3 ms·
"[E]nergy to get a spacecraft to orbit? It's comparable to sending a 747 over the Atlantic." [citation needed] I have not done the math, but I find this quite
by gvb 17y ago
"[E]nergy to get a spacecraft to orbit? It's comparable to sending a 747 over the Atlantic."
[citation needed] I have not done the math, but I find this quite improbable.
The space shuttle has two SRBs with one million pounds of solid propellant each plus more than 500,000 gallons of super-cold liquid oxygen and liquid hydrogen.
http://www.nasa.gov/centers/kennedy/about/information/shuttle_faq.html#14 http://www.nasa.gov/centers/kennedy/about/information/shuttl...
The 747-8I has 64,225 U.S. gallons of jet fuel.
http://en.wikipedia.org/wiki/Boeing_747#Specifications http://en.wikipedia.org/wiki/Boeing_747#Specifications
According to http://www.convertunits.com/from/gallon+%5BU.S.%5D+of+naphtha+type+jet+fuel/to/joules http://www.convertunits.com/from/gallon+%5BU.S.%5D+of+naphth..., one gallon of jet fuel contains 133.92e6J, so a full fuel load on the biggest 747 is 8.6e12J.
According to somebody google found, the energy to get the shuttle into orbit is 1.17E11J, but that is just the potential and kinetic energy, neglecting the losses due to air resistance, etc.
http://www.physicsforums.com/showthread.php?t=229835 http://www.physicsforums.com/showthread.php?t=229835
http://xkcd.com/669/ http://xkcd.com/669/
- stcredzero 17y ago8.6e12J is indeed comparable to 1.17e11J. Thanks. I remembered that from a Robert Zubrin book.
- gvb 17y agoI agree that 8.6e12J is comparable to 1.17e11J, but the energy required to flying a 747 in real life is not comparable to the potential + kinetic energy of a shuttle, neglecting all losses required to achieve that potential + kinetic energy. In particular, two million pounds of SRB propellant plus more than 500,000 gallons of liquid oxygen and liquid hydrogen is not comparable to 64,225 U.S. gallons of jet fuel.
- stcredzero 17y agoThe point is that marshaling energies of that magnitude is actually pretty routine for our culture. In particular, two million pounds of SRB propellant plus more than 500,000 gallons of liquid oxygen and liquid hydrogen is not comparable to 64,225 U.S. gallons of jet fuel. In particular, you are acting as if the fundamental problem is represented by the Shuttle. That's just one particular configuration of one possible solution. What you're doing would be like someone from the early 1900's showing the in-feasibility of the performance envelope of a 747 by quoting the stats of a Curtiss biplane. Abandon the idea that you have to use chemical propulsion, or that you have to carry your own power, or even your own reaction mass, and you get fantastic improvement. Here's what you get when you only keep doing the 3rd thing: http://www.niac.usra.edu/files/library/meetings/fellows/mar04/897Kare.pdf http://www.niac.usra.edu/files/library/meetings/fellows/mar0...