| Wednesday,
March 12, 2003
Subject: Hey Dr. P.
I'll bet you get a kick out of this:
http://www.deanesmay.com/archives/000946.html
-- Dean Esmay
You're right. Thanks.
Subject: Wonderful typo!
Check out http://www.theregister.co.uk/content/28/29687.html
, for an incredibly apt typo!
JoeZ
Indeed
Hi Jerry!
Did you see this Spacedaily article about Project
Orion?
http://www.spacedaily.com/news/nuclearspace-03h.html
Best regards,
Wayne.
It's quite good. Thanks.
Hello Mr. Pournelle,
I know that you are a strong advocate of hydrogen as
the new fuel. I found an article in Wired-magazine recently which might
interest you :
http://www.wired.com/wired/archive/11.04/hydrogen.html
Kind regards,
Rob Baartwijk The Netherlands.
It's not so much that I am a strong advocate of
the Hydrogen Economy as that it's an alternative to the war, and to
dependence on oil. The problem is there are no hydrogen wells. There are
natural gas wells, and there seems to be more and more natural gas. Given
electricity (from nuclear fission at first, from space solar power
platforms sustainably) we still need ways to distribute and use the
energy, particularly in mobile systems. Hydrogen is messy and tricky stuff
-- we have learned a lot about it since I wrote The Hydrogen Economy in
1976 -- but it is one way to distribute energy, and given fuel cells a way
to power mobile systems.
We need to work 0n distribution of energy and
also on non-fossil generation methods that are more under US control.
Fission is one source. Ground Solar is another. Over time Space Solar is
the cleanest and in some ways simplest once we get the cost to orbit
down.
From Richard, a summary of
X programs:
Flight International
August 06, 2002
SECTION: Features; Cover Story; Pg. 30
HEADLINE: X-planes advance; US industry is pushing
for government funding of more X-vehicle experimental programmes in a
drive to maintain its technological edge in aerospace
BYLINE: Graham Warwick/Washington DC
BODY: From the X-1 to the X-50, over a span of 56
years, the USA's famous series of experimental vehicles has contributed
uniquely, if not always successfully, to the advancement of aerospace.
The pace with which X-programmes are launched has
picked up in recent years, with an emphasis on demonstrating technology
for unmanned air vehicles and reusable launch vehicles.
US industry would like to see the pace increase
further, as flight demonstrators help to attract new talent, as well as to
develop the skills and retain the services of experienced engineers.
Despite a high mortality rate among modern X-vehicle
programmes -- for technical and budgetary reasons -- several are active,
and more are likely to emerge from programmes such as NASA's Space Launch
Initiative.
This review of currently and recently active
programmes illustrates that the USA's X-vehicle culture remains vibrant --
and the envy of other industries.
X-31 -- EXTREME VECTORING
Flight testing of the Boeing/EADS X-31 -- the first
international X-plane -- has resumed under the VECTOR programme to
demonstrate extremely short take-off and landing (ESTOL) capability.
Funded by the US Navy and the German defence ministry, the $53 million
programme involves the use of thrust vectoring and high angle-of-attack (AoA)
approaches to reduce landing speeds by up to 30%.
Two X-31s were built by Rockwell (now Boeing) and
MBB (now EADS) for the US/German Enhanced Fighter Manoeuvrability
programme, and completed 580 flights between October 1990 and June 1995,
demonstrating the tactical utility of post-stall manoeuvring using
three-axis thrust vectoring. Powered by a single General Electric F404 and
fitted with thrust-deflecting paddles, the canard/double-delta aircraft
was flown to post-stall AoAs up to 70deg. and outmanoeuvred Boeing F/A-18s
in simulated air combat. Later flights simulated tailless operation. The
No1 aircraft crashed in January 1995 at Edwards. The pilot ejected safely.
The follow-on VECTOR (Vectoring ESTOL Control
Tailless Operation Research) programme began in March 2000, the surviving
X-31 returning to flight status at Patuxent River in February 2001. The
aircraft was then modified with new flight control software, flush
air-data system, autothrottle, triplex air-data and
inertial-navigation/global-positioning systems, belly camera and
associated cockpit display, and high-integrity beacon landing system.
Flying resumed in May.
