A kerosene-fueled X-33 as a single stage to orbit vehicle.
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From: Robert Clark on 26 Mar 2010 14:05 On Mar 25, 11:29 am, Pat Flannery <flan...(a)daktel.com> wrote: > > So other than proving a philosophical point, the SSTO version doesn't > give you any real advantage. > The SSTO Titan II is an interesting concept (assuming it really could do > that - that 25/1 mass fraction seems off), but one has to ask oneself if > you could use a smaller two-stage rocket of lower cost to orbit the same > usable payload weight as the Titan II's first stage? > Note that the descriptions of the SSTO Titan II don't even talk about it > carrying a payload, just putting itself into orbit. Ed Kyle who maintains the site SpaceLaunchReport.com is a good source for the specifications on rockets so these numbers on the Titan II should be pretty accurate: Space Launch Report: Titan 23G Data Sheet. http://www.spacelaunchreport.com/titan2.html His numbers for the Titan II also amount to about a 25 to 1 mass ratio for the first stage. The example of the Titan II first stage explains well the idea behind using dense propellants. The aerozine fuel used for the Titan II was even denser than kerosene, and the nitrogen tetroxide used as the oxidizer was denser than LOX. But this propellant combination resulted in a lower Isp than high performance kerosene engines had, only in the range of 300 s vacuum. This means the Titan II needed a higher mass fraction. But because the propellant was denser this was easy to achieve. Another key factor explained well by the Titan II case is the much better T/W you can get with the denser propellants. As I said the aerozine/nitrogen tetroxide propellant is denser than kero/LOX. This resulted in a T/W for the Titan II engines even higher than for kerosene at 155 to 1(!) And some later engines used on the Titan 3 and Titan 4 using this same propellant combination were able to get a thrust/weight in the 164 to 1 range. One wonders if we could get even better results by using even denser propellants. Bob Clark
From: Robert Clark on 26 Mar 2010 14:18 On Mar 26, 9:38 am, Marvin the Martian <mar...(a)ontomars.org> wrote: > ... > > And that's how humans launch rockets to LEO now, from airplanes. Oh wait! > You don't do that. You launch them from the ground. > >... Don't forget the air-launched Pegasus system. Bob Clark
From: Pat Flannery on 26 Mar 2010 23:25 On 3/26/2010 9:20 AM, Marvin the Martian wrote: >> Similar to Sea Launch, only you can put your launch vehicle into just >> about any orbit on *much* shorter notice with a C-5B than you can with a >> converted oil drilling platform. > > As if "short notice" is an issue since satellite planning usually takes > years anyway. > For military satellites it can be, as either a dangerous situation develops somewhere in the world and you a reconsat imagery of it ASAP, or one of your critical satellites dies (or is destroyed by someone) and you need to replace it ASAP. The air-launched Pegasus booster is capable of carrying eight small military communications satellites aloft on a single launch, with them stacked up like pancakes in the nose: http://space.skyrocket.de/index_frame.htm?http://space.skyrocket.de/doc_sdat/mublcom.htm Pat
From: J. Clarke on 26 Mar 2010 23:43 On 3/26/2010 11:25 PM, Pat Flannery wrote: > On 3/26/2010 9:20 AM, Marvin the Martian wrote: >>> Similar to Sea Launch, only you can put your launch vehicle into just >>> about any orbit on *much* shorter notice with a C-5B than you can with a >>> converted oil drilling platform. >> >> As if "short notice" is an issue since satellite planning usually takes >> years anyway. >> > > For military satellites it can be, as either a dangerous situation > develops somewhere in the world and you a reconsat imagery of it ASAP, > or one of your critical satellites dies (or is destroyed by someone) and > you need to replace it ASAP. > The air-launched Pegasus booster is capable of carrying eight small > military communications satellites aloft on a single launch, with them > stacked up like pancakes in the nose: > http://space.skyrocket.de/index_frame.htm?http://space.skyrocket.de/doc_sdat/mublcom.htm That's nice. Can it put them in different orbits?
From: Pat Flannery on 27 Mar 2010 08:43
On 3/26/2010 7:43 PM, J. Clarke wrote: >> For military satellites it can be, as either a dangerous situation >> develops somewhere in the world and you a reconsat imagery of it ASAP, >> or one of your critical satellites dies (or is destroyed by someone) and >> you need to replace it ASAP. >> The air-launched Pegasus booster is capable of carrying eight small >> military communications satellites aloft on a single launch, with them >> stacked up like pancakes in the nose: >> http://space.skyrocket.de/index_frame.htm?http://space.skyrocket.de/doc_sdat/mublcom.htm >> > > That's nice. Can it put them in different orbits? I doesn't need to; the idea is to put up small military comsats faster than an enemy can shoot them down, in a analogy to a MIRV missile system. As the satellites are deployed, the carrier stage will slow down a bit do to action-reaction on each release, so that they will spread out along a particular orbit. Each will take a independent ASAT to destroy, so it becomes economically unfeasible for an enemy to deploy enough ASATS to be able to keep up with the rate the comsats can be surge launched at, though they could be destroyed via a high-energy ground-based laser system. When those get into large-scale worldwide deployment though, all of LEO will be very unhealthy for every country. Pat |