Prochron 0811B will be set aside at this point. The OTRAG style configuration appears to be the way to go, but it is obviously rather limited. The propulsion for Prochron and Symtex is likely to be oxykerosene blowdown pressure-fed made of ordinary steel, perhaps with some cheap hoop wrapped composite. The selection of first stage motor is still Cesaroni M4770-P V-max...this one lasts only two seconds. Everything else is open, but the assumption for the stage is that it is 10% of its full mass at burnout. The module turned out to be 151kg, sized to optimize version 3204. The ascent is 9500m/s. The numbering system works like this:
1st digit: number of modules in Stage Two
2nd digit: number of modules in Stage Three
3rd and 4th digits: 10kg units of Stage Four
Version 1000: The sounding rocket (has 4 modules in Stage One)
Total impulse is 445860Ns, lower S class and about half of the maximum allowable under FAA amateur rocketry rules. It has to carry a payload of at least 100kg in order to stay under the amateur ceiling.
Version 3104: Design point, 3kg orbital booster (10kg listed payload allows 7kg for guidance and dunnage; 4kg has been allowed for the fairing.) Gross mass is 724kg. Has 10 Stage One motors.
Version 2104: Minimal: barely makes orbit with its guidance system (700g of payload). Gross mass is 557.5kg. Has 8 Stage One motors.
Version 4104: Payload of 5kg, Gross mass is 890.2kg, has 12 Stage One motors.
Version 5204: Payload of 9.8kg, Gross mass is 1230kg, has 17 Stage One motors.
Version 6204: Payload of 11.8kg, Gross mass is 1402.8kg, has 20 Stage One motors.
Version 6210: The biggest. Payload of 13.8kg. Gross mass is 1464.8kg. Has a bigger upper stage.
Post comment or send email if you want access to the spreadsheet. I need to know your email, post like "aftercolumbia at gmail dot com" to make sure it doesn't get filtered by blogger software. Oh yeah, that's my email address if you'd rather not have any exposure in the comments section. Check out the landers shortly to be posted at http://www.openluna.org
Terry
Friday, November 28, 2008
Saturday, November 22, 2008
Prochron 0811B
It's official: Prochron 0811B specs
Booster on pad: RTL fuelled: 695kg
Booster on pad: RTL unfuelled: 141kg (Stage One installed)
Booster on truck: not fuelled: 75kg (Stage One not installed)
Stage One: Cesaroni M4770-P http://www.pro38.com/motor/M4770-P.html 6.6kg total per module; ten modules
Stage Two: Prochron module * 3
Stage Three: Prochron module *1
Stage Four: Prochron upper stage
Cesaroni M4770-P: 6.6kg rocket stage, 3.1kg at burnout, 2043m/s exhaust speed. Stages at 107m/s elapsed serial delta-v after 2.0sec. Average thrust: 4770N (47.7kN vehicle)
Prochron module: 150kg loaded, 15kg empty. Average exhaust speed 2400m/s first stage, 3000m/s further stages. Estimated 20cm diameter, 5m long (avg. density 0.75kg/L). Average thrust: 2500N (tentative; 7500N Stage Two.) Estimated burn time: 162sec (assumed constant thrust)
Prochron Upper stage: 20kg loaded, 6kg empty. Average exhaust speed 3000m/s. Estimated 20cm in diameter, 0.6m long. Average thrust: 250N Estimated burn time: 168sec (assumed constant thrust)
Fairing: 4kg, payload 5kg (i.e.: 3kg Cubesat plus 2kg deployer)
Accomplishments:
1. 3:1 Stage Two: Stage Three found optimal, needs to be verified with better optimizer
2. 6m launch tower estimated exit speed at 27m/s based on http://www.thrustcurve.org/motorguide.jsp?rocket=400
Objections:
1. Calculated Delta-v only 9258m/s due to previously undetected error in optimizer. Would have to be air launched.
2. Module burn times are too long. Try to get them under 120sec. A cost/practical requirement of the Prochron is to achieve orbit before crossing the launch site horizon.