ESTOL testing is planned to begin by November,
involving approaches to a "virtual" runway at 5,000ft (1,525m)
altitude. Approaches will be flown at AoAs up to 35deg. with the gear up
and 25deg. with the gear down, to check out the GPS-based precision
landing system, which uses ground-based "pseudolites". A total
of 25 flights are planned. ESTOL "to the ground" testing is set
to begin in December, with 20 flights planned. Approaches will be flown
hands off at AoAs up to 25deg..
The X-31's normal approach angle of attack is
12deg., resulting in a landing speed of 160kt (295km/h). At an AoA of
25deg., landing speed will be reduced to around 115kt. The aircraft will
automatically pitch up to the required AoA, fly the approach and
"de-rotate" just before touchdown.
Plans for extremely short take-offs and
tailless/reduced-tail flights have been cut for budgetary reasons. EADS's
primary interest in the VECTOR programme is in demonstrating its advanced
air-data system. This promises to provide more accurate information,
particularly at high angle-of-attack and low speed. The low-observable
system has 12 flush pressure ports located radially around the X-31's
modified nose cone.
X-32 AND X-35 -- FIGHTER
FORERUNNERS
Boeing and Lockheed Martin were awarded Joint Strike
Fighter (JSF) concept demonstration contracts in 1996. Each built two
aircraft -- designated X-32 and X-35 -- to demonstrate commonality between
the three JSF variants, carrier approach handling qualities, and short
take-off and landing (STOVL) performance.
Boeing's X-32A was flown 66 times between September
2000 and February 2001 to demonstrate both the conventional take-off and
landing and aircraft carrier variants of Boeing's JSF design. The X-32B
STOVL demonstrator was flown between March and July 2001, completing 78
flights.
The delta-wing, twin-tail X-32 was powered by a
single Pratt & Whitney F119-614, with a direct-lift STOVL propulsion
system in the X-32B. In STOVL mode, the two-dimensional thrust-vectoring
cruise nozzle was closed, redirecting engine thrust to two swivelling lift
nozzles.
Lockheed Martin's X-35A completed 27 flights during
October and November 2000 to demonstrate the conventional take-off and
landing version of the company's JSF design. It was then converted to the
short take-off and landing variant, making 39 more flights as the STOVL
X-35B between June and August 2001. The carrier variant was represented by
the X-35C second demonstrator, which was flown 73 times between December
2000 and March 2001.
Resembling a scaled-down F-22, the X-35 was powered
by a Pratt & Whitney F119-611, with a shaft-driven lift fan mounted
behind the cockpit in the X-35B. In STOVL mode, the cruise nozzle was
swivelled downward, the lift fan engaged and engine bleed air ducted to
roll posts in the wing. In September 2001, Lockheed Martin was selected to
develop the F-35 JSF based on the X-35 demonstrator.
X-33 AND X-34 -- TERMINATED
TESTBEDS
Lockheed Martin signed a co-operative agreement with
NASA in 1999 to design, build and fly the X-33, a half-scale technology
demonstrator for its VentureStar single-stage-to-orbit reusable launch
vehicle. Suborbital tests were planned with the unmanned X-33, but
technical problems led to delays and cost overruns and in March 2001 the
programme was cancelled after NASA had spent more than $900 million and
industry over $350 million.
The lifting-body X-33 was designed to take off
vertically powered by a Boeing Rocketdyne XRS-2200 linear aerospike rocket
engine, then glide back to a horizontal runway landing -- all
autonomously. The programme came unstuck in November 1999 when the X-33's
composite liquid-hydrogen fuel tank failed during ground testing, delaying
a first flight from 2000 to 2003.
Like the X-33, Orbital Sciences' X-34 reusable
launch vehicle (RLV) technology demonstrator fell victim to cost overruns
and a change in direction at NASA. The programme was cancelled in 2001
after three of the unmanned air-launched testbeds had been built and three
captive-carry flights conducted under Orbital's Lockheed L-1011 TriStar
carrier aircraft.
Orbital was awarded a contract in 1996 to develop
the X-34 as a low-cost testbed for RLV technologies including
all-composite airframe and autonomous landing system, but costs had risen
to $205 million and powered flights slipped to 2002 when the programme was
cancelled.
In 2000, NASA launched its five-year, $4.8 billion
Space Launch Initiative (SLI) to develop technology for a
second-generation RLV to replace the Space Shuttle. But the agency decided
the benefits to be derived from flight testing the X-33 and X-34 did not
warrant the use of SLI funding to take the programmes to completion.
