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#1 Re: Interplanetary transportation » Project Noah (Big cousin of Project Orion) » 2006-07-10 08:16:32

If James Blish were still alive he would offer the Wagoner Gravitron-Polarity Generator(SPINDIZZIE!). Perfect for the job! Actually Orion relied upon the well-known hollow charge principle to direct an explosion-path of least resistance et-al.  Presumably it's merely a matter of magnitude: high-yield fusion devices in place of (relatively) low-yield fission types of Orion. Proviso: OUT IN SPACE! With the required number of devices needed for a city to exit the Earth's gravity-well, the consequent massive release of neutrons should insure an unmanned vehicle & launch area;not to mention Planet!  :twisted:

I so wish I new how to calculate the fallout to the crew and the planet. I currently lack much of the knowledge needed to design and analyze the optimal Orion ship. I think the greater concern is the health of the crew rather then the health of the planet as numerous fusion devices have already been detonated on earth without any dramatic effect on the world environment.

Or so we're told! To merely move say, a 100,000T ship out of the gravity-well of Earth will require a minimum of 64Million Megatons of force: a fair # of T-NDs. Imagine a city weighing a 1000 times that. I don't think Crew health is too much of a problem - apart from the huge quantities of polystyrene & polyethelene required behind the blast plate to deflect and absorb , alpha, beta & gamma rays, not to mention neutrons. But for those in the direct path.... Mark you, space itself is loaded with radiation of every known variety, making the term "space" somewhat of a misnomer! wink

#2 Re: Interplanetary transportation » Ares V (CaLV) - status » 2006-07-08 23:08:35

GCNRevenger wrote:

Apparently you haven't been following the discussion about SRB safety nor has it even occured to you that there is another and very important variable to consider when designing rockets..."/quote

What discussion: I joined under two weeks ago. Still exploring the site for interesting threads.You're making assumptions on the basis I haven't mentioned other factors. That does NOT mean I 'm not aware of any/them.

Quote/ First of all, the Shuttle SRBs, by virtue of their fuel blend  have a handy little characteristic: if they leak, they stop burning. The solid fuel only burns rapidly when it is under pressure, so if there is a leak the pressure drops and the combustion slows down. Solid fuels themselves also cannot explode, since the rate of combustion is intrinsicly controlled by the surface area. Modern solid fuels are imbedded in hard rubber, so there is no possibility of a sudden radical increase in surface area or burn rate. Pop-off caps using venerable explosive bolts on the sides would also provide shut down options."

Oh yes they can explode matey! Ask any Range Safety Officer! PBAN is as volatile as any other SP in the right circumstances. And it is by NO MEANS a new SP combination. Use it myself in my own H-PR's. LOT's going for it. You would need a pretty substantial "leak" to engender the pressure drop characteristics you describe: and they would by no means be consistent. In any case that pressure you speak of is a function of propellant burn, and the surface area as we both know, constantly varies, hopefully with some consistency - mute point , since it usually doesn't, which is why a large performance margin in the SRB has to be catered for elsewhere. Actually the rate of combustion depends upon the burn occuring over the entire constantly varying internal surface area from top to bottom; in effect enlarging the central hole once the star-spigots burn off; in the initial stages. Which, in of itself,implies a pressure drop through increased csa! Hence the regressive thrust characteristics of most solid motors, except those employing a 'D' core design.  That asymmetric design also has it's risks...
In any case, as we saw from Challenger, a leak DOES NOT prevent a solid motor from continuing to burn. If it did, the effect in of itself could result in a CATO. The other one is still burning...get it...? Granted that wouldn't apply to "The Stick", but certainly to Ares 5...

QUOTE/ Second, thanks to their sturdy steel construction, if there is a leak around
a segment seal it won't lead to a catastrophic explosion like smaller light-weight SRBs. The SRB has sufferd at least two leaks, first with Challenger and a second with Atlantis, but in both cases the SRBs did not explode. In the latter case Atlantis was able to continue on to orbit as the leak didn't face the tank or orbiter."

Do remember that a solid motor is intrinsically a controlled explosion in of itself. Explosive gases seek the path of least resistance first, so your thrust vector takes on an asymmetric characteristic which has the potential of becoming uncontrollable. It is just that "sturdy" construction that give the segmented SRB it's low structural efficiency. It is the marginal performance predictions that require compensation in the other stages for M.O.E purposes.