3. Amateur/Sounding version compatibility is not known.
4. Full fledged solids in 1st stage vs. preferred hybrids. Solids are kit reloadable and made in Canada (the plus side.)
5. Does this preliminary study leave enough room for recovery systems?
Booster on pad: RTL fuelled: 695kg
Booster on pad: RTL unfuelled: 141kg (Stage One installed)
Booster on truck: not fuelled: 75kg (Stage One not installed)
Stage One: Cesaroni M4770-P http://www.pro38.com/motor/M4770-P.html 6.6kg total per module; ten modules
Stage Two: Prochron module * 3
Stage Three: Prochron module *1
Stage Four: Prochron upper stage
Cesaroni M4770-P: 6.6kg rocket stage, 3.1kg at burnout, 2043m/s exhaust speed. Stages at 107m/s elapsed serial delta-v after 2.0sec. Average thrust: 4770N (47.7kN vehicle)
Prochron module: 150kg loaded, 15kg empty. Average exhaust speed 2400m/s first stage, 3000m/s further stages. Estimated 20cm diameter, 5m long (avg. density 0.75kg/L). Average thrust: 2500N (tentative; 7500N Stage Two.) Estimated burn time: 162sec (assumed constant thrust)
Prochron Upper stage: 20kg loaded, 6kg empty. Average exhaust speed 3000m/s. Estimated 20cm in diameter, 0.6m long. Average thrust: 250N Estimated burn time: 168sec (assumed constant thrust)
Fairing: 4kg, payload 5kg (i.e.: 3kg Cubesat plus 2kg deployer)
Accomplishments:
1. 3:1 Stage Two: Stage Three found optimal, needs to be verified with better optimizer
2. 6m launch tower estimated exit speed at 27m/s based on http://www.thrustcurve.org/motorguide.jsp?rocket=400
Objections:
1. Calculated Delta-v only 9258m/s due to previously undetected error in optimizer. Would have to be air launched.
2. Module burn times are too long. Try to get them under 120sec. A cost/practical requirement of the Prochron is to achieve orbit before crossing the launch site horizon.
3. Amateur/Sounding version compatibility is not known.
4. Full fledged solids in 1st stage vs. preferred hybrids. Solids are kit reloadable and made in Canada (the plus side.)
5. Does this preliminary study leave enough room for recovery systems?
Sunday, November 16, 2008
Total Thrust Pressure: Why the Big Dumb Booster Must Graduate High School
Total thrust pressure is the sum of momentum thrust pressure and exit pressure in a rocket motor. Confused yet? Well, it's rocket science. Skip to the bottom line: with only a few exceptions, the deciding dimension of the size of a liquid fuelled rocket motor is the diameter of the nozzle exit. It has to fit in under your booster, and it has to generate a certain amount of thrust to lift your booster off the ground, sea, or preceding stage of flight. As a booster designer, you also want fuel efficiency. Above all, you want a cheap ride to orbit (or else you probably wouldn't bother reading any of this.)
You want fuel efficiency? You therefore want a high expansion nozzle. The higher the expansion ratio, the more efficient the nozzle is at high altitude. There are two problems:
- On Earth's surface, atmospheric pressure tries to keep your rocket exhaust from expanding out of the nozzle. The worst case scenario is that your rocket exhaust quits expanding before it actually leaves the nozzle, separating from the walls and leaving part of the nozzle unused. This is especially annoying in a crosswind, which can cause your exhaust to separate only on one side of the nozzle (and this might happen anyway). This normally happens when a motor is first started, and is why most large boosters are bolted down until the engines are up and running.
- In the vacuum, it would be nice to have an infinite expansion ratio, but you will never have enough room in your design to do this. You therefore have to decide on an expansion ratio that will fit in your booster while also providing enough thrust. The length of the nozzle, and the skirt or truss around it to allow the stage to be carried by the booster's first stage, is generally the deciding factor, but can be mitigated in three ways. The Russians like multi-motor engines (look up the RD-0110 and RD-0124 for examples), but because not all of the base area is nozzle area, the required thrust pressure increases by at least 45.7% (assuming four motors instead of one.) The Americans like extendable nozzles (look up RL-10B-2), which slide the the bottom part of the nozzle up around the top part, much like a plastic lightsaber toy. Many providers (look up Transtage and Breeze-M) like to use donut shaped tanks (technical word is "toroidal") so that they can snuggle the upper, narrow portion of the motor up inside it. You can also see this in certain solid motors (look up Star 10).
As it relates to "big dumb boosters", I'll deal with the first stage only. As a cheap booster designer, you'll be willing to spend about the same amount of money on the first stage as the second stage, and the second stage will be smaller, and therefore somewhat more sophisticated (unless your first stage is much more reusable than your second stage, since the cost per flight is what really matters.)