X-36 -- TURNING TAILLESS
Boeing (originally McDonnell Douglas) built two X-36
tailless agility research aircraft for NASA -- 28%-scale remotely piloted
models of a proposed low-observable fighter. The unmanned aircraft
completed 33 flights between May 1997 and December 1998. A canard
configuration with lambda wing, using spilt ailerons and thrust vectoring
for directional control, the X-36 demonstrated greater agility than
current generation fighters despite having no vertical or horizontal tail.
The last two flights were conducted for the US Air Force Research
Laboratory to demonstrate the ability of neural-net flight control
software to compensate for the damage or failure of control effectors on a
tailless fighter. X-36 hardware and software, avionics, flight controls
and Williams International F112 engine, have been reused for Boeing's X-50
canard rotor/wing demonstrator.
X-37 -- REUSABLE SPACEPLANE
Final assembly of the X-37 reusable spaceplane is
under way at Boeing Phantom Works under a $173 million cost-sharing
agreement with NASA signed in July 1999. Unpowered atmospheric drop tests
of the unmanned vehicle are scheduled for early 2004, from NASA's Boeing
B-52.
The original plan for orbital flight tests has been
shelved, but Boeing has proposed an on-orbit demonstration of the X-37
under NASA's Space Launch Initiative programme to develop technology for a
second-generation reusable launch vehicle. The company's SLI concepts
feature an X-37-derived upper stage.
The X-37 is designed to be carried into space on an
expendable launch vehicle, to operate on orbit for up to 21 days before
re-entering at up to Mach 25 and returning to a conventional runway
landing -- all autonomously. The vehicle has an all- composite airframe,
durable thermal-protection system, opening experiment bay and Boeing
Rocketdyne AR-2/3 on-orbit propulsion system.
The delta/twin-tail reusable spaceplane is scaled up
from the X-40A space manoeuvre vehicle, which was built by Boeing for the
US Air Force. Atmospheric drop tests of the unpowered X-40 have
demonstrated the autonomous runway acquisition and landing technology
planned for the X-37.
X-38 -- LIFEBOAT BEACHED
NASA has stopped work on the X-38, a prototype
emergency crew-rescue vehicle (CRV) for the International Space Station (ISS),
after new administrator Sean O'Keefe concluded the one-way mission was too
narrow. As a result, industry is working on designs for a more capable
vehicle able to carry crews to and from space.
The seven-occupant CRV was to be carried into orbit
by the Space Shuttle, and remain attached to the ISS until needed as a
lifeboat. The vehicle was then to glide back from orbit, jettisoning its
deorbit propulsion stage during re-entry and deploying a steerable
parafoil parachute for the final descent to a skid landing.
NASA, with involvement from the European Space
Agency, designed the X-38 in-house using the lifting-body configuration of
the US Air Force's Martin X-24A, flown in the mid-1960s. Two 80%-scale
atmospheric test vehicles were built by Scaled Composites and eight drop
tests from NASA's B-52 were conducted between March 1998 and December
2001.
On the final flight, the unmanned, unpowered X-38
was released at 45,000ft and flew autonomously, reaching transonic speed,
before being slowed by a drogue parachute and deploying the remotely
controlled steerable parachute. A third, orbital test, X-38 was nearing
completion when the axe fell. NASA plans to complete the vehicle for
instructional use.
X-39 -- FATE UNKNOWN
The designation X-39 is unassigned, but was reserved
for use by the US Air Force Research Laboratory and may have been intended
for subscale unmanned demonstrators planned under the Future Aircraft
Technology Enhancement (FATE) programme to evaluate technologies for
future fighters. Funding was transferred to the X-45 unmanned combat air
vehicle technology demonstrator.
X-40 -- DROPPING IN
Begun as a 90%-scale prototype of the US Air Force's
proposed Space Manoeuvre Vehicle (SMV), the unmanned X-40A has served as
an 80%-scale precursor for NASA's X-37 reusable spaceplane. The X-40,
which lacked the X-37's thermal protection and on-orbit propulsion, was
drop tested to demonstrate low-speed flight dynamics and autonomous
landing.
