one of many, and I expect them to keep delivering and return us to an age were we can dream again.

It is nice that brilliant people planned and hoped to realize this within NASA or other State agencies, but what is the value if it remains buried behind eternal bureaucracy and budget cuts? Yes, Orion could have performed this decades ago, but they didn't do it. In fact there is a lot of trouble just to send anything "nuclear", even a small passive generator for deep space missions, let alone using directly the energy from controlled nuclear blasts.

At least these people are opening a path, and i hope they can make it sustainable. I'm sure if an idea doesn't seem feasible, they will change it to one that could. From my fuzzy memory i think Elon was once asked about the ferry loop idea, IIRC he said something along the lines of: "that is not ruled out". I might be mistaken, but if it makes more sense from their point of view, they will reach to it one way or another, just like you see them using concepts and ideas others proposed decades ago.

Anything one wants to ask about traveling to Mars could be asked to a number of people who have studied the problem intently for decades, which Musk has not. That's why he's capable of making simple errors such as those we discussed. There are many truly brilliant people holed up in NASA and universities; you have never heard their names and likely never will.

Radiation protection is best handled by shortening the trip; that is accomplished by ion engines, which can reduce a 8 month trip to 40 days. Using such an engine, acceleration is low, like 1/1000 of a G. Acceleration force on the airframe such as you mentioned, capable of going to space from earth and capable of descending to Mars, is perhaps 6G. That is a difference of 6000 and you can directly note a difference of 6000 in the weight of structural support in the spacecraft.

For a ship headed to Mars, that 5999/6000 savings in structure translates directly to more payload, humans, supplies, etc. This is the primary reason we separate a "spacecraft" from a "launch vehicle." Dead weight and fractions of dead weight to useful payload.

Such ion engines require electrical power, most likely nuclear.

A good reference book, available free online is Dr. Robert Zubrin "The Case For Mars."

http://www.ifa.hawaii.edu/%7Emeech/a281/handouts/mars_case.pdf

A coat of paint and a little extension and it's ready to go!

That would have been a good question to him in that Reddit AMA about SpaceX and Mars. Of course I see the merit, i have read about that idea before, and see it as perfectly valid. I also consider that loop ferry sort of like a moving space station. Perhaps shielding against the sun radiation bursts could be one problem, the ISS wasn't designed for that but another station/spacecraft could. If SpaceX's plan goes ahead, that very ship in the proposal could be doing the loops as well.

Almost nothing in SpaceX is original, they simply made things commercially possible after so much government stagnation. That's quite a feat, for someone who was just another geek programming in a garage like some people here, who became millionaire (by selling Paypal) and instead of sitting on his money, decided to push things for humanity realizing dreams considered "impossible" by most...

FYI, the debate over "keeping it all together" started WITH the Apollo program, and physics/math defeated it.

But the concepts continued, and found advocates during the 1980s. In the 1990s BMDO created the Delta Clipper test vehicle.

https://www.youtube.com/watch?v=o2sHf-udJI8

That used four RL10 h2/o2 engines as a proof of concept. That's where these ideas come from, they do not originate with SpaceX.

With Mars mission profiles though, I can guarantee you that the concept drawing you showed me is not feasible and the opposite of optimum. Let's just say it's ridiculous. Elon Musk is not going to open up Mars to humanity with bad ideas. But who knows, maybe someone will talk some sense into him.

I am curious, though. Why would you not see the merit in a true spacecraft, something that could loop continually  between Mars and Earth? It could have artificial gravity, use ion propulsion, be extremely lightweight as it would never be stressed by gravitational fields, and in every way be optimized for deep space extended travel. As an example of this, consider that you could attach a suitable propulsion unit, and send the ISS to mars and back.

Then you would have ferry style transports at each planet.

In that case there is nothing to do but wait until they deliver. Do you think SpaceX doesn't know about the advantages / disadvantages of staging? I see them using stages in their current rockets, up to the falcon heavy...

On the other hand, how many years have passed since the Apollo program? You'd think some advances have been made in all these years. They want to reuse parts, yet they can't recover the second stage in their current rockets. Perhaps keeping it all together allows them to achieve that goal?

In my opinion, they are going to waste more fuel by not using stages, but don't forget they don't plan to go straight away, they plan to refuel in orbit so the fuel they need is only to reach orbit, not Mars. The more efficient engines for vacuum/light atmosphere are already attached to the spacecraft.

Once (if) these concepts become reality, we can see if they were wrong or not. At the very least, they have been delivering results so far.

Some quick back-of-the-envelope calculations tell me this will burn up on re entry 100% reliably.

You are wrong. There is a spacecraft planned, its what goes on top of the bfr "Super Heavy"... Called "Starship":



In this CGI picture the launch vehicle "Super Heavy" is returning back to earth while the spacecraft "Starship" goes to an earth orbit to refuel with a similar shaped (but fuel only) vessel; to then carry on with its mission carrying people and cargo.

Here is the official site of their plans: https://www.spacex.com/mars
And here are more details of the spacecraft: http://spaceflight101.com/spx/its-spaceship/

There are such incredible amounts of funds that go for projects in science and the military, without anybody being able to pinpoint exactly how they are used, that we might have had bases on Mars long ago, using this... https://newatlas.com/orion-project-atom-bomb-spaceship/49454/.