Pinson - Mar 24, 2003
In a recent "Opinion Space" article, one bright man asked the (valid) question "Is The Shuttle Fatally Flawed?" The answer can only be: yes (with an asterisk *). The author of the above described column, Josef Pinkas, questioned the lateral position of the orbiter. I must take issue with him there, even if his is a popular position after the loss of both Challenger & Columbia.
He himself admits that Buran lost no tiles and there could be no problem with O-rings since the engine-equipped External Tank-become-carrier-rocket (the Energia) used safer kerosene-filled strap-on boosters of the kind he advocates. There were no foam problems, either.
What the author fails to understand is that top-mounted spaceplanes--even small ones--inflict tremendous pitch-loads and bending moments upon the vehicles they ride upon.
Having large limber shrouds surround them can only complicate escape options and further erode the already limited capabilities of small winged Orbital Space Plane (OSP) designs, whose avionics systems, life-support systems, landing-gear, docking ports, etc. all make up a much, much larger percentage of the overall mass of any such limited vehicle.
A Buran-type shuttle replacement for America, on the other hand, would have a better chance of using proven, off-the-shelf components, and would cause less pitch-loads or bending moments upon an Energia-type engine-equipped External Tank.
An Energia-Buran style side mount shuttle-replacement design might not please the anal mass-efficiency or aerodynamics purists, but it eliminates complications that arise from shrouds/fairings, reduces the overall height of the vehicle stack and allows outsized cargos like aerobrake disks or hypersonic testbed craft to be exchanged with Buran-style orbiters, since they are 'parasites-flyers' that could be swapped out with 100 ton payload pods like POLYUS, allowing for simpler space assembly of large objects like the International Space Station (ISS).
A side-mount Buran-like orbiter can have a longer nose and wider wingspans since pitch-loads are reduced with the vehicle stack being shorter. A Delta IV OSP stack would in fact be taller than was Energia/Buran, with a similar price tag at $13 billion or more.
Top-mount spaceplanes will have much more trouble than capsules separating from EELVs during an emergency on ascent, for they will encounter terrific aerodynamic loads trying to flip or push the vehicle right back down upon the very booster it is trying to escape froom--a booster which itself could surge and rush up to meet it, being lightened.
Any shrouds encircling an OSP can only complicate this escape process--unless the OSP winds up being a capsule--a step backward to the John Glenn days we cannot afford to take.
The External Tank of Challenger only failed due to the SRBs which have been redesigned. Future pressure-fed liquid fuel designs will be as simple to recover by parachute, eliminating risky fly-back contraptions. Had Challenger been more like Buran, but with an F-111 type cockpit-capsule, they would have survived, since the initial explosion was not the cause of death.
Many have called for future shuttle stacks to fly in a 'heads-up' attitude where the orbiter is in fact above its side-mount Energia-type booster. This configuration is not unlike TSTO designs like MAKS.
A side-mount orbiter in a 'heads-up attitude can supply lift. In-line OSP designs cannot do this, and will be obscured behind flaring EELVs which, having only ONE engine per core (CCB) has no engine-out capability that could be had by mounting three of Boeing's fine RS-68s underneath on External Tank. A Buran orbiter riding this powered-ET in a heads-up attitude! will be able to have an unobscured antenna in its tailfin.
If an accident occurs on a pad with a faulty escape system, the side mount F-111 type cabin will still be thrown clear from a flaming pad, where a top-mounted capsule with a malfunctioning escape system can only telescope straight down into a firestorm, with the crew breaking their backs on the way down if they pop up just a bit at first, only to fall straight down into an inferno.
Side mount designs allow for greater modularity. The Energia could be ringed with its Zenit first stage kerosene strap-ons, an upper stage added, and 200 tons could be taken to LEO in the Energia VULKAN iteration. The strap-ons were used as launch vehicles in their own right. Boeings' SEA LAUNCH venture uses ZENITS and the ATLAS V uses the Zenit-derived RD-180.
With parallel staging and a side payload mount, all engines are on ground level for ease of inspection unlike the over-complicated SATURN V, which had one dead-weight-on-lift-off stage perched atop another, perched atop another--with the bottom stage having to do all the work on lift-off.
The upper stages--with explosive bolts nearer their engines, had to both separate and ignite in the stratosphere during flight, and they could not be test-fired as part of the integrated vehicle stack without blowing it apart.
Due to massive vertical integration, none of the Saturn's stages could be used as cheap com-sat launchers like the much more modular Zenit strap-ons, which allowed all of the Energia Launch vehicle stacks engines to burn without obstruction. This also allowed the tops of all stages to be rounded off simply without the complex interfaces between stages.
