That paint job...
reminds me of this.
NASA’s potentially Mars-bound spaceship is set for its first test flight today, with a 70 per cent chance of good weather for the blast-off. Orion on the launch pad fuelling up The space agency has just finished fuelling up Orion, which it hopes will be the successor craft to Apollo and will carry astronauts to the Moon, …
If you're coming down from orbit, then you'll be going just a bit less than orbital velocity of 17,500 mph.
Earth escape velocity is about 25,000 mph. That's what you need in order to get to the Moon or Mars. As it takes lots of fuel to get that, it's too difficult to carry enough to slow down much on the way back. Hence you brake using the atmosphere.
From memory you only pull about 3G on normal re-entry, whereas the astronauts returning from the Moon had to put up with something like 6. And Apollo 13 was more, because they got the entry angle slightly wrong.
Obviously you want to go to Mars as quickly as possible, so there's a balance between how much you accelerate to speed up the trip, how much fuel you can take to slow down - and how much pain you're willing to put up with on aerobraking. I guess this is another reason that they want to take their Earth re-entry craft with them all the way to Mars, as it woulld take too much fuel to be able to slow back down to orbital velocity and rendevous with one (the craft may be lighter than the fuel otherwise needed). Also the Orion is a lifeboat, as you can abort directly to Earth if the rest of the Mars ship breaks down. NASA presumably decided the AA were too expensive...
but they do all this amazing slingshot actions with satellites to speed them up on their way off to the far reaches on the solar system...
can't they also factor in a similar way of slingshotting in a way that bleeds off speed so that eventually they end up just orbiting the earth. and can then drop in as a normal re-entry, or dock with the ISS and go home in the next supply shuttle or something.
it's going to add a lot of time to the mission i guess....
Funny you should say that PaulyV, when i was a nipper, we were told that the Moon had a gravity that was 'one third' that of the Earth. About 12 months ago i heard one of the BBC space correspondents say that the Moon has a gravity that is 'one sixth' that of Earth. Maybe the Moon has been on the Atkins?
"Or the Earth's gravity has increased; that is surely the only explanation for all the bathroom scales..."
That would certainly explain mine. I presume the atmosphere has thinned out a bit now, as well, so there is reduced air pressure - which might explain my slightly expanding stomach.
But for the AC - the Moon's gravity was 1/6 of Earths when I was a nipper. (I left school in the mid 1980s.)
"All the technical people they need to lanuch a rocket to the stars, in this case the Moon, and yet all it takes, once they're on the Moon is someone in the capsule to press a button and weeeeeeee they blast off for home.....unbelievable some might say."
Cherrypick some data, dismiss hundreds of support staff for the Apollo LEM flight in Houston, and then, yes, you can look it unbelievable.
The Apollo LEM went through most of the same preparations that any rocket goes through: years of planning, months of readying on Earth (fueling, charging, safing), huge numbers of personnel providing navigational support, and everything else. The difference is that a few days before the LEM's launch it was put on "hold" and stored pending astronauts pressing "a button." (Where "a button" means "going through long flight check lists of preparations to launch the ascent stage, including programming the LEM's computer based on the input of navigational teams on Earth to intercept the actual orbit of the Apollo CSM, which was not exactly the planned orbit.")
Or, if you like, you could compare the Apollo LEM to the liquid-fueled ICBMs of the era. Those also required relatively minimal preparation compared to a conventional launcher.
I wonder what type of fuel they used to blast off from the Moon for Earth back in the Sixties?
On earth they use Liquid Hydrogen, a volatile substance that has to be watched over by hundreds of technicians and ground staff and yet on the moon they need nobody....funny that.
Well, being no rocket scientist I don't know for sure, but it may have something to do with the fact that Earth's average atmospheric temperature is at least 288 kelvin, whereas in space it's only 3 (in the shade).
Given that liquid hydrogen is solid below 20 kelvin and gaseous otherwise, that might explain things.
"I wonder what type of fuel they used to blast off from the Moon for Earth back in the Sixties?"
The Apollo Service Module and both ascent and descent stages of the Apollo Lunar Excursion module used Aerozine 50 (a 50/50 mix of hydrazine and UDMH) and nitrogen tetroxide.
"On earth they use Liquid Hydrogen, a volatile substance that has to be watched over by hundreds of technicians and ground staff and yet on the moon they need nobody"
The Saturn V used kerosene and liquid oxygen in its Saturn IC first stage, then hydrogen and oxygen in its second (Saturn II) and third (Saturn IVB) upper stages.
The Delta IV used by Orion is unusual in that it uses hydrogen/oxygen for all of its ground (booster, core) stages. You typically want lower impulse engines like solids or kerosene/oxygen on the first stage for a couple of reasons. One, you shed weight quickly and thus reduce gravity losses during ascent. Two, you get more thrust from dense fuel motors than low density motors for a given engine weight. (The best hydrogen/oxygen engines manage a ~75:1 thrust-to-weight ratio, while SpaceX is flying kerosene/oxygen engines with ~150:1 thrust-to-weight ratios, and even the overbuilt F-1 engine of Apollo managed ~100:1.) Delta IV's engine selection was a compromise based on costs, engine availability, and engine simplicity.
