A kerosene-fueled X-33 as a single stage to orbit vehicle.
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From: Jeff Findley on 22 Mar 2010 13:55 "J. Clarke" <jclarke.usenet(a)cox.net> wrote in message news:ho7rdn12inj(a)news7.newsguy.com... > SSTO, if it can be done at all with chemical fuels, is _barely_ doable. There are several expendable stages which could theoretically do SSTO, with a usable payload, if launched by themselves. Note that Atlas was able to put Mercury into orbit, but it did cheat a bit by dropping the two outer engines on the way up, partly to reduce thrust and partly to reduce the dry mass of the booster. That said, a resuable SSTO is a matter of debate. Some say it's possible, others say it's too hard or impossible. Jeff -- "Take heart amid the deepening gloom that your dog is finally getting enough cheese" - Deteriorata - National Lampoon
From: Jeff Findley on 22 Mar 2010 13:56 "J. Clarke" <jclarke.usenet(a)cox.net> wrote in message news:ho7rdm02ink(a)news7.newsguy.com... > On 3/22/2010 8:32 AM, Jeff Findley wrote: >> "Greg D. Moore (Strider)"<mooregr_delet3th1s(a)greenms.com> wrote in >> message >> news:X6-dnTN9SfCfDzvWnZ2dnUVZ_rWdnZ2d(a)earthlink.com... >>> J. Clarke wrote: >>>> Why do people think that launching from 50,000 feet will help somehow? >>>> Going into orbit is not a matter of going high, it's a matter of going >>>> _fast_. Launching from 50,000 feet or from sea level you still need >>>> to impart 18,000 miles an hour of delta-v. That's the hard part. >>> >>> Because 50,000 feet gets you above the bulk of the atmosphere which >>> provides a decent bonus. >> >> Specifically, you can optimize your engines for the much lower pressure >> of >> 50,000 feet (to vacuum), as opposed to the compromises necessary to make >> them run at sea level. > > So how much do you think this gains you? For a conventional bell engine design, quite a bit of ISP as you can optimize the engine bell shape for vacuum. Jeff -- "Take heart amid the deepening gloom that your dog is finally getting enough cheese" - Deteriorata - National Lampoon
From: J. Clarke on 22 Mar 2010 14:04 On 3/22/2010 12:01 PM, hallerb(a)aol.com wrote: > On Mar 22, 10:54�am, "J. Clarke"<jclarke.use...(a)cox.net> wrote: >> On 3/22/2010 10:20 AM, hall...(a)aol.com wrote: >> >> >> >> >> >>> On Mar 22, 9:12 am, "J. Clarke"<jclarke.use...(a)cox.net> �wrote: >>>> On 3/22/2010 4:07 AM, Pat Flannery wrote: >> >>>>> On 3/21/2010 4:53 PM, Marvin the Martian wrote: >> >>>>>> It is apparent you're not acquainted with rocket science. Getting through >>>>>> the "dense lower atmosphere" is no big deal. Von Braun did that with an >>>>>> single stage alcohol fueled rocket 65 years ago. >> >>>>>> The problem is getting up to orbital velocity. >> >>>>> If you can put the LOX aboard the rocket at altitude, where the humidity >>>>> is very low, you can eliminate the weight and complexity of having to >>>>> put insulation on the outside of the oxidizer tank section, as ice won't >>>>> form on it like it would if it were fueled and launched from the >>>>> surface. Not only does the booster then end up carrying the weight of >>>>> ice still sticking to it during ascent, but the ice that sheds can >>>>> damage the booster due to its mass and impact speed. >> >>>> So how much "weight and complexity" is involved with a little bit of >>>> spray-on foam? And in practical terms how much difference is this going >>>> to make? I'm sorry, but you're trying to reduce launch costs by >>>> tackling an at best second order effect without dealing with the major >>>> cost drivers. In any case the tankage on the X-33 is does not have >>>> surfaces exposed to the airflow so this becomes a non-issue. >> >>>> And if you're talking an X-33 it has to have a thermal protection system >>>> for reentry anyway. >> >>>> And the X-33 could not achieve more than half of orbital velocity on >>>> HYDROGEN so how in the Hell do you expect it to do that with kerosene? >> >>>> SSTO, if it can be done at all with chemical fuels, is _barely_ doable.- Hide quoted text - >> >>>> - Show quoted text - >> >>> If you call the airplane a non stage since it basically flies up to >>> release altitude then flies back to base. >> >>> A SSTO where the only stage is a orbital one is very doable. >> >> What does that sentence mean? �If it is single stage to orbit then there >> is only one stage and since it achieves orbit it is necessarily "orbital". >> >> But your assertion does not convince. �You are posting on the Internet. >> � Most people posting on the Internet have opinions. �Most of those >> opinions are ignorant twaddle. �So one must take your opinion as >> ignorant twaddle until you can provide some numbers to go with it. >> >>> espically since you dont have to carry ALL the fuel from the launch >>> pad to orbit. >> >> So where do you carry it? �Is Spock beaming it into your vehicle with >> the transporter or something? >> >>> with in flight refueling along the way it is a real winner. >> >> So how do you refuel it in flight? >> >>> no loaded bomb launch either:) >> >> So when does the "bomb" get "loaded" and how does that happen? >> >> Show me the numbers on your airliner-launched SSTO. �All that your >> airliner brings to the party is a portable launch pad. �Its effect on >> the performance requirements is negligible.