Quote/Since the CEV and its upper stage will be riding on top of the SRB's one-piece steel end cap, no segment seal leak can threaten it. If there is a leak, it will also be obvious and easy to detect since there would be a sudden loss of thrust.

A very good argument for the fallacy of the side-by-side booster/payload configuration! Nonetheless, I don't agree for reasons iterated earlier.

QUOTE/Compare this with a liquid engine, any liquid engine, and these are compelling advantages. Reguardless how its arranged, liquid fuels will always have the possibility of exploding, while the solid fuel doesn't. All modern high-performance liquid engines are also turbopump driven, which carry inherint and "unfixable" safety concerns. When they fail, they usually fail big (maybe ignite the fuel too), and it doesn't take much to tear up a turbine spinning thousands of RPMs cooled to cryogenic temps.
Many high-performance engines also operate at very high chamber & nozzle pressures/temperatures that stretch materials to the limits, increasing the risk of catastrophic failure and the severity of the failure if it does occur. Liquid fueled engines are also much harder  to instrument and monitor to provide sufficent warning to shut down or use the crew escape systems, there is little warning when a turbine is about to come apart and monitoring the temperature all around the nozzle would be difficult."

Known quantities(for decades), and characteristic of ALL liquid motors including the J2-X and CEV PM of the ARES 1 &V upper stages. But I would remind you that both the Saturn's SI-c and Blue Streak booster stages each had a perfect launch record. As for the instrumentation; standard stuff! How do you think they evaluate Test Flights;guesswork? Just image the SIZE of the vehicle if THOSE were solids for just the very reasons you've outlined. A falacious argument at best. To my mind, the solids are an okay solution, but in terms of optimum performance/overall cost, don't cut the mustard.

QUOTE/ Eliminating the possibility of these occuring with added headaches involved with man-rating and instrumentation in one of the two stages of the CLV is a major bennefit. There is one more bennefit that SRB has that isn't technically related to the engine, that is because of the very high thrust the CLV can accelerate more quickly than an EELV-style liquid fueled rocket which improves the safety by getting off the pad and to orbital velocity faster."

That high thrust only lasts for so long - in the initial stages - such that SRM stage burn-out velocity is usually 1000/1500fps down in deltaV in comparison with a LP Booster, leaving the upper stages with much more work to do.  More than offsetting the high initial acceleration:which is merely a function of Thrust to Weight ratio in any case.

QUOTE/This is good, especially for ISS missions, since if you have to ditch in the sea you can do so closer to shore and further south in warmer water than if you accelerated slowly, plus if you get pretty close to orbit the CEV's extra fuel might permit a once-around abort that avoids a hypersonic backflip in the atmosphere with normal parachute deployment in the US."

"Uh Huh"! By the way, the ditching criteria is as much a function of the trajectory parameters as the launcher characteristics itself; particulary with respect to hi-LEO ISS type orbits, where a steep trajectory is employed with downrange distance being markedly reduced.
An atmospheric "hypersonic backflip"!? Do me a favor! A partial orbit scenario has been/is built into every manned launch trajectory in both the U.S and Russia(I remembered!) from the beginning. Even if Orbital Velocity is not achieved, a spacecraft will re-enter much as an ICBM would - with possibly more control. 

Your other points aside, the leak/outgassing from the segment joint on Challenger began 180degrees away from the ET/Orbiter also. All the video footage shows that. Which was why I began thinking NASA's explanation of the incident was suspect. As with Columbia, where the video clearly shows the eco-foam chunk hitting the wing well abaft of the lower leading edge and disintegrating down the underside of the wing. Whereas the "experiment" clearly was a direct hit upon the upper surface  the wing leading edge itself.
As for your point re the time to orbit, any advantage of initial acceleration is more than offset by the intrinsic long burn time of the J2-X  LOX/LH2 stage which burns out at only 63miles altitude, leaving the CEV propulsion module with some 120 miles of altitude to gain - 65% of total: in vacuo, granted. No indicator of the deltaV component required. Most orbital trajectories make the penultimate stage achieve the highest altitude fraction, with - 3+stage configuration - the final stage(s) merely doing kicker duties with usually only a slight altitude gain.
I haven't plugged ARES 1 into  my software yet, since accurate mass fractions/structural efficiency and RSRB criteria haven't been provided on the data I have access to(unless the original RSRB is being ressurrected..right! Fudge factors! Why not! Mark Wade to the rescue!), but the CEV PM must have massive reserves to achieve such a huge climb all on it's own.

