On Jan 26, 9:33*am, Robert Clark wrote:
On Jan 19, 5:56*pm, Robert Clark wrote:

...This page gives the specifications of the Ares I:

SpaceLaunch Report - Ares I.http://www.spacelaunchreport.com/ares1.html

*The gross weight including payload is given as 912,660 kg and the
gross weight of the first stage as 732,550 kg. So the gross weight of
the Ares I second stage plus payload is 180,110 kg.
*Then the gross weight for the 55,442 kg dry weight of the
reconfiguredshuttle, plus 300,000 kg propellant load, plus 180,110 kg
second stage and payload is 535,552 kg, 1,178,214 lbs. But the 3 NK-33
engines I was suggesting to use only put out a total of 1,018,518 lbs.
of thrust at sea level. For this purpose you would need a fourth
NK-33. The dry weight is now 56,664, the gross weight is 536,774 kg,
1,180,903 lbs., and the sea level thrust of the 4 engines is 1,358,024
lbs.
*Using the average Isp of the NK-33 as the midpoint of the sea level
and vacuum Isp's at 315 s, the achieved delta-V would be 315*9.8*ln
(536,774/(56,664+180,110)) = 2,527 m/s, comparable to the equivalent
delta-V, speed + altitude, provided by the Ares I first stage. The
achieved delta-V is actually higher than this since the rocket spends
most of the time at high altitude, where the Isp is closer to the
vacuum value.
Note that if you want to increase the delta-V, the space occupied by
the crew compartment is now empty. This gives an additional 74 cubic
meters that could be used for propellant, which amounts to 74,000 kg
additional lox/kerosene propellant that could be carried.
Then we could still use the planned upper stage of the Ares I while
having a significantly lower development cost and per launch cost of
the now reusable first stage.


In addition to the Air Force wanting to build reusable first stages
with expendable upper stages to cut launch costs, the Europeans are
also planning such boosters, though sled launched:

Hopper (spacecraft).
http://en.wikipedia.org/wiki/Hopper_%28spacecraft%29

Europe's space shuttle passes early test.
* 16:05 10 May 2004 by Maggie McKee
"Europe took a step towards creating an unmanned space shuttle on
Saturday when a prototype landed autonomously after a test flight in
Sweden.
"The shuttle prototype, called Phoenix, is one of several proposals
for a European reusable launch vehicle (RLV) planned to cheaply ferry
satellites into orbit by 2015."
http://www.newscientist.com/article/dn4975

"An unmanned scale model prototype of the planned European shuttle is
pictured during its first free test flight at the North European
Aerospace Test Range in Kiruna, Sweden 1,230 kilometers (770 miles)
north of Stockholm, Saturday, May 8, 2004. (AP Photo/Peter Degerfeldt,
Blue Sky AB, DLR/EADS)."
http://i.space.com/images/h_phoenix_flight_02.jpg

Reusable space transport systems to reduce cost.
Bremen/Le Bourget, 01 June 2001
"In its HOPPER concept, Astrium has gone for an autonomous transport
system that is noted for its high degree of reusability and
comparatively low mission costs. Although the unmanned HOPPER is very
similar in appearance to the US Space Shuttle there are, however, some
substantial differences: The system will be launched horizontally on a
skid sled running on a four kilometre long track. The vehicle itself
is more compact than the Space Shuttle. The re-entry angle will be
optimised so as to keep the frictional heat at the outer skin
substantially lower than that of the Space Shuttle. This will allow
the sensitive and expensive thermal protection shield to be replaced
by an affordable, low-maintenance heat protection system. Due to these
features, Hopper is intended to transport payloads to orbit at 75%
lower cost than conventional transport systems."
http://www.eads.net/1024/fr/pressdb/...rium_reus.html

This article said the "Hopper" is more "compact" than the shuttle
orbiter, but actually it's about 13 meters longer with a 3 meter wider
wing span. This will allow it to have internal propellant tanks and
also an internal payload bay:

http://www.hobbyspace.com/AAdmin/Ima...RLVConf_md.jpg

The Europeans expect to use upgraded versions of Ariane's hydrogen-
fueled Vulcain engine. The choice of the hydrogen-fueled Vulcain,
rather then a kerosene engine typically used for first stages, perhaps
stems from the desire to have it be sled launched, requiring a lower
GLOW, and the desire to use the ESA's most advanced engine.
Rather than expending such large amounts of money building their own
Hopper vehicle, it might be cheaper as a technology demonstrator for
ESA to adapt the shuttle/Buran for the purpose. NASA seems to want to
give the SSME engines away for free, so the ESA could even get the
needed engines.
The shuttle/Buran is smaller than the proposed Hopper. To get similar
payload to orbit on an expendable upper stage, about 7,500 kg, they
could have it be vertically instead of sled launched to allow the
upper stage to be attached on the vehicle bottom. This would then
allow the full fuselage to be used for propellant.
However, as I have argued by using kerosene instead as the propellant
for this first stage you could have the expendable upper stage be as
heavy as that of the Ares I second stage at 180,000 kg, and with a
much larger payload to orbit than 7,500 kg, at about the size of the
Orion capsule, 20,000 kg to 25,000 kg.


Bob Clark