Topic: FAO: Syntax
Metæ started this discussion 12 years ago #35,232
You know a lot about satellites: how many bottle rockets do I need to strap to my car to make it into low earth orbit?
Thanks.
Thanks.
Syntax joined in and replied with this 12 years ago, 38 minutes later[^] [v] #484,808
The question is more for a Rocket Science guy. I have worn the hat as launch manager just a few tymes but of course did not design the Rocket. Did build many a rocket as a kiddlet with much success. Never did get a mouse back to earth n still working.
I will save you a bit of trouble with the figuring it out. Books tell you about escape velocity which can be misleading. Usually one assumes escape velocity as 11 km/s. But for a LEO orbit one can play a energy saving protocol and do the launch in two phases usually with one rocket on top of the other. First one takes you to say 280 to 380 KM or so which only takes about 7.5 to 8.5 km/second. Think of this as straight up which of course its not really ...more of an arc but also somewhat vertical. You want to halt rocket power at this point then you jettison the 1st rocket. Tilt the rocket to anything less then vertical by 15 or so degrees and fire the 2nd rocket. Energy savings cause you do not want escape velocity and now you are in orbit. Not forever but then again what is forever.
A quick look at math
E = GMm(1/r-1/(2a+2r)
G = gravitational constant
M = mass of Earth
m = mass of car
r = radius of Earth
a= altitude of orbit
Look up the correction term for earth rotation and apply to result.
Up there in LEO orbit say 8.0KM/sec takes about 32,700,000 joules per Kg so you just convert car weight to KG. I have no clue how much E you get from a bottle rocket but easy to look up and of course there might be a minor issue re having to use a horrid number re the short burn you get but you can have fun with the Math. You can have some fun with Newton's law of gravitation which is basic calculus.
Quick thought says to me hey you could scale down the car to a model car and have more success but no one will be impressed at results.
I will save you a bit of trouble with the figuring it out. Books tell you about escape velocity which can be misleading. Usually one assumes escape velocity as 11 km/s. But for a LEO orbit one can play a energy saving protocol and do the launch in two phases usually with one rocket on top of the other. First one takes you to say 280 to 380 KM or so which only takes about 7.5 to 8.5 km/second. Think of this as straight up which of course its not really ...more of an arc but also somewhat vertical. You want to halt rocket power at this point then you jettison the 1st rocket. Tilt the rocket to anything less then vertical by 15 or so degrees and fire the 2nd rocket. Energy savings cause you do not want escape velocity and now you are in orbit. Not forever but then again what is forever.
A quick look at math
E = GMm(1/r-1/(2a+2r)
G = gravitational constant
M = mass of Earth
m = mass of car
r = radius of Earth
a= altitude of orbit
Look up the correction term for earth rotation and apply to result.
Up there in LEO orbit say 8.0KM/sec takes about 32,700,000 joules per Kg so you just convert car weight to KG. I have no clue how much E you get from a bottle rocket but easy to look up and of course there might be a minor issue re having to use a horrid number re the short burn you get but you can have fun with the Math. You can have some fun with Newton's law of gravitation which is basic calculus.
Quick thought says to me hey you could scale down the car to a model car and have more success but no one will be impressed at results.
Anonymous C joined in and replied with this 12 years ago, 1 hour later, 1 hour after the original post[^] [v] #484,830
Anonymous D joined in and replied with this 12 years ago, 1 hour later, 2 hours after the original post[^] [v] #484,845
Syntax replied with this 12 years ago, 9 hours later, 12 hours after the original post[^] [v] #484,896
@previous (D)
Why b upset about LEO orbits? No GPS without No useful Cell communications in Space (ground2space n back) Time delay using GEO's is horrid just horrid arwful and small cell phones Impossible re power needed to get to the GEO.
Why b upset about LEO orbits? No GPS without No useful Cell communications in Space (ground2space n back) Time delay using GEO's is horrid just horrid arwful and small cell phones Impossible re power needed to get to the GEO.
The Captain !PundosRBSM joined in and replied with this 12 years ago, 1 hour later, 13 hours after the original post[^] [v] #484,908
Anonymous D replied with this 12 years ago, 2 minutes later, 13 hours after the original post[^] [v] #484,909
Syntax replied with this 12 years ago, 1 hour later, 15 hours after the original post[^] [v] #484,919
Anonymous F joined in and replied with this 12 years ago, 48 minutes later, 15 hours after the original post[^] [v] #484,927
Syntax replied with this 12 years ago, 53 minutes later, 16 hours after the original post[^] [v] #484,933
@previous (F)
Thanks rare I rite and read later n understand wot I rote - anyway I thought I wood take a look at Bottle Rockets for the fun of it - used to make home made ones out of Gunpowder (homemade)
Wiki says
Gunpowder contains 3 megajoules per kilogram - For comparison - energy density of gasoline is 47.2 megajoules per kilogram.
> LEO orbit say 8.0KM/sec takes about 32,700,000 joules per Kg
10,900,000 Kilos of Gunpowder LOLOLOL Me thinks a re think may be necessary
Reminds me - back as Kiddlet I wood take a coffee can and splash in some Gasoline and invert - Used a spark gap fuse - Major super high in altitude launch (often at wrong angle but can sure went far)
Lots more Energy from Gas which a car already has in Tank
Thanks rare I rite and read later n understand wot I rote - anyway I thought I wood take a look at Bottle Rockets for the fun of it - used to make home made ones out of Gunpowder (homemade)
Wiki says
Gunpowder contains 3 megajoules per kilogram - For comparison - energy density of gasoline is 47.2 megajoules per kilogram.
> LEO orbit say 8.0KM/sec takes about 32,700,000 joules per Kg
10,900,000 Kilos of Gunpowder LOLOLOL Me thinks a re think may be necessary
Reminds me - back as Kiddlet I wood take a coffee can and splash in some Gasoline and invert - Used a spark gap fuse - Major super high in altitude launch (often at wrong angle but can sure went far)
Lots more Energy from Gas which a car already has in Tank