A single drop test was conducted under the SMV
programme in August 1998, from a Sikorsky UH-60 helicopter at Holloman
AFB, New Mexico. This was followed by seven drop tests at NASA Dryden,
from a Boeing CH-47 Chinook, in support of the X-37 programme. The X-40
was released at 15,000ft, autonomously acquired the runway and landed
conventionally.
X-41 AND X-42 -- IN THE BLACK
The classified X-41 is "an experimental
manoeuvrable re-entry vehicle carrying a variety of payloads through a
suborbital trajectory, then re-entering and dispersing the payload in the
atmosphere", says the US Air Force. Status is not known.
The X-41 is a technology demonstrator for the USAF's
proposed Common Aero Vehicle (CAV), a conventionally armed manoeuvrable
re-entry vehicle that could be deployed by a ballistic missile, aircraft
or spaceplane. Potential payloads include a 450kg (990lb) penetrator
warhead, four small-diameter bombs or six mini-missiles.
Also classified, the X-42 is "an experimental
expendable liquid rocket motor upper stage designed to boost 2,000-4,000lb
payloads into orbit", says the US Air Force. The status of this
programme to demonstrate technology for launch vehicle "pop-up"
upper stages is not known.
X-43 -- HYPERSONIC TRAILBLAZER
The X-43 is the centrepiece of revitalised US
research into hypersonics, with four versions planned. The X-43A is the
first in NASA's Hyper-X series of unmanned hypersonic flight
demonstrators.
The first flight in June 2001 ended prematurely when
the air-launched X-43A's Pegasus booster went out of control. A second
attempt at a Mach 7 flight is planned for May or June 2003. If successful,
the X-43 will become of the world's fastest aircraft, breaking the record
held for over 30 years by the rocket-powered X-15.
NASA's Hyper-X hypersonic experimental vehicle
effort is the scaled-back successor to the National Aero-Space Plane (NASP)
programme, which was cancelled in 1994. The X-43 is a small-scale model of
the X-30 piloted single-stage-to-orbit demonstrator planned under the
overambitious NASP programme.
The X-43A is intended to demonstrate an
airframe-integrated supersonic-combustion ramjet (scramjet) at M7 and M10.
Working with Boeing, MicroCraft has built three of the 3.7m-long
expendable vehicles, which are powered by an uncooled, hydrogen-fuelled,
dual-mode ramjet/ scramjet produced by GASL.
The vehicle is attached to a modified Orbital
Sciences Pegasus booster and air-launched from NASA's B-52. The Pegasus
boosts the X-43A to the test speed and altitude, where the vehicle
separates to fly autonomously and the scramjet ignites to burn for 5-7s.
The X-43A then descends to its destruction in the Pacific.
The failed first flight was planned to demonstrate
scramjet operation at M7, the highest speed possible in ground test
facilities. The second test will be a repeat attempt at a M7 flight, while
a third flight at M10 is planned for 2004. An M10 flight would provide the
first data with which to benchmark hypersonic computational fluid-dynamics
models.
The next version will be the X-43C. Scheduled to fly
in 2008, this vehicle will be powered by the HyTech hydrocarbon-fuelled
dual-mode scramjet under development by Pratt & Whitney for the US Air
Force. The fuel-cooled, flight-weight HyTech engine is expected to
accelerate the 4.9m long X-43C from M5 to M7 after separation from the
air-launched Pegasus. Ground testing of the engine began at GASL in July.
There are two powerplant options for the planned but
unfunded X-43B, a scaled-up version of the X-43A intended to demonstrate a
reusable combined-cycle propulsion system for future air-breathing launch
vehicles. NASA is developing both rocket-based and turbine-based engine
options for the X-43B, which is planned to fly in 2010.
The rocket-based combined cycle (RBCC) engine is
being developed by RBC3 -- a consortium of Aerojet, Boeing Rocketdyne and
Pratt & Whitney -- under NASA's Integrated Systems Test of an
Airbreathing Rocket (ISTAR) programme. The RBCC is capable of powering the
X-43B from zero airspeed to M8.
The turbine-based combined cycle (TBCC) powerplant
option is being pursued under NASA's Revolutionary Turbine Accelerator (RTA)
programme. The high-Mach turbine engine could power the X-43B from zero
airspeed to M4-5, where the HyTech dual-mode scramjet would take over and
accelerate the vehicle to M8.
