A kerosene-fueled X-33 as a single stage to orbit vehicle.
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From: Marvin the Martian on 21 Mar 2010 20:53 On Sun, 21 Mar 2010 11:39:31 -0700, hallerb(a)aol.com wrote: > On Mar 21, 11:49�am, "J. Clarke" <jclarke.use...(a)cox.net> wrote: >> On 3/21/2010 10:42 AM, hall...(a)aol.com wrote: >> >> > Why take along EVERYTHING for a SSTO when the vehicle could use a >> > airplane to get the in orbit portion to at least 50,000 feet above >> > most of the atmosphere, not tied to a single launch location, fly the >> > airplane to a convenient launch location, fuel to get to 50,000 feet >> > can be from tanker refueling along the way.......... >> >> > granted for a really large payload a BIG HUGGER AIRLINER might need >> > to be a custom build, but the upsides are huge. >> >> > no risky loaded bomb launch being the first. >> >> > SSTO is just a distraction from the more important...... >> >> > LOW COST TO ORBIT!! >> >> 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. > > the hardest part is having enough fuel onboard to get you thru the dense > lower atmosphere.those large tanks weigh more. 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. > with a aircraft first stage that part is taken care of by a mature well > understood technology, and since in air refueling to release altitude > would be used lots of unnecessary mass wouldnt need lifited off the > pad.. > > plus the aircraft with space plane could be released at the equator > gaing some margins too. and bad weather would be much less of a issue. > no more storm clouds nearing pad troubles. just fly a few hundred miles > away to a nice clear area. > > its far easier to accelerate a lower mass object, the
From: Pat Flannery on 22 Mar 2010 04:07 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
From: Jeff Findley on 22 Mar 2010 08:32 "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. 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 09:12 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.
From: J. Clarke on 22 Mar 2010 09:17
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? |