#3 Re: Planetary transportation » Bikes on Mars? - Don't laugh! » 2006-07-08 09:35:10

Didn't see it here, nor on any other site (didn't  look too hard, though)

Considering bikes are *the* single most effective non-motorised way of getting somewhere, wouldn't it be worthwhile to think about them?

Ok, it's a funny idea, guys 'n gals in suits on a bike, but those things are fairly cheap, simple to repair etc...

you could make three-wheelers with an extra cart, if you wish, and they'd double as excercise equipment, too.

imagine a base with semi-well cleaned 'roads', wouldn't it be simpler to take a quick jump on a bike to the nearest reactor, powerplant, whatever, it being half a mile away...if you take a buggy, you have to check the engine and stuff, plus they weigh a *lot* (transport to Mars) compared too a sturdy bike.
you could ship dozens, insttead of one, two personal mini-rovers...
has there been experiments, and if not, why not? People afraid of being laughed at? The current suits much too stiff to do that?

It's a great idea...except any manual expenditure of energy requires oxygen. On Mars the bike would need to have a reserve supply - which would increase the weight of the bike...resulting in great energy expenditure...so a solar-electric /boosted powered bike would be probably better: especially if loads have to be carried. But it will be lighter and simpler than a four-wheeled vehicle, that's for sure 8)

#4 Re: Interplanetary transportation » Ares V (CaLV) - status » 2006-07-08 07:57:16

Seven RS-83s wouldn't have enough thrust to launch a Saturn-class heavy lifter, and the fuel tank(s) would be so large that assembly would be difficult. So if you used Delta-IV style strap on booster cores with RS-83s in them, why bother use SRB instead? Sure you'd get some performance boost with the higher Isp the RS-83 would offer, but the engine still needs several hundred million or a few billion for development, and would probably cost more per-launch than a quintet of RS-68s. The RS-83 also weighs 13MT each versus the RS-68 ~7MT.

RS-84 is probably a fine engine, but you gotta compare its performance to the cost of SRB. The Shuttle SRBs are pretty cheap for the thrust they provide, and are very reliable. The single SRB on the Ares-I provides unique safety features, so since we are going to use it then we might as well use it for the bigger Ares-V too instead of developing a liquid kerosene booster. Maybe sometime down the road, when we are supplying/building a Mars base, then a reuseable flyback booster for Ares-V would be a good idea.

In fact, it was the RS-84(and not the RS-83 LOX/LH2 engine) for the first stage booster that I referred to. 7x 1,064,000lbf = 7,448,000lbf; a mere tad below 5xF-1’s and retaining a +12% ISP advantage throughout.
Due mainly to a massive differential in propellent density, LOX/RP1 has an advantage versus the LOX/LH2 combo for booster stages: particularly utilizing the superior liquid propellant engine technology of the Russians - which both the RS-84 & P+W RD-180(the latter being an americanised RD-170: reason it was rejected) do! In any case the structural efficiency of a solid motor is WAY below that of a C.P Booster: especially if one employs the (originally Russian) Al-Li alloy structure technology. A 2Mlb/ 309’(?!) vehicle to loft 12-13T to a 185ml orbit? An efficient LP design would be at least 65% of that; look @ Proton. I'd really like to hear the "unique safety features" an SRB has! ANY failure in a solid motor always means a CATO – as I know to my own cost at LRDS/NERO et al the hard way! Brave boys and girls, those Astronuts!  tongue

#6 Re: Interplanetary transportation » Ares V (CaLV) - status » 2006-07-06 22:09:19

Uh, specific impulse is pretty much intrinsic to the engine. SSME (RS-25) has much better specific impulse at altitude than RS-68, but bigger tanks with RS-68 provides the same lift capacity for less money. Also worth noting, that the final Ares configuration that featured SSME used five of them, not four.

The RS-83/84 are suited for RLVs, not for expendable boosters. Since we aren't building an RLV for, oh, thirty years or so then canceling them was a good choice. We already have engines that are good enough for VSE.

