Re: How Rockets Differ From Jets

tomcat,
There's nothing unimpressive about our existing shuttles, nor about
your proposed Spaceplane. They're certainly big items, extremely
complex and at least our shuttles remain relatively heavy for their
usable volume even when bone dry, not to mention spendy as all get out
to have been created in the first place, as well as damn near as spendy
to keep reusing, especially spendy if you'd care to put any price tag
on human life as well as for their horrific environmental impact upon
mother Earth that goes far beyond that which is launch contributed. The
biggest technical problem remains their rate of LH2/fuel and
O2/oxidiser consumption is so horrific that the ET needs to be several
times the volume of the entire shuttle itself, and even then it needs
those two extremely powerful SRBs/SBRs to boot. Therefore, short of
using an H-Bomb as a method of getting yourself into space, the shuttle
is next in line to being nearly as spendy per kg and damn near as
lethal as any form of metro transportation gets.

Here's what seemingly everybody already knows, although topic newcomers
might be amused to learn;

http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/srb.html
The two SRBs provide the main thrust to lift the space shuttle off the
pad and up to an altitude of about 150,000 feet, or 24 nautical miles
(28 statute miles). Each booster has a thrust (sea level) of
approximately 3,300,000 pounds at launch. The two SRBs provide 71.4
percent of the thrust at lift- off and during first-stage ascent.
Seventy five seconds after SRB separation, SRB apogee occurs at an
altitude of approximately 220,000 feet, or 35 nautical miles (41
statute miles). SRB impact occurs in the ocean approximately 122
nautical miles (141 statute miles) downrange.

Each SRB weighs approximately 1,300,000 pounds at launch. The
propellant for each solid rocket motor weighs approximately 1,100,000
pounds. The inert weight of each SRB is approximately 192,000 pounds.

Rocketdyne SSME @~500,000 lbs thrust (Vacuum)
http://www.boeing.com/defense-space/space/propul/SSMEamaz.html
http://www.boeing.com/defense-space/space/propul/SSME.html
SSME can attain a maximum thrust level (in vacuum) of 512,950 pounds
which is equivalent to greater than 12,000,000 horsepower.

http://www.airliners.net/discussions/military/read.main/37552/
Each SSME burns 920 lbs/s(417 kg/s) of LOX and 155 lb/s(70 kg/s) of
LH2. At 100% power, that's per each and every second per engine.

http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-mps.html
The main engines can be throttled over a range of 65 to 109 percent of
their rated power level in 1-percent increments. A value of 100 percent
corresponds to a thrust level of 375,000 pounds at sea level and
470,000 pounds in a vacuum. A value of 104 percent corresponds to
393,800 pounds at sea level and 488,800 pounds in a vacuum; 109 percent
corresponds to 417,300 pounds at sea level and 513,250 pounds in a
vacuum.

The 17-inch-diameter feed line permits liquid oxygen to flow at
approximately 2,787 pounds (1264 kg) per second with the SSMEs
operating at 104 percent or permits a maximum flow of 17,592 gallons
per minute. The liquid oxygen tank's double-wedge nose cone reduces
drag and heating, contains the vehicle's ascent air data system (for
nine tanks only) and serves as a lightning rod. The liquid oxygen
tank's volume is 19,563 cubic feet. It is 331 inches in diameter, 592
inches long and weighs 12,000 pounds empty.

The liquid hydrogen feed line flow rate is 465 pounds (211 kg) per
second with the SSMEs at 104 percent or a maximum flow of 47,365
gallons per minute. The liquid hydrogen tank is 331 inches in diameter,
1,160 inches long, and has a volume of 53,518 cubic feet and a dry
weight of 29,000 pounds.
-

Overall, a space shuttle main engine weighs in at approximately 7,000
pounds, but it also requires a great deal of extra structural
spacecraft attributes and loads of secondary/external related circuitry
and elements in order to accommodate each engine, such as the massive
ET interface plus the Helium/LXO internal tankage, thus perhaps a tally
of 10,000 pounds each represents 3X 10,000 = 30,000 lbs(13,608 kg), and
obviously a good deal of sheer volume is allocated.

Any good sized (new and improved) Spaceplane/shuttle would likely need
at least 6 if not an interplanetary dozen of these SSMEs, plus at least
4 of those SBRs for getting past the first 150,000', thus 2~4 times the
ET volumes of LH2/LXO unless the SBRs contribute a whole lot more than
75% of the total package thrust. The only alternative is to construct
everything as much as possible out of basalt and CNT composites, so
that we might get the entire package back into the realm of using just
two SRBs/SBRs and perhaps not more than the original 3 SSMEs, which
might then enable a payload of 100 tonnes getting delivered to a
greater than LEO altitude of 350+km. Unfortunately, the existing
cargo-bay design needs to be half again as wide and nearly twice as
long, meaning less room for accommodating those conventional SSMEs.

Just cutting the SRB inert mass in half should more than do the trick,
tossing in another similar reduction in shuttle and ET inert mass by
50% is just icing on the cake that'll get whatever delivered in style
with margin to spare, perhaps even enough margin for a lunar mission
involving our establishing the LSE-CM/ISS before China, Russia or
ESA/India beats us to the punch. Of course, these lighter weight SRBs
and even the ET might not be quite as reusable, but then reusing such
items as before has created come rather serious compromises that have
more than cost as much as going with the 100% disposable plan of
action.

LRn222, use it or lose it

on the other hand, if the Radium-->Radon-->ION can accomplish what I'm
thinking it can, in which case the massive ET can be replaced with
something that's not even 10% the volume. The shuttle itself would have
an array of ion thrusters that I'm wishful thinking together shouldn't
weigh half as much as one SSME, but even if at 10,000 lbs worth and yet
affording the same if not greater net thrust as 3 SSMEs is still 3:1
better off. Therefore, an internal capacity of spare LRn plus having an
onboard Radium-->Radon breeder reactor for creating a fresh supply of
Radon on the fly that isn't going to take up all that much volume, nor
demanding the degree of containment and thus greatly improving the
overall safety while making all such things as Spaceplanes lighter as
well as simpler to own and operate, as well as a whole lot less
polluting.
~

Kurt Vonnegut would have to agree; WAR is WAR, thus "in war there are
no rules" - In fact, war has been the very reason of having to deal
with the likes of others that haven't been playing by whatever rules,
such as GW Bush.
Life upon Venus, a township w/Bridge & ET/UFO Park-n-Ride Tarmac:
http://guthvenus.tripod.com/gv-town.htm
The Russian/China LSE-CM/ISS (Lunar Space Elevator)
http://guthvenus.tripod.com/lunar-space-elevator.htm
Venus ETs, plus the updated sub-topics; Brad Guth / GASA-IEIS
http://guthvenus.tripod.com/gv-topics.htm

.

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