I did a quick and dirty study on the effects of total thrust pressure scaling all by itself. I picked the typical parameters of a dumb booster that burns oxykerosene fuel at a mixture ratio of 2.5:1, is seven times as long as it is in diameter, uses common bulkhead propellant tanks and miraculous zero-length interstages (resulting from the desire for a quick study, not as a realistic consideration...this is why most launch vehicles, even ones matched to considerably narrower lines than their actual diameters, are considerably longer than 7 diameters...that and the fact that many of them use oxyhydrogen upper stages, which has a much lower average density.) Finally, its burnout mass is 10% of its full mass, and its payload mass is 1.5% of its liftoff mass. It lifts off with an accelleration of 12m/s2 (2.19m/s2 more than gravity, peppy for a big orbital booster, but dangerously pitiful for a model rocket.) After running it through a series of simple geometric formulae (such things as area = pi*radius squared and pressure = force/area), I came up with the following general rules about how the required total thrust pressure would scale using these assumptions:
Booster mass = 7.39 diameters cubed (diameter in m, mass in kg)
Payload mass = 0.348 diameters cubed (diameter in m, mass in kg)
Total thrust pressure required = 88.6 diameters (diameter in m, pressure in kPa)
0.1m (4 inches) diameter: 7.29kg total mass; 348g orbital payload. Requires 8.86kPa
0.2m (8 inches) diameter: 58.3kg total mass; 2.78kg orbital payload. Requires 17.72kPa
0.3m (12 inches) diameter: 197kg total mass; 9.40kg orbital payload. Requires 26.88kPa
As orbital concepts, these above are pretty fanciful. The closest real rockets are high power model rockets. They require about four times as much liftoff accelleration for safe operation, and therefore four times as much thrust pressure. Even the biggest, needing 108kPa, is fairly easy to meet.
New: 19 November 2008: Previously ignored OTRAG CRPU stage evaluated. The OTRAG system sought to achieve low cost orbital access buy building up multistage boosters from small common modules. Details at http://www.astronautix.com/lvs/otrag.htm. The CPRU has a loaded mass of 1500kg, diameter of 0.27m, thrust of 25kN at sea level and a length of 16m (producing a fineness ratio of ). The total thrust pressure achieved is 145.0kPa.
The vehicle failed primarily because of politics before orbit could be reached. It was being built in West Germany, and its neighbours were skittish about its potential use as a missile. This wasn't helped by the use of a Libyan test site and the theft of some CPRU hardware by the Libyans in 1983. Prime Aero (my shorthand for Boeing, Lockheed Martin, Orbital Sciences and their predecessors in the US) saw the OTRAG as a market threat. I've noticed throughout my study of history that when something happens to threaten the US military/industrial complex or energy industry, "conspiracy deception" happens. OTRAG was accused of being a cover for a joint German/South African nuclear cruise missile, and so appears to have fallen victim to this phenomenon. The primer on conspiracy deception is Nick Cook's The Hunt For Zero Point
(http://www.amazon.com/Hunt-Zero-Point-Classified-Antigravity/dp/0767906284/ref=sr_1_1?ie=UTF8&s=books&qid=1227117270&sr=8-1)
Technically, OTRAG probably would have made orbit with only small payloads, but I'm sure, had it the chance, the company would probably have expanded to an Ascent Roadmap-like family. The CPRU, when clustered square, produces a 99.5kPa total thrust pressure, suggesting an orbital payload limit in the ballpark of 500kg.
Old Again:
0.5m (20 inches) diameter: 911kg total mass; 43.5kg orbital payload. Requires 44.3kPa
0.8m (31 inches) diameter: 3.73 tonnes total mass; 178kg orbital payload. Requires 70.9kPa
1.0m (39 inches) diameter: 7.29 tonnes total mass; 348kg orbital payload. Requires 88.6kPa
1.2m (47 inches) diameter: 12.6 tonnes total mass; 601kg orbital payload. Requires 106.3kPa
This one best matches the Orbital Pegasus booster, the one that is air dropped. It starts out at about 20m/s2, solid thrust, and masses about twice as much as this. Also, a diameter of 50in. It's actual total thrust pressure is 384kPa, hinting at an unnecessarily smart booster.