You're right. I'd forgotten the '68's vacuo ISP was about 12%less. Enough to make a difference. Still a lot cheaper in unit cost terms. Don't agree about the 83/84; particularly the latter. Seven of em would have given us a nice first stage to play with.  Building that kind of reliability into a rocket engine is by no means a bad thing - especially with man-rating et al. Plus using LOX/LH2 in the first stage almost precludes the use of solid strap-ons. The RS84 was a hi-performance/thrust LOX/RP1 design: not too heavy either. Downgrading to EELV standards would not have been a problem. Unless - heaven forbid - we use the Sov-I mean Russian engines of the Atlas ala Energia! but since the ISS is really MIR 2, why not!? smile

#7 Re: Interplanetary transportation » Ares V (CaLV) - status » 2006-07-06 08:37:04

Hopefully this will tie all the CaLV threads together

This report in Flight International says the RS-68  has been selected as the CaLV’s main engine!

Life-cycle cost also drove selection of the Rocketdyne RS-68 as the CaLV’s main engine, rather than the RS-25e. However, this led to an increase in CaLV core structure diameter from 8.38m, the same as the Shuttle’s external tank, to 10m. The wider core was needed to enlarge the fuel tanks to provide the extra propellant required to allow the RS-68 to burn long enough to deliver RS-25e-like performance.

Actually the total specific impulse value of 4x RS-25e burning for a given time can be met by the the more powerful RS-68 with a shorter burn time and trajectory tuning to suit. I imagine though, that the thrust frame for 5xRS-68 will be heavier mass-wise than for 4xRS-25e. More mass: more propellant to compensate!

#8 Re: Interplanetary transportation » Using the shuttle's external tanks as spacecraft » 2006-07-06 07:58:43

They built a shuttle launch base in southern California and trashed it after blowing billions on it.  Can't these guys make up their minds and stick with something!

Hmm, If I remember correctly, Vandenburg AFB was around before the shuttle, and is still in very good shape, and the STS launches would have only been a small part of the mission there.

I think most of the facilities they built are still there, but Vandenburg was meant for military flights, not civilian flights (for a higher polar orbit).  Since the Air Force doesn't want the shuttle anymore, there's no need to launch from Vandenburg.

Vandenburg would be useless for anything other than polor orbit launches, for safety reasons.  If there was an accident like Challenger, toxic substances would be sprayed all over California, Nevada, Utah, Colorado, Arizona, New Mexico, and I'm sure a few other states.  A polar launch would take it along the coast line and over the ocean, however.  In addition, I remember there being some safty issues with the launch itself (like sound waves bouncing off the near-by hills, and stuff like that).

Oddly enough, the facilities have been modified to accommodate EELV launches w/classified payloads. I worked on it back in the early '90's. The safety issues - apart from the old N2O4/UDMH toxicity conundrum - are irrelevent since the Challenger "incident" was intended as a warning(Star Wars et al): the REAL reason USAF shuttle ops were cancelled & Titan IV hung on so long.  Go Atlas, Delta...and Soyuz!

#9 Re: Interplanetary transportation » Ares V (CaLV) - status » 2006-07-06 07:35:17

Ten meters? This is sounding more and more like the ol' Saturn-V's planned sucessors that used solid rocket boosters instead of the massive F-1 first stage.

Well…Griffin said that the Apollo engineers did a lot right.

Actually it wasn't so much the Apollo engineers as the USAF for initiating and funding the F-1 engine in the first place: 1957-8! Without that, it would have been a US N1 type nightmare with 30-40 engines for the launch vehicle. Or Von Brauns' initial EOR technique using multiple launches.  Mind you why NASA scrapped the RS-83 & 84 motors is an example of how they've given the impression they've lost their way...3 years to do 16 STS launches: a rate they never achieved even during the heyday

#10 Re: Interplanetary transportation » Project Noah (Big cousin of Project Orion) » 2006-07-04 10:40:45

If James Blish were still alive he would offer the Wagoner Gravitron-Polarity Generator(SPINDIZZIE!). Perfect for the job! Actually Orion relied upon the well-known hollow charge principle to direct an explosion-path of least resistance et-al.  Presumably it's merely a matter of magnitude: high-yield fusion devices in place of (relatively) low-yield fission types of Orion. Proviso: OUT IN SPACE! With the required number of devices needed for a city to exit the Earth's gravity-well, the consequent massive release of neutrons should insure an unmanned vehicle & launch area;not to mention Planet!  :twisted:

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