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The underside LAS
In my latest article, "How to design a lighter Orion", I've suggested to build a Truncated Biconic Shape Orion to save up to 2 mT on the capsule's mass (and much more on the SM, LAS and Ares-I mass) but the best way to save on the Orion mass and launch it with a smaller Ares-I, is to develop and build the (very much) simpler and lighter "underside Launch Abort System".
The planned Orion's LAS (fig.1) is a traditional "tower-LAS" design that looks (and is) very close to the Apollo LES (Launch Escape System) that is supposed "safe and reliable", despite (fortunately, of course) it has NEVER saved a manned capsule in a REAL launch abort. The main problem of the tower design is its weight (over 6.1 mT in the Orion's LAS) so, I suggest to adopt a new and simpler version of LAS.
My idea is to design a new LAS (fig.2) with four smaller solid motors joined with the thermal-shield's protection panel (that must have a set of explosive bolts between it and the Service Module) under the Orion that works like the second (vertical ejection) version of Shuttle's Crew Escape Module suggested in my article "The SAFE Space Shuttle".
If something goes wrong the "underside LAS" works like a standard tower-LAS but it's lighter and (I think) safer than the tower design.
If the Orion's flight goes fine an no problems will happen, the four solid motors will be simply detached (not jettisoned!) at the same altitude planned for the tower-LAS (around 70 km and a few seconds after the 2nd stage ignition) without any jettison motor but just activating the explosive bolts between the motors and the TPS protection panel.
The Nose Cone (with the integrated Attitude Control Motors) remains joined with the capsule until it reaches the first (elliptical) orbit, then it is (simply) deployed and will decay from its orbit like the 2nd stage, to burn in the atmosphere.
The adoption of this new design may result in an GIANT saving of (Orion and Ares-I) weight and money especially if used with the proposed TBS-Orion. Infact, with a lighter (8 mT) Orion the tower-LAS can weigh only 5 mT (instead of 6.1 mT for a standard 9.5 mT Orion) while, the underside LAS (without the Boost Protective Cover, Adapter Cone, Jettison Motor, Interstages, etc.), may weigh around 3.5 mT (you can see from fig.1 that the Abort Motor is only part of the entire mass and volume of a tower-LAS).
A further mass' reduction may come from a resizing of the four solid motor under the Orion, since, with (both) a smaller Orion AND a smaller LAS, the total mass the LAS must drag in a launch abort falls from the (Orion + LAS) 15.5 mT of the current design to less than 11.5 mT of the (TBS-Orion + underside LAS) new design, so, the final underside-LAS mass may fall to less than 3 mT (or HALF the weight of the standard Orion's tower-LAS).
The final mass of the full (TBS-Orion + underside-LAS + SM-light + propellent) vehicle will be less than 20 mT so, it can be launched with a simpler and cheaper Ares-I or with another (ready available) rocket like the Ariane5 or the Delta IV Heavy (that, however, must be man-rated to launch the Orion).
Looking at the two images published in this page (tower-LAS and underside-LAS) it's clear that the latter is also more aerodynamic than a tower-LAS (so the Orion may give less drag in the atmosphere and the Ares-I needs less power to lift it) but I think that my design is (also) safer than a tower-LAS.
As already said, a tower-LAS is "supposed" to be "safe and reliable" but that was NEVER evidenced so far in a REAL launch abort (or, maybe, once in a Soyuz launch) while, with an increased launch-rate, it may have some (possible) problems in some (extreme, but possible) contingency scenarios ...like:
1. the LAS is activated but, since it gives an high thrust in a fraction of second, the capsule-LAS explosive bolts don't resist that force, so, the Orion still remains joined to the rocket, while the LAS flies away.
2. the LAS works properly and the Orion is quickly moved away from a defective (or, maybe, exploding) rocket but, when it ends burning, the LAS isn't jettisoned and its Boost Protective Cover remains joined with the capsule, so, the Orion is still alive, but falls like a rock since it can't open its parachutes.
