Single-Stage To Orbit still appears out of reachto many engineers, with the exception of the hypotheticalHOTOL/Skylon concepts.But Project Score in December, 1958, using a 1-1/2 stage Atlasbooster, may have showed how it can be done by a conventional booster; at least for a small payload on a proof-of-conceptlaunch-flight. The original Atlas of course was basically a stainless-steel 'balloon'with three rocket motors at launch. Too generic a definition, huh?Maybe. The original Atlas' stainless steel shell was no where thickerthan a quarter, and on average almost as thin as a dime. The Project Score Atlas weighed about 182,000 Ibs fully loaded;and was about 8600 Ibs empty in orbit, minus the 150 Ib payload.Minus the weight of the sustainer rocket motor (1010Ibs?)Minus the weight of its pumps, pressurizing tanks, vernier rockets and fuel tanks, transistorized avionics and inertial guidance systemthe stainless steel shell would have probably been around6,500Ibs weight, give or take a couple of hundred pounds. Thing is?..There was no epoxy-kevlar, nor graphite-epoxy compositeback then. There was no lightweight laser gyroscopic IGS, nor were there lightweight titanium rocketmotors (The 1958 Atlas had special steel alloy or stainless steel rocket motors; heavy by today's standards).And the Project Score Atlas did not have primary engines that werethrottled by avionics. So how much weight could have been saved by replacing the thinstainless steel shell with a teflon-coated epoxy-kevlar or epoxy-graphiteshell?2000Ibs saved?4000Ibs?...I think this value is possible.How many pounds would have been saved by replacing the steel in the Atlas rocket motors with titanium? You do the math.So a modernized Project Score Atlas could become an SSTO vehicle capable of putting a small payload into orbit, even if it meant haulingall three of its primary motors into orbit?What do you think?
So how much weight could have been saved by replacing the thinstainless steel shell with a teflon-coated epoxy-kevlar or epoxy-graphiteshell?
nor were there lightweight titanium rocketmotors (The 1958 Atlas had special steel alloy or stainless steel rocket motors; heavy by today's standards).
Here is something to chew on, Making a few assumptions about TAN,, the same thrust as the the stage and a half plus sustainer could be produced with just the sustainer in about the same mass as the sustainer.Pure fantasy, but still interesting.Do not forget, the Atlas also placed itself with the much heavier mercury capsule in orbit.
Quote from: kevin-rf on 04/30/2010 02:45 amHere is something to chew on, Making a few assumptions about TAN,, the same thrust as the the stage and a half plus sustainer could be produced with just the sustainer in about the same mass as the sustainer.Pure fantasy, but still interesting.Do not forget, the Atlas also placed itself with the much heavier mercury capsule in orbit.With balloon tanks and a modern TAN-like engine, I think you could do SSTO, possibly with enough margin to make it fully reusable. A modern TAN engine, done right could have much better vacuum performance than the Atlas sustainer, without having to carry the mass of the booster engines even for the first bit of the flight.~Jon
Single-Stage To Orbit still appears out of reachto many engineers, with the exception of the hypotheticalHOTOL/Skylon concepts.But Project Score in December, 1958, using a 1-1/2 stage Atlasbooster, may have showed how it can be done by a conventional booster; at least for a small payload on a proof-of-conceptlaunch-flight. The original Atlas of course was basically a stainless-steel 'balloon'with three rocket motors at launch.
Build our CNT elevator.
Quote from: jongoff on 04/30/2010 04:38 amQuote from: kevin-rf on 04/30/2010 02:45 amHere is something to chew on, Making a few assumptions about TAN,, the same thrust as the the stage and a half plus sustainer could be produced with just the sustainer in about the same mass as the sustainer.Pure fantasy, but still interesting.Do not forget, the Atlas also placed itself with the much heavier mercury capsule in orbit.With balloon tanks and a modern TAN-like engine, I think you could do SSTO, possibly with enough margin to make it fully reusable. A modern TAN engine, done right could have much better vacuum performance than the Atlas sustainer, without having to carry the mass of the booster engines even for the first bit of the flight.~JonSounds great going up.. not sure how you get it back down? Balloon tanks and heat dissipation/shielding on re-entry.. hmm.. what are your thoughts there Jon? How much mass would you chew up to make it reusable?
