Elon's Rocket

[Hell Razor5543]

How polluting rockets are is dependant on the fuel they use. For example, the Saturn V used hydrogen and oxygen, so they produced water as a waste product.

[Mandrake]

Wonder how many environmentally friendly electric vehicles Mr Musk has to sell in order to counter the pollution he's chucking out with each of his rockets ?
And before anyone gets annoyed - it's a serious question ! Just how polluting are rockets ???? It can't be that difficult to work out, I mean - it's not rocket science

How polluting rockets are is dependant on the fuel they use. For example, the Saturn V used hydrogen and oxygen, so they produced water as a waste product.

Actually not quite true. Only the upper stages of the Saturn V were Hydrogen. The main booster was RP-1, otherwise known as highly refined kerosene...

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

The Saturn V consisted of three stages—the S-IC first stage, S-II second stage and the S-IVB third stage—and the instrument unit. All three stages used liquid oxygen (LOX) as an oxidizer. The first stage used RP-1 for fuel, while the second and third stages used liquid hydrogen (LH2). The upper stages also used small solid-fueled ullage motors that helped to separate the stages during the launch, and to ensure that the liquid propellants were in a proper position to be drawn into the pumps.

For the recently retired space shuttle, the shuttle's built in boosters used Hydrogen, but the solid rocket booster used fuel called " Ammonium Perchlorate Composite Propellant":

The rocket propellant mixture in each solid rocket motor consisted of ammonium perchlorate (oxidizer, 69.6% by weight), atomized aluminium powder (fuel, 16%), iron oxide (catalyst, 0.4%), PBAN (binder, also acts as fuel, 12.04%), and an epoxy curing agent (1.96%).[7][8] This propellant is commonly referred to as Ammonium Perchlorate Composite Propellant, or simply APCP. This mixture gave the solid rocket motors a specific impulse of 242 seconds (2.37 km/s) at sea level or 268 seconds (2.63 km/s) in a vacuum.

The main fuel, aluminum, was used because it has a reasonable specific energy density of about 31.0 MJ/kg, but a high volumetric energy density, and is difficult to ignite accidentally.

The propellant had an 11-point star-shaped perforation in the forward motor segment and a double-truncated-cone perforation in each of the aft segments and aft closure. This configuration provided high thrust at ignition and then reduced the thrust by approximately a third 50 seconds after lift-off to avoid overstressing the vehicle during maximum dynamic pressure (Max Q).[7]

The Falcon 9 and Falcon Heavy rockets both use RP-1 (Kerosene) like most other rockets these days so its a fair point that it causes pollution as Kerosene is not a clean burning fuel.

What's interesting is that with the BFR they have decided to switch to liquid Methane as the fuel, despite no commercially flying rockets having ever used it before. (It has only be tried in a couple of prototypes on test beds)

There are two main reasons from what I've read - probably the biggest one is the ability to manufacture Methane on Mars as mentioned earlier - without being able to do this a round trip would be impossible. It's not feasible to manufacture Kerosene from what is available on Mars.

A second benefit is it is much cleaner burning, and that fits in with their whole reusability of rockets concept. Kerosene as a fuel leaves deposits in the injectors in the motor that eventually have to be cleaned out - so reusability is limited by having to strip down and clean the motors. Whether they have to do that after every flight or after a few flights I'm not sure, but the point is it's a significant maintenance burden to have to strip down and clean the motors for reuse, especially if you're somewhere like the moon at the time!

Methane is clean burning with the only byproducts being water vapour and CO2, and does not clog up the motors with gunk, so theoretically the motors can be reused time and time again simply by refuelling them, without any maintenance or strip downs - a massive cost and time savings on earth, and more or less essential on the moon or mars where you don't have the facilities to be overhauling the motors...

As a side effect, the only "pollution" produced by a Methane fuelled rocket is CO2 - but since it takes CO2 to make Methane in the first place (if you manufacture it) and it is already available in the carbon cycle in places such as waste dumps, farting cows etc, you could do it in a carbon neutral way, so Methane does seem like the clean but practical rocket fuel of the future.