3. the Ares-I flight goes fine but, at 70 km of altitude (where the LAS must be jettisoned) it doesn't work and remains joined with the Orion, so (probably, but not sure) the astronauts can reach a stable circular orbit (with the Ares-I and SM engines) but can't continue the Moon mission nor come back to the Earth.
February 10 - 2007
In my first version of the "newLAS" (fig.2) I've missed a very interesting option to save a further ton of mass over the (very heavy) Orion's tower-LAS.
Since the standard tower-LAS has its own Nose Cone and the Attitude Control System I've merged them in a single module atop the Orion.
But the additional ACS is completely unnecessary for my LAS since an Orion will already have a FULL SET of powerful, accurate and reliable Attitude Controls Jets (fig.3) that (also) have 10+ times the fuel of a tower-LAS ACS since the Orion Jets must stabilize the capsule in the very complex and risky 15 minutes long Orion re-entry in the atmosphere at 25,000 mph, after a Moon mission!
The Orion's Jets can't be used as Attitude Control Motors in the Apollo-like Orion's tower-LAS, since its BIG Boost Protective Cover hides ALL engines nozzles while, in my LAS design (without any BPC) all Orion's attitude jets are free to work, also, the large amount of attitude jets' fuel (sufficient for whichever kind of launch abort operations) completely exclude the need of any Canard system!
The new (simpler and lighter) version of LAS (fig.4) has a very simple and light Carbon fiber Orion's Nose Cone that, thanks to its (~100 kg.) low weight can be carried in orbit, then (simply) detached, to decay from the elliptical orbit and burn in the atmosphere together with the Ares-I 2nd stage and interstage.
Thanks to the further mass' saving that comes from the use of the standard Orion's Attitude Controls Jets as LAS ACS, the four (small) Abort Motors can be further resized in (both) the standard-Orion and the TBS-Orion!
My evaluation is that a newLAS for the (9.5 mT) standard-Orion will have a total mass of only 2 mT while the newLAS for my (8 mT) TBS-Orion may have a total mass of only 1.7 mT with a GIANT (4+ mT) mass' saving over the standard-Orion's (very heavy) 6.1 mT tower-LAS !!!!!
February 18 - 2007
Latest (bad) news says that the current design's gross lift-off weight (GLOW) of the Orion+SM+LAS still is an overweighted 30,664 kg. while the target GLOW (to allow its launch with the expected Ares-I payload specs) is 28,934 kg., but the good news is that NASA plans to adopt a shrinked Service Module with an external diameter much lower than the 5 m. Orion and that choice simplifies very much the use of a (smaller, cheaper and lighter) underside LAS (fig.5) since it leaves free all sides around the Orion-TPS protection (to join the small solid motors of the newLAS).
The number of solid micromotors under the Orion can be increased to SIX (or more) to increase the Orion's stability in abort mode and to reduce the risks (VERY HIGH if the four-nozzles' SINGLE motor of the towerLAS explodes!) also, the motors can be arranged vertically for a good aerodynamic shape, and, if necessary, each micromotor can have a single-nozzle/single-direction (very small) attitude control jet.
The SM's protection fairing must be shaped to put these micromotors outside it, to protect the SM tanks/propellent, direct the motors' burn and work as slides to quickly detach them away from the rocket when they must be jettisoned.
As further option (useful but not easy to implement and use) the newLAS can be built with twelve+ (much smaller) micromotors so they can be used like a "third stage" to reach the orbit burning four-six motors a time, in two-three sequences (with the SM and the fairing still joined) to avoid a too high G for astronauts, then, when Orion will reach the elliptical orbit, the micromotors and the protection fairing will be (simply) detached, and a brief SM engine's burn performed, to circularize the Orion's orbit.
My evaluation is that this newLAS design may allow a GLOW reduction of about 3.5 mT (from the estimated 6.5 mT of the current towerLAS design) for the standard (cone-shaped) Orion (TWICE+ the NASA target with a fingers' snap!) and over 4.5 mT saved if used with a TBS-Orion that (also) needs a smaller SM and less propellent to be launched with a simpler, smaller and cheaper rocket!
April 5 - 2007
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Copyright © 2007 Gaetano Marano - All rights reserved - base images used for the drawings are © NASA