General Electric has been awarded a contract to
build the ground-test RTA (Flight International, 30 July-5 August).
Rolls-Royce and Williams are competing to build the smaller flight-test
engine, four of which would power the X-43B, sharing inlets and nozzles
with the scramjets.
NASA plans to choose between the ISTAR RBCC and RTA
TBCC options after ground tests of both engines in 2006-07. The X-43B will
be released from the B-52 at M0.8 to power itself to M7 before gliding
back to a runway landing. The reusable vehicle will have a 25-flight
design life.
A potential follow-on vehicle, the X-43D, is being
studied by NASA. A direct development of the X-34A, this would be powered
by a cooled hydrogen-fuelled dual-mode scramjet, which would run for 10s
and accelerate the vehicle to M15.
X-44 -- DIRECTION REQUIRED
The designation X-44 MANTA (Multi-Axis No-Tail
Aircraft) is attached to a NASA/USAF proposal, currently dormant, to
modify a Lockheed Martin/Boeing F-22 prototype to demonstrate flight
without any aerodynamic controls, using multi-axis thrust vectoring. The
horizontal and vertical tails would be removed and a delta wing fitted.
Pitch/yaw-vectoring nozzles would provide all flight control.
A feasibility study has been conducted. The X-44, if
it proceeds, would be a follow-on to the thrust-vectoring X-31 and
tailless X-36, as well as the USAF/NASA ACTIVE (Advanced Control
Technology for Integrated Vehicles) programme involving a Boeing F-15
modified with multi-axis thrust vectoring.
Lockheed Martin has proposed the FB-22, a derivative
of the F-22 with delta wing and multi-axis thrust vectoring, to the US Air
Force as a long-range strike aircraft.
X-45 -- UNMANNED BOMBER
Flight testing of the X-45 unmanned combat air
vehicle (UCAV) began in May at NASA Dryden. Boeing Phantom Works has built
two X-45A technology demonstrators for the joint US Defense Advanced
Research Projects Agency (DARPA) and US Air Force programme, and is
designing a larger X-45B "fieldable prototype" UCAV.
The DARPA/USAF programme aims to demonstrate the
technical feasibility and military utility of using unmanned air vehicles
to perform suppression of enemy air defences (SEAD) and strike missions
autonomously. Testing of the two X-45As will culminate in 2004 with an
end-to-end demonstration involving multi-vehicle control, co-ordinated
flight, inter-vehicle communications, dynamic retasking, co-operative
targeting and weapon release.
The 8m long, 10.3m span tailless X-45A has a 3,600kg
empty weight and is powered by a Honeywell F124 with yaw thrust vectoring.
The X-45B, more representative of the planned A-45 operational UCAV, is
9.8m long, with a 14.3m span and 6,350kg empty weight. The larger vehicle
is powered by a General Electric F404.
The X-45B has fully integrated avionics, two
functional weapon bays, low-observable features and provisions for the
full sensor suite, satellite communications and aerial refuelling. Three
vehicles are planned, with the first scheduled to fly in late 2004. They
will be used for increasingly complex multivehicle demonstrations
culminating in joint operations with manned aircraft as part of a strike
force.
X-46 -- CARRIER CAPABLE
The designation X-46A has been assigned to Boeing's
design for a naval unmanned combat air vehicle (UCAV-N). The US Navy and
Defense Advanced Research Projects Agency plan to award at least one
contract to demonstrate an unmanned vehicle able to operate from aircraft
carriers and perform surveillance, suppression of enemy air defences and
deep strike missions.
Both Boeing and Northrop Grumman (see X-47) are
working under UCAV-N risk-reduction contracts awarded in May. Boeing's
proposal draws heavily on its X-45 UCAV for the US Air Force. The
tailless, flying-wing vehicle would be roughly 10.4m long, with a 13.4m
span, and be able to carry 1,200kg of munitions up to 1,200km or perform
surveillance missions lasting up to 12h.
X-47 - UCAV ON DECK
Northrop Grumman has built the X-47A Pegasus as a
private venture to support the design of a naval unmanned combat air
vehicle. The kite-shaped experimental unmanned vehicle is being prepared
for flight testing at China Lake, California, and is intended to
demonstrate aero-dynamic qualities suitable for autonomous operations from
an aircraft carrier.