1.5m (59 inches) diameter: 24.6 tonnes total mass; 1175kg orbital payload. Requires 132.9kPa
1.8m (71 inches) diameter: 42.5 tonnes total mass; 2030kg orbital payload. Requires 159.5kPa
2.0m (79 inches) diameter: 85.3 tonnes total mass; 2785kg orbital payload. Requires 177.2kPa
The actual diameter of Taurus at 73 tonnes/1380kg payload is 2.36m. It's actual total thrust pressure is 315.5kPa, again hinting at an unncecessarily smart booster. Pegasus and Taurus are solid propellant with very high pressures, resulting in heavy stages and high drag. This is why their payload proportions are smaller. They're not "smart" in the same way as conventional boosters.
2.5m (98 inches) diameter: 117 tonnes total mass; 5438kg orbital payload. Requires 221.5kPa
This line pegs the Delta II very closely. Payload, diameter (base diameter is about 4m with the strap-ons, core diameter is 2.4m) and lift off mass are surprisingly close. Delta II also happens to be the best from a $/kg to orbit perspective in LEO On The Cheap (go to http://www.dunnspace.com/ to download this excellent Air Force University Press book by John R. London III.)
3.0m (118 inches) diameter: 197 tonnes total mass; 6396kg orbital payload. Requires 268.8kPa
This line is probably the limit of practical pressure-fed boosters. It is difficult to exceed 300kPa by much with pressure-fed liquid fuelled motors. With the fancy features to do so (Tridyne pressurization, composite wound tanks), turbopumps become competitive with the better educated dumb boosters. This opinion is based on a few pages of ASME B&PV Code Sec VIII/1 calculations to estimate tank mass proportions at various pressures and a few thousand pages of AFAL Isp Calculator output (also at http://www.dunnspace.com/) and the fact that conventional booster's $/kg payload cost bottoms out right here.
3.5m (138 inches) diameter: 313 tonnes total; 14.9 tonne orbital payload. Requires 310.1kPa
This line pegs the Atlas V non-strapped configurations almost perfectly, except that the payloads are smaller, at about 8 tonnes (and the actual core diameter is 3.81m.) This is probably a side-effect of the two motor arrangement, which is the least efficient way to pack multiple motors under the base of a booster (note: the Atlas V uses and RD-180 engine, which has two RD-190 class motors ganged to a single set of turbopumps. The RD-190 engine (used in Angara) has one such motor, while the RD-170 (Energia strap-on) and RD-171 (Zenit...real name for Sea Launch and Land Launch) have four such motors. American ganged engines include the MA-5 Boost (Atlas to version IIAS) and LR-91 (Titan II, III, and IV core stages). This line also pegs the Soyuz, which is an interesting study in total thrust pressure economics. The gracefully tapered shape of the Soyuz booster results from the relatively low total trust pressure of the four motor ganged engines used in the first and second stages (RD-107 used in the first stage, that is, the strap-ons and the very similar RD-108 engine used in the core second stage.)
4.0m (157 inches) diameter: 467 tonnes total; 22.3 tonnes orbital payload. Requires 354.4kPa
Here we have just passed the largest operational solid rocket motor: the RSRM. Translation for rocketry noobs: the Shuttle strap-on booster, the one that blew up the teacher in 1986. This line pegs almost every booster in the payload class: Ares I, Atlas V, Zenit, Proton, and Ariane 5. Ascent Roadmap's Lilmax is also looking for real estate on this line.
4.5m (177 inches) diameter: 664 tonnes total; 31.7 tonnes orbital payload. Requires 398.7kPa
5.0m (197 inches) diameter: 911 tonnes total; 43.5 tonnes orbital payload. Requires 443.0kPa
6.0m (236 inches) diameter: 1575 tonne total; 75.2 tonnes orbital payload. Requires 531.6kPa
An astute rocket fan will notice that both the total mass, payload mass have passed that of the 6.5m diameter Saturn IB (590 tonnes, 18.6 tonnes orbital payload). Ouchy, no? Actually, the Soyuz is about that diameter across its base. This shows that a wide tapered or squat launch vehicle is another approach to low cost space access by keeping the total thrust pressure requirement down.
7.0 m (276 inches) diameter: 2500 tonnes total, 119.4 tonnes orbital. Requires 620.2kPa
8.0 m (315 inches) diameter: 3732 tonnes total, 178.2 tonnes orbital. Requires 708.8kPa
There would be few matches past this point because the thrust pressure requirements are getting too high for any economical vehicle to match them. For example, the Saturn V (<140 tonnes orbital, 2800 tonnes total, 10.1m diameter) matches the ~7.2m line except for diameter, which lowers the total thrust pressure requirement