A kerosene-fueled X-33 as a single stage to orbit vehicle.
in [Physics]
|
Prev: JSH:Twin primes probability correlation
Next: SpaceX says Falcon 9 rocket test fire is a success
From: J. Clarke on 23 Mar 2010 14:05 On 3/23/2010 4:25 PM, Pat Flannery wrote: > On 3/23/2010 6:52 AM, J. Clarke wrote: >>> Henry Spencer did the math for several existing rocket stages. What most >>> needed to make this happen would be a deeply throttlable engine. Atlas >>> was >>> an example. From memory, one of the Titan II stages and I think one of >>> the >>> Saturn V stages also had the appropriate mass fraction. >>> >>> If you do the math an expendable SSTO isn't really that hard. >> >> So why are they not in common use? > > Because of the low payload that they can carry into orbit versus the > overall cost of the vehicle. > If adding a second stage increases vehicle cost by 75% but allows you to > put twice as much weight into orbit, then your price-per-pound into > orbit is lower than using a SSTO launcher. In other words they can barely struggle into orbit rather than being "not that hard".
From: Michal Jankowski on 23 Mar 2010 15:02 Pat Flannery <flanner(a)daktel.com> writes: >>> If you do the math an expendable SSTO isn't really that hard. >> >> So why are they not in common use? > > Because of the low payload that they can carry into orbit versus the > overall cost of the vehicle. ....because nobody even tries to build them, and that's mostly because nobody's ever built any. http://sci.tech-archive.net/Archive/sci.space.history/2007-07/msg00146.html MJ
From: Marvin the Martian on 24 Mar 2010 22:24 On Mon, 22 Mar 2010 00:07:30 -0800, 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. > > Pat If pigs could fly, then you could tie an apple to your rocket and have them take your rocket to space. Yeah, right. You're going to dock with a refueling rocket to send up the oxidizer on an accelerating rocket for the brief moments that it is on it's way up. That problem has been addressed by staging the rocket. The "refuel" rocket is the first stage. Now get real.
From: Marvin the Martian on 24 Mar 2010 22:33 On Mon, 22 Mar 2010 09:01:31 -0700, 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. > > at this point the airliner sets off its afterburners and releases the > actual rocket stage, which achieves orbit. > > the airliner flies back to base 100s if not a 1000 miles away. > > 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. > > think out of the box, the box isnt your friend.............. You're an idiot, spouting off about something you're utterly ignorant and not even bothering to check out the physics. I'm all for THINKING out of the box, but totally against drug induced delusional monkey gibber. To get to orbit, your minimum speed is 7 km/sec. The fastest airplanes can travel about .9 km/sec, and those are fighter jets, not tankers. You're talking about an energy difference of 7^-0.9^2 = 49 - 0.8, or 0.8/49 =~ 2%. And for that piddly advantage, you have to including docking, refueling hardware, and screw around with transferring CRYOGENIC liquid oxygen at super sonic speeds. That's just stupid on the face of it.
From: Marvin the Martian on 24 Mar 2010 22:48
On Mon, 22 Mar 2010 14:37:29 -0400, Jeff Findley wrote: > "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 The paper I read on kerosene rockets argued that the rocket mass was increased so much because of the size of the liquid hydrogen tank and compressors to keep it liquid such that you could actually loft more payload (but less total rocket mass) with a kerosene rocket than a hydrogen one, since kerosene requires no pumps, no insulation, a smaller tank, and far less support structure than liquid hydrogen does. The paper made sense. This thread doesn't make sense. It is just absurd statements put out by some gibbering wannabe posers. The same arguments for staged rockets rather than single stage to orbit still stands. The gibber about transferring LOX in the boost phase is just stupid unthinking gibber. |