- Hide quoted text - >> >> - Show quoted text - > > Lets make it SIMPLE for you.... > > A large airliner with little fuel takes off, low fuel level keeps take > off weight down:) > > with multiple in flight refuels, done every day in the military:) gets > the vehicle to near release altitude. And that gains you what? Your SSTO still has to have enough fuel and oxidizer aboard to impart 18,000 miles an hour of delta-v. > at this point the airliner sets off its afterburners and releases the > actual rocket stage, which achieves orbit. The only airliners with afterburners are the Concorde and the TU-144, neither of which under any circumstance can lift an X-33. In any case, what do you believe that afterburners accomplish? > the airliner flies back to base 100s if not a 1000 miles away. And this gets you into orbit how? The question is not whether an airliner can fly around with something attached to it, the question is whether that thing that is attached can somehow achieve orbit. You have not even attempted to address that question. > a fully fuled rocket sitting on the pad is basically a loaded bomb. > > a airliner launched rocket stage can use ejection seats for the > airliners crew, and a capsule safety pod for the rocket stage crew. And what does this gain you? Does the crew jump out before the SSTO actually starts for orbit or something? If your SSTO is to achieve orbit at some point it has to become that "loaded bomb" that you fear and if it is to take a crew into orbit then they have to be aboard that "loaded bomb" that you fear, so how does attaching that loaded bomb to an airliner change anything? > think out of the box, the box isnt your friend.............. So show us the numbers that demonstrate that your "out of the box" solution will work. Oh, but that is that stupid boring math that is only for stupid boring nerds and not for brilliant people like you, right?
From: J. Clarke on 22 Mar 2010 14:17 On 3/22/2010 3:07 PM, Pat Flannery wrote: > On 3/22/2010 6:54 AM, J. Clarke wrote: >> But your assertion does not convince. You are posting on the Internet. >> Most people posting on the Internet have opinions. Most of those >> opinions are ignorant twaddle. So one must take your opinion as ignorant >> twaddle until you can provide some numbers to go with it. > > Yeah...but you are posting on the internet also, and I'm not seeing any > numbers so far. :-D I'm asking the person making the assertion to back it up. He is proposing that a kerosene-fueled X-33 attached to an airliner can somehow achieve orbit. I want to know how that is going to work. What we know: The X-33 was not designed to achieve orbit even with a hydrogen-oxygen rocket. <http://www.nasa.gov/centers/marshall/news/background/facts/x33.html> Note maximum speed Mach 13. That is per <http://www.aerospaceweb.org/design/scripts/atmosphere/> approximately 7500 knots true airspeed or about 8500 miles per hour. Orbital velocity is approximately 18,000 miles/hr at 120 miles altitude per <http://hyperphysics.phy-astr.gsu.edu/HBASE/orbv3.html>. While I'm not going to give a cite for it, it is generally accepted that all else being equal a kerosene rocket will have lower specific impulse than a hydrogen rocket, so whatever performance the X-33 achieves with a kerosene rocket will be less than for a hydrogen rocket. So, tell me, how do you manage to get that additional 10,000 miles per hour out of sticking the thing on top of an airliner?
From: Jeff Findley on 22 Mar 2010 14:37
"J. Clarke" <jclarke.usenet(a)cox.net> wrote in message news:ho8cvh2rfj(a)news6.newsguy.com... > While I'm not going to give a cite for it, it is generally accepted that > all else being equal a kerosene rocket will have lower specific impulse > than a hydrogen rocket, so whatever performance the X-33 achieves with a > kerosene rocket will be less than for a hydrogen rocket. ISP is one measure of engine performance. Vehicle performance is much more complicated and depends on many more variables besides engine ISP. In particular, LH2 isn't very dense. Kerosene is far more dense than LH2 plus it doesn't need cryogenic storage. In a vehicle design, kerosene has some distinct advantages which may make up for its lower ISP. Jeff -- "Take heart amid the deepening gloom that your dog is finally getting enough cheese" - Deteriorata - National Lampoon |