Not really when you look at the different situations and engineering requirements.
Regarding Earth launch vs Moon launch engines, the situations are radically different on several counts. The overriding issue for Earth launches is the huge amount of delta-V (and thus fuel) you need to get into Earth orbit. That calls for high-efficiency fuels like hydrogen/oxygen, at least in weight-sensitive upper stages. The moon's delta-V launch requirements are radically lower, and the engineering impact of being so much further down the exponential Rocket Equation curve is fascinating: you don't need multiple stages to reach orbit; you don't need high thrust-to-weight ratios (so you can over-build and simplify your engines for reliability); and you don't need high-efficiency fuels.
On the other hand, NOT having hundreds of techs and engineers and a vast support infrastructure on hand for a launch from the lunar surface means you need to make compromises in the name of reliability. The Apollo LEM used toxic propellants that can be stored without heavy insulation and boil off that hydrogen and, to a lesser extent, liquid oxygen suffered. While the LEM could've used kerosene (or ethanol) and liquid oxygen (or hydrogen peroxide) with only modest storage problems, Aerozine 50 and nitrogen tetroxide had the advantage of easy ignition: they ignited when they touched each other. Weight limits meant the LEM could only have 1 engine, so it HAD to work without adding complicated ignition systems. Hence, toxic, hypergolic propellants were used. NASA has been trying to eliminate those propellants for decades, even suggesting overhauling the shuttles to use ethanol / oxygen. They're nasty enough that even Russia has taken steps to reduce the amount of hydrazine, UDMH, and nitrogen tetroxide it splashes across Siberia from spent stages.
In the past...heck, even now, in Russia...some rockets do use the Apollo LEM's propellants because of their simplicity and storability. They were the liquid propellants of choice for early ICBMs, but much-safer solid rockets replaced them. (They're storable without refrigeration, but a small corrosion leak between hypergolic, toxic propellants can turn a missile silo into a roman candle, or at least kill the technicians with their fumes. Hence: solids.) For civilian rockets that don't need to be stored in silos for years, you have additional options like kerosene/oxygen and hydrogen/oxygen, which give better performance without as much instant lung-burning death as the LEM's propellants.
"We're all going to be screwed when the KSP team implement re-entry properly."
Like an escort at a power tool convention. None of the behemoth interplanetary stacks I just aerobraked into Duna orbit had a decent reentry shield.
"At the moment, you can return from the Mün and slam into Kerbal at 3 Kps with a 90 degree angle and still survive."
At least the speeds are much lower than in reality. A few minutes of heating from 3kps to 100m/s wouldn't raise skin temperatures to the extremes that a normal Earth orbit reentry faces.
"No violence of the rocket motor,"
You stand near a launching LEM and tell me there's no violence. All rocket engine firings near a surface in a vacuum (on the moon) or a near vacuum (on Mars) have produced quite a bit of violence, scouring the surface and driving dust and light debris. The Apollo landers all had varying degrees of damage to their rocket nozzles and undercarriage from debris. The "sky crane" system of Curiosity was meant to protect the rover from debris kicked up the rocket blasts, but failed - Curiosity at least lost part of its mast-mounted wind speed system to a wire nicked by a rock.
"no 'heat bloom' as the capsule takes off for home"
Of course not. The Aerozine 50/nitrogen tetroxide mix scarcely produces visible flames in the atmosphere where there's other gases to heat up and cause side reactions with the combustion products. In a vacuum, you'd need to stare straight up the rocket nozzle to see a glow. With low resolution TV cameras used on the lunar surface to follow the launch, you're not going to see much of anything.
Aerozine 50/nitrogen tetroxide are quite similar to a number of other rocket propellants in their lack of "glow." I'm sure you've seen that alcohol flames are hard to spot, while hydrogen/oxygen fires also tend to be hard to see unless something else is caught in the combustion (like the skin of the Hindenberg or the ablative lining of Delta IV rocket engines). Supposedly, early rocket scientists working around H2/O2 rocket test stands would walk with a straw broom held in front of them to help detect a burning hydrogen leak - the broom would burst into visible flames if a hydrogen fire was encountered.
The problem with assuming that the **entertainment** industry actually makes the *movies* you watch completely and utterly accurate to the real world is that, well, the real world is horrendously boring to the vast majority of humanity. Then when reality comes along you make incorrect assumptions about what you believe you should have seen.
Me? I'm not an ass. I'm a grumpy old bastard.
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NASA already knows we're not going manned to Mars anytime soon, but the FOX public demands delusions. Until we solve the bone mass, iris detaching in mid trip issues and find a way to keep the new Martians supplied, it'll be a death trap (This is all published info too).
Love the Reality Show angle too, life is turning into one since you can't believe anything anymore !
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