Quote from: DiggyCoxwell on 04/30/2010 02:26 am nor were there lightweight titanium rocketmotors (The 1958 Atlas had special steel alloy or stainless steel rocket motors; heavy by today's standards).Nor are they any now.
Here's one way to design a SSTO vehicle that I believe will work. Build a long cylindrical tank with a common bulkhead. Add wings, thermal protection and six SSME sized engines at the base using 2130 t of LOX/RP-1 (and definitely not LOX/LH2). Add the payload to the side, light the candle and in about seven minutes you will have put a 34.8 t payload into an 80x185 km orbit. Vehicle dry mass is 139.5 t. The payload does a small burn at apogee to go into orbit. The vehicle performs a once-around maneuver, returning to the launch site after about 90 minutes. Using more exotic RP-X2 (quadracyclene) fuel increases payload mass by 67.5% to 58.3 t. Here's a paper I wrote about it.
Quote from: Jim on 04/30/2010 02:47 amQuote from: DiggyCoxwell on 04/30/2010 02:26 am nor were there lightweight titanium rocketmotors (The 1958 Atlas had special steel alloy or stainless steel rocket motors; heavy by today's standards).Nor are they any now. Then I chose the right webpage category: "Advanced Concepts";at least advanced concepts involving titanium metallurgy, and titaniummachining (Yes, I am aware that titanium is a difficult metal to machine.)
Quote from: DiggyCoxwell on 04/30/2010 05:33 pmQuote from: Jim on 04/30/2010 02:47 amQuote from: DiggyCoxwell on 04/30/2010 02:26 am nor were there lightweight titanium rocketmotors (The 1958 Atlas had special steel alloy or stainless steel rocket motors; heavy by today's standards).Nor are they any now. Then I chose the right webpage category: "Advanced Concepts";at least advanced concepts involving titanium metallurgy, and titaniummachining (Yes, I am aware that titanium is a difficult metal to machine.)The point is more that existing engines are not substantially lighter weight than the LR89 used on the Atlas D. It had a T/W ratio of 120, compared to about 100 for the RS-27, which was a much more recent kerosene engine (of similar thrust rating). Even the venerable NK-33 only managed 135. So "heavy by today's standards" is an unfounded, and in fact false, statement
Quote from: Steven Pietrobon on 04/30/2010 06:35 amHere's one way to design a SSTO vehicle that I believe will work. Build a long cylindrical tank with a common bulkhead. Add wings, thermal protection and six SSME sized engines at the base using 2130 t of LOX/RP-1 (and definitely not LOX/LH2). Add the payload to the side, light the candle and in about seven minutes you will have put a 34.8 t payload into an 80x185 km orbit. Vehicle dry mass is 139.5 t. The payload does a small burn at apogee to go into orbit. The vehicle performs a once-around maneuver, returning to the launch site after about 90 minutes. Using more exotic RP-X2 (quadracyclene) fuel increases payload mass by 67.5% to 58.3 t. Here's a paper I wrote about it.2130 + 139.5 + 34.8 = 2304.3139.5 + 34.8 = 174.3mass ratio 2304.3/174.3 is 13.2 2.58 x Ve =9 or Ve is 3.4 km/sec or ISP of 360 secondsThe F1A engine was 265 seconds. What engine are you proposing?Structure fraction 139.5/2304.3 is 6.05%You seem to be thinking about reusable since you mention it coming back to the launch pad in 90 minutes.I am not a rocket engineer, just an EE with an interest. But I have asked Gary Hudson whose opinion is that the structure fraction for reusable needs to be 15% or more.That's about the structure fraction of a Skylon.How do you get it to 6%?Best wishes,Keith Henson
Single-Stage To Orbit still appears out of reachto many engineers, with the exception of the hypotheticalHOTOL/Skylon concepts.<snip>What do you think?