Side-mounting also allowed for horizontal integration which eased worker fatigue a! nd made for faster, simpler payload-processing. This allowed for Energia to be rolled out, stood up and fueled without having to first build a skyscraper.
The engine-equipped External Tank that was the Energia used liquid hydrogen, keeping it in one tank (unlike Delta IV) which allowed for engine-out capability. Hydrogen is the cleanest fuel we know, has the highest Isp available, and is very light.
Its high-volume may require the use of a large tank, but this is no loss since there have been plans to use the evacuated tankage for 'wet-stage' modules for shuttle-derived Mars-ships/cyclers and space-stations (see Space Island Group for more).
The shuttle/External Tank combo as it is today is in effect, like the early Atlas, a Single-Stage (and a half) to orbit vehicle with less parts than a Saturn. The orbiter could take the External Tank to a higher orbit. Some have called for the Atlas cores to be used as Convair stations, and External Tanks can be used for even larger habitats.
A stretched External Tank can be a simple tanker since unused hydrogen can be its cargo, or if its burned with its engines, an outsized emptied External Tank can be placed in a libration point.
Even if none of these tank-salvage missions are done, engine equipped External Tanks like the Energia were able to place Mir-sized stations in geosynch. or 100 ton space-station modules in Low-Earth-Orbit (LEO) in just one launch in place of the 80 ton Burans with their 20 ton + internal cargoes.
These orbiters would service and outfit these 100 ton station nodes more simply. With only five launches of 100 ton pods, ISS would have been finished by now.
So not only does hydrogen allow for wet-stage construction (similar to the initial Skylab design), but Energia's hydrogen engines, the RD-0120s had less trouble in their development that did the early Zenit strap-on engines, the RD-170.
I understand Josef Pinkas' concern about anti-German, anti-European sentiment in America. Indeed Germans played a larger role in early Russian rocketry programs from Tsander on to Gotterup. But I am also concerned about those against cleaner hydrogen engines like the SSME, the RD-0120, or the Delta IV RS-68, with 90% fewer parts than the SSME.
But these hydrogen engines must NOT be located in the orbiter, as was the case with Columbia and her sisters because of the tremendous stress-loadinf upon the orbiter that must camber up to space loaded down with the hydrogen-filled External Tank that must be fed from through holes or pass-thrus in the orbiters heat shield.
Mr. Pinkas and I are in total agreement on that point. We should cut the umbilical on the shuttle orbiter--literally--so that it can grow up and be the modular launcher Energia-Buran was. By placing big hydrogen engines (SSME RD-0120, RS-68) underneath the External Tank--turning it into its own launcher, a simpler Buran-style orbiter of safer, simpler, cheaper construction that can be exchanged with other types of orbiters, 100 ton cargo pods like Energia's GTK, etc. becomes available--giving astronauts greater stability and more options.
Buran had no pass-throughs or foam problems, and was able to land in 20 knot ! cross-winds without the loss of a single tile--while automated, that is UNMANNED. A launcher need not be a skyscraper (to please the anal aerodynamicists) to be useful.
Hydrogen engines feed from the External Tank (ET) to start with, so it makes for simpler construction to put them on the ET anyway. This gives us an Energia-type booster that could take Buran-sized large scale hypersonic test vehicles that a first released from the back of the 747 orbiter ferry for low-speed tests, and then side launched and released from the powered-ET for re-entry and scram-jet tests.
By separating in the vacuum of space, the large scale boilerplate has a better chance than the tiny X-43. Thus the powered ET becomes a rocket version of the B-52, allowing future vehicles to be tested in large scale.
Let us abandon neither our European friends or those who have spent their lives promoting environmentally clean hydrogen engines. We can use the also clean RP for strap-ons (be they pressure fed Beal designs, the RD-171 or F-1) for the time being, so that our German friends or Russian friends and their achievements are not forgotten either. Therefore, I call for an 'Americanized Energia/Buran" shuttle-replacement that can use the latest technology from all the world.
Let us quit our sibling rivalries as heavy-lift enthusiasts and grow up.
It is time to cut the umbilical.
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Is The Shuttle Fatally Flawed
Prague - Mar 3, 2003
After the recent loss of the Space Shuttle Columbia, Americans and Israelis are mourning the tragic deaths of the seven-crew members. This is a tragedy not only for them but also for all of us, because the brave astronauts sacrificed their lives for the progress of all mankind.
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