Methane gives many of the advantages of Hydrogen as a fuel in terms of performance and cleanliness, but without the handling and practical problems like metal embrittlement, extremely low cryogenic temperatures required (that require bulkier insulation etc) so seems to hit a sweet spot between RP-1 and Hydrogen. I've been reading up on it and its quite interesting.

If they get the BFR doing grasshopper jumps next year like they're planning to it will be the first full scale working, flying rocket to use methane as a fuel. They certainly do like to push the boundaries of what has been done before...

[Gibbo2286]

I always wonder if all this thrust is moving Earth out of its natural position in space, I know it's has huge mass but tiny thrust motors can move a lot of mass in a vacuum.

[411514]

I always wonder if all this thrust is moving Earth out of its natural position in space, I know it's has huge mass but tiny thrust motors can move a lot of mass in a vacuum.

That's why I avoid accelerating too hard when driving east - don't want to make the day any longer.

[CitroJim]

I always wonder if all this thrust is moving Earth out of its natural position in space, I know it's has huge mass but tiny thrust motors can move a lot of mass in a vacuum.

That's why I avoid accelerating too hard when driving east - don't want to make the day any longer.

I wish I could have given this post 10 likes rather than just the one... Really made me laugh out loud Sam

[411514]

made me laugh out loud

I had better pretend I wasn't being serious then

[myglaren]

[NewcastleFalcon]

The explanation.... if you don't know Star Trek episodes intimately


Regards Neil

[NewcastleFalcon]

I watched "The Search fior a new Earth" a BBC 4 Documentary shown in September 2017 until I literally fell asleep, but it did have some interesting ideas with respect to space travel particularly in relation to plasma engines, and laser propelled spacecraft with sails, and the sheer human challenge, both physically and mentally, of spending months or even years travelling .

There is something quite comforting about using "sailing ships" to explore space using light, solar winds, planets magnetic fields etc. It ties in with how sailing ships opened up the exploration of planet earth in the past. I guess we have rowed in our metaphorical boats to the moon and back so far, but need something faster to explore a little further. The first journey to Mars is going to be considerably more challenging than the 4.00pm Megabus out of London to Newcastle and that requires a great deal of human endurance to combat the crushing boredom in its own right

Wiki as ever has a few pages on the subject
https://en.wikipedia.org/wiki/Plasma_propulsion_engine
https://en.wikipedia.org/wiki/Magnetic_sail
https://en.wikipedia.org/wiki/Solar_sail
https://en.wikipedia.org/wiki/Electric_sail

Regards Neil

[myglaren]

Probably due to something I was reading when I bought this, I always associate 'Solar Sails' with:



The guitar principally, most noticeably at 1' 49"

[van ordinaire]

Long before StarTrek there was "The Day the Earth Caught Fire" - wasn't that the basic premise?

Just one thing caught my attention about this latest variant of firing old cars off aircraft carriers by catapult, was the reference to "one of his old roadsters".

[CitroJim]

was the reference to "one of his old roadsters".

Old? To me that's a positively brand-new car...

'Old' in my book is pre-1960s at least - i.e. before I was born...

[Hell Razor5543]

Well, Top Gear did try to make a shuttle, using an old car;

[miked]

Is it a bug, or feature? We are all a number.

The Falcon heavy launch was the best thing i've watched ever, since the first space shuttle took off when our primary school headmaster stood us around a TV and said watch this.

I stayed up late (OK, 9ish) and I didn't know which way it was going to go. Could have done without the cheering crowd but seeing the two booster rockets land back together was epic.

Am I allowed to recommend a book? Graham Swinerd, how spacecraft fly. I can answer my kid's when they ask "Why isn't it going straight up" etc.

[NewcastleFalcon]

Am I allowed to recommend a book? Graham Swinerd, how spacecraft fly. I can answer my kid's when they ask "Why isn't it going straight up" etc.

Of course you can! Its the food and drink of The Pickled Egg Library Believe me FCF members have deposited all sorts of stuff in there. My last deposit was this, in other words anything goes!

Another deposit, more of a short coffee table browse for those fascinated with the early days of Ceefax

http://www.bbc.co.uk/news/magazine-20032531

Regards Neil