The tailless X-47A is 8.5m long, with a wing span of
just under 8.5m, and is powered by a Pratt & Whitney Canada JT15D
turbofan. A total of 15h of flight testing is planned, involving up to 40
landings. The vehicle is a precursor to the larger X-47B UCAV-N technology
demonstrator.
Northrop Grumman was awarded a UCAV-N risk-reduction
contract in May, as was Boeing, and is awaiting release of a request for
proposals to build the full-scale demonstrator. This has been delayed
while DARPA and the US Navy debate whether to award one contract or two,
to maintain competition for the UCAV-N development programme scheduled to
begin in 2007.
X-50 - HALF AND HALF
Boeing plans to begin flight testing its X-50A
Dragonfly Canard/Rotor Wing (CRW) technology demonstrator in September at
Yuma, Arizona. CRW is a vertical take-off and landing concept that aims to
combine the hover efficiency of a helicopter with the cruise speed of a
fixed-wing aircraft.
The manufacturer and US Defense Advanced Research
Projects Agency are sharing the $21 million cost of the CRW demonstration
equally. Boeing Phantom Works has built two subscale, unmanned X-50As
reusing avionics, flight controls and Williams F112 engines from the X-36
tailless fighter demonstrators.
CRW differs from previous stopped-rotor designs in
that lift during conversion between rotary- and fixed-wing flight is
provided by a forward canard and aft horizontal stabiliser. This allows
the rotor to be unloaded, slowed, stopped and locked perpendicular to the
fuselage. In helicopter mode, exhaust from the turbofan engine is ducted
to tipjets on the two-blade reaction-drive rotor. During conversion to
fixed-wing mode, engine exhaust is diverted progressively away from the
rotor/wing to an aft cruise nozzle.
An operational manned or unmanned CRW is expected to
be capable of cruise speeds up to 375kt and altitudes approaching
35,000ft. The X-50A is not designed to go beyond 150kt as testing will
focus on conversion between rotary- and fixed-wing mode. Eleven flights
are planned. The X-50A will take off vertically and operate as a
helicopter at speeds up to 60kt. Above 60kt, the canard and stabiliser
will begin to generate lift and by 120kt will support the vehicle's
weight. Conversion to fixed-wing flight will take place at 130kt.
The CRW is a candidate configuration for the DARPA/US
Army Unmanned Combat Armed Rotorcraft programme, which is likely to result
in the next in the illustrious series X-vehicle series.
A good summary of what's going on.
On education
Jerry,
http://www.washingtonpost.com/wp-dyn/
articles/A10275-2003Mar11.html
I know you are concerned about our school systems.
It is nice to read something nice about them once in a while. While they
are often criticized, an by no means perfect, our schools are providing
the graduates to keep our technical edge, and there are many that wish to
study here.
doug mccaw
I become increasingly less optimistic about the
public school system. Sometimes there is good news, but usually there is
not. The purpose of a bureaucracy is to hire and pay bureaucrats. The
Soviet system of agriculture could not be fixed. NASA can't be fixed. The
US Education system is organized like the above two institutions.
On Single Stage to Orbit
Dr. Pournelle
In your reply to my email you mentioned several
things. These are:
· SSTO-TSTO & economics · Military SSTO ·
Wings-going up and coming down.
I will put in my 2 cents worth on these subjects in
order. My time in product development introduced me to several concepts.
Nonrecurring costs, recurring costs, and internal rate of return.
Obviously, an SSTO has a smaller recurring (operational) cost. It also has
a higher nonrecurring cost (development). How does one choose? That goes
back to the market. If one can 12 launches a year, then even an
outstanding reduction in operational costs doesn't justify the initial
development expenditure. If one sees a thousand launches a year, then even
a modest reduction in operations justifies the initial development. Right
now anyone talking about reusable systems projects something called
"market elasticity." Essentially build it and they will come. If
the price comes down, payloads will materialize that didn't exist before.
I believe that. But it takes more than belief when one is talking about
investing hundreds of billions of dollars. One of your writers referred to
risk. There is lots of risk involved and the success usually doesn't work
its way to those making the decisions. I once joked that I'd like to be a
vice-president. I could sit in a corner office and say "No, no,
no," all day long just as well as anybody else and I could sure use
the cushy salary. So, I favor TSTO as the next step. The initial
development costs (and risks) are reduced. Sure, we pay the operations
costs, but that comes in the future. Meanwhile we drive down launch costs
and expand the market. Then, by the time the TSTO design is showing its
age (say ten years), the information on market and operations costs
encourage a move to the SSTO. One has to crawl before one can walk or run.
