Thursday, September 13, 2012
Wednesday, September 12, 2012
Some of the early design issues with reusable vehicles
Some of the early design issues
with reusable vehicles, and that shown to be enormous challenges, were
stability, control, aerodynamic heating and hypersonic flow fields [1]. X-1A
and X-1B proved inadequate stability at Mach 2.44. At this speed, the aircraft
diverged and spun to almost the impossibility of landing safely. X-2 experienced
inadequacy of aerodynamic control at 126,200 feet altitude and a speed of Mach
3. The aircraft diverged out of control and it could not be recovered [2].
These control difficulties experienced by the early X-planes later led to
thruster reaction pitch, yaw and roll, while aerodynamic heating issues led to
the development of new alloys to stand up to high temperatures during the high
speed flights [3] With the stability issues encountered by X-1 and X-2 at lower
Mach speeds than expected, NACA suggested the replacement of the supersonic
airfoil with a wedge shaped vertical tail. This kind of tail would give a
higher maneuverability to control the vehicle if it diverged, as well as
directional stability [4]. Such design changes (thruster reaction and wedge shape
tail) would be implemented in the X-15 in order to achieve a speed of over Mach
3. To deal with the heat, designers chose a hot structure and the plane was
meant to fly at the maximum heat tolerance of the alloys, which was expected to
be around Mach 7. Although X-15 was designed to fly “fast and hot - the faster,
the hotter, the better” [5], and not necessarily high, the X-15 managed to
reach above the atmosphere. It was then noticed that over 200,000 feet altitude
there was no more any kind of aerodynamic reaction control [6]. Despite the
fact that human space flight was not yet considered at that time, another
important issue discussed was reentry, both in regard to heating and stability.
Notes:
[1] Armstrong, Neil A. The X-15. Next Generation
Suborbital Research Conference (NSRC), 2012. YouTube (accessed September 9,
2012).
[2] Ibid.
[3] Jenkins, Dennis R. Space
Shuttle - The History of the National Space Transportation System. World
Print Ltd, Hong Kong , 2010, 5.
[4] Ibid, 6.
[5] Armstrong, Neil A. The X-15. Next Generation
Suborbital Research Conference (NSRC), 2012. (accessed September 9, 2012).
[6] Jenkins, Dennis R. Space
Shuttle - The History of the National Space Transportation System. World
Print Ltd, Hong Kong , 2010, 5.
References
Armstrong, Neil A. The X-15. Next Generation
Suborbital Research Conference (NSRC), 2012.
Jenkins, Dennis R. Space Shuttle - The History of the
National Space Transportation System. World Print Ltd, Hong
Kong , 2010.
Monday, September 10, 2012
Vision for Space Exploration
Humans need to
learn deep space travel, as well as living in space. There is no way around
this if the species is to survive. Although such endeavors may still seem to be
science-fiction, the ultimate scope of all these endeavors is the survival of
the species by means of colonizing other celestial bodies. Exploring the Moon
and Mars are definitely the correct destinations, and explain the reasons
behind Visions of Space
Exploration.
Visions of
Space Exploration came in a moment of stagnation in the U.S. space program, with the goal to advance the
scientific, security, and economic interests of the United States
The main event
that caused this aggressive and audacious change in the U.S. space policy was the Columbia
Let us all
remember the Sixties, and the impact that the short presidential deadline for
landing a man on the moon and returning him safe to Earth had on the U.S. space
program. Such pushes have proved to be very fruitful, and this is why the
aggressive change intended by Visions
of Space Exploration was
necessary in times of stagnation. Crisis was overwhelming NASA in 2004. Having
to deal with the aftermath of the Shuttle Columbia’s accident, with the only
means to reach LEO grounded for unlimited time, unfinished business left in
orbit with no means to reach it, and no plans for the future, the entire space
program was in free fall. It seems to me that by proposing Visions of Space Exploration,
the President hoped for a reinvigoration of the space program, and tried to
re-bring the spirit of the Apollo program upfront.
Notes:
[1] NASA. 2004. The Vision for Space Exploration,
5.
[2] Ibid.
[3] Launius,
Roger, D. Frontiers of Space
Exploration. Westport : Greenwood
References
Launius, Roger,
D. Frontiers of Space
Exploration. Westport : Greenwood
NASA. 2004. The Vision for Space Exploration.
https://edge.apus.edu/access/content/group/178054/Readings/NASAVisionforSpaceExploration.pdf
(accessed April 5, 2012).