I am sorry about the cliché.
Now I will turn to military SSTOs. Certainly, our
blue suited friends would prefer the operational ease of a "strap in
on and go anytime vehicle." But now are we stretching things even
further. I would surmise that the military mission would be to dominant
the Earth through space assets. And this would mean overflying the Earth's
entire surface, which tells us that a military craft must be capable of
Polar orbits. This changes our vehicle's delta V ground rules from 30000
fps to 31500 fps. Now let us compare vehicles:
Straight East-low inclination Payload Glow empty wt
diameter dev cost 6,000 602,206 65,942 16.53 $396,000,000
Polar Payload Glow empty wt diameter dev cost 6,000
798,000 78,900 19.05 $474,000,000
2 Stage Polar Payload Glow empty wt diameter dev
cost 6,000 275,850 40,157 11.2 $241,000,000
The military may be forced to prefer TSTO or SSTO at
least for the first generation of resuables.
Now I turn to Wings. Wings are pretty useless in the
vertical phase. Most winged vehicles are sized for re-entry. On ascent,
the craft masses much more and the lift is not worth the drag. One a two
stage vehicle, one could play games with lift, drag, and mass. I agree the
advantage to wings is on re-entry and not for the "airplane like
landing." Wings produce decent lift and that works out to cross-range
on re-entry. A vehicle in orbit occupies a plane orbiting the planet.
Earth spins beneath that plane. If we wish to return to a certain point on
the Earth's surface, like KSC, we must initiate re-entry when the Earth
spins through the orbital plane. If our vehicle is not in the right
position with regard to KSC, we may land uprange or downrange of our
intended landing site. Notice, the Soyuz craft doesn't have specific place
to land but an area. Therefore, exact phasing (raising or lowering its
orbit) needs to be done to position it correctly for re-entry. But with a
winged vehicle, it can fly left or right of its orbital plane to allow it
to maneuver to a landing position at a point on the Earth's surface. When
one observes orbital operations. A re-entry can be "waved off"
for one rev if the weather isn't perfect. This wouldn't happen with a
minimal cross-range craft; a "wave off" could be for 12 or 24
hours. This complicates vehicle design. Also, a reusable vehicle is less
viable if its spending its time waiting on orbit instead of doing what's
supposed to do, namely lifting stuff up. One does not need wings to get
cross-range. A biconic gives somewhat good hypersonic L/D. All these
things need to be taken into account.
These are my observations
(name withheld)
And really the point is that we can argue
forever; but until we FLY some x projects that incorporate some of the
technologies and get some data, we will continue to argue. The DC/X
demonstrated that a major X project can be built on time and in budget to
produce flying hardware that can be operated by a small operations crew,
as well as that you can control a pure rocket at low speeds and altitudes,
and that the flight crew need not only not be aboard, but the whole flight
crew can be 5 people, not the thousands needed by Shuttle.
But of course it was single stage to a few
hundred feet. Never mind, until it flew there were many experts who knew
even that couldn't be done.
Build more experimental ships. Or as we said in
the 1986 report of the Citizens Advisory Committee on National Space
Policy, AMERICA A SPACE FARING NATION : "Build more rocket ships. Fly
more rocket ships."
MORE ON EDUCATION
Dr. Pournelle:
CBS 60 Minutes for Sunday, March 9, had a segment
dealing with IIT--Nehru's Indian Institute of Technology. The entrance
requirements are very stiff, the courses tough, and the students
well-prepared for virtually any technical job.
One student, who managed to pass the entrance exam,
but who was not within the top 200 (these students pick their major, the
others are assigned one) decided to go to his second-choice school, on a
full scholarship. The college he attended was Cornell.
Frightening.
Mark Thompson jomath@mctcnet.net
A sobering thought indeed. Our higher education
system used to be all right but it's being affected by having to do high
school in college.
Abolish the public schools. What we get instead
can't be worse than this. Or can it?
TOP
CURRENT
VIEW
|
CLICK HERE for
a Special Request. 