Tuesday, September 4, 2012
Launch Vehicles
The
Reusable Launch Vehicle (RLV) program was established in 1994 with the
objective to lower the costs for payload deliveries, and contribute to the
commercial launch systems. [1] X-33, developed by Lockheed Martin, and X-34,
developed by Orbital Sciences Corporation were part of this initial program. However,
they failed to meet both the financial and performance expectations. At that
time, the program’s goal was to reduce the payload costs. The cost of a pound
of payload on the STS was $10,000, and the new RLV’s were supposed to be able
to carry a payload at $1000 per pound. [2] The RLV’s feature of caring out more
missions is the low cost aspect of the program, since the same vehicle can
perform multiple trips to the LEO and back to Earth. However, a vehicle capable
to return to Earth and perform multiple missions is of course more expensive to
build. RLVs can feature: full reusability of one stage and partial reusability
of another stage (X-33, X-34), full reusability of one stage and expendable
other stages (X-38), and partial reusability of one stage. [3] The Space
Shuttle has been the most distinguished RLV. Its design phase began in the Sixties
and it successfully operated for about thirty years. [4] Recently SpaceX has
announced the attempt to produce a new RLV. SpaceX’s
RLV will display a first burning stage that will detach and return to Earth by
restarting the engines and landing vertically on the launch pad, as well as a
second stage that will deliver the payload, and then return for a vertical
landing. [5]
Expendable launch vehicles such as Lockheed Martin‘s Atlas, Boeing’s Delta IV, or Proton have no reusable
components. The Evolved Expendable Launch
Vehicles (EELV) program was also designed to make space launch more affordable
and reliable. [6] Delta IV is
the most advanced rocket developed by Boeing, with capabilities to transport one or more
payloads weighting from 9,480 to 28,620 lbs to GTOs, and over 50,000 lbs to LEOs, and can also launch
to polar, sun-synchronous orbits, geosynchronous and geosynchronous orbits.
The cost of one Delta IV launch is between $140 million and
$170 million.
[7] Falcon 9
is also a low cost expendable launch vehicle designed by SpaceX, and a much
more cost-effective one. The $1.6 billion contract between NASA and SpaceX
covers a minimum of 12 flights to the ISS. [8] The launch vehicles developed by
SpaceX seem to have increased reliability and performance, and reduced cost by
a factor of ten. Falcon 9 is estimated
to cost between 54 and 59.5 million dollars per flight. [9]
The U.S. space program should probably use the EELVs during
this decade, mainly because they seem more reliable, and although the RLV’s may
be lower cost in the long run, for the time being using the EELVs would be more
cost-effective. An excellent RLV with an outstanding performance and profitable
financially is yet to be designed, and while engineers and designers work on
this, it is best to rely on expendable launch vehicles
Notes:
[1] NASA. Reusable LaunchVehicle. http://www.sti.nasa.gov/tto/spinoff1996/14.html
(accessed March 29, 2012), para. 1
[2] GlobalSecurity.org. Reusable Launch Vehicle Program.
http://www.globalsecurity.org/space/systems/rlv.htm (accessed March 28, 2012),
para. 5-6.
[3] Federal Aviation
Administration. REUSABLE LAUNCH VEHICLE
PROGRAMS AND CONCEPTS. http://www.faa.gov/library/reports/commercial_space/dev_concepts/media/98rlv.pdf
(accessed March 28, 2012), 1.
[4] Ibid, 6.
[5] Rosenberg, Zach. SpaceX to build reusable launch vehicle.
FlightGlobal. http://www.flightglobal.com/news/articles/spacex-to-build-reusable-launch-vehicle-362729/
(accessed March 28, 2012), para. 2.
[6] Air Force Space Command. EVOLVED EXPENDABLE LAUNCH VEHICLE.
http://www.afspc.af.mil/library/factsheets/factsheet.asp?id=3643 (accessed
March 28, 2012), para. 1.
[7] Boeing. Delta IV Overview.
http://www.boeing.com/defense-space/space/delta/delta4/delta4.htm (accessed March 28,
2012).
[8] SpaceX, Falcon 9 Overview, 2011.
http://www.spacex.com/falcon9.php#falcon9_overview (accessed March 28, 2012).
[9] ORBCOMM, I. c., ORBCOMM and SpaceX Set Plans to Launch Satellites
on Next Falcon 9 Launch. Business Wire. EBSCOhost (accessed March 28, 2012).
Air Force Space
Command. EVOLVED EXPENDABLE LAUNCH VEHICLE. http://www.afspc.af.mil/library/factsheets/factsheet.asp?id=3643
(accessed March 28, 2012).
Boeing. Delta IV
Overview. http://www.boeing.com/defense-space/space/delta/delta4/delta4.htm
(accessed March 28, 2012).
Federal Aviation
Administration. REUSABLE LAUNCH VEHICLE
PROGRAMS AND CONCEPTS.
http://www.faa.gov/library/reports/commercial_space/dev_concepts/media/98rlv.pdf
(accessed March 28, 2012).
GlobalSecurity.org.
Reusable Launch Vehicle Program.
http://www.globalsecurity.org/space/systems/rlv.htm (accessed March 28, 2012).
NASA. Reusable Launch Vehicle.
http://www.sti.nasa.gov/tto/spinoff1996/14.html (accessed March 29, 2012).
ORBCOMM, I. c., ORBCOMM and SpaceX Set Plans to Launch Satellites
on Next Falcon 9 Launch. Business Wire. EBSCOhost (accessed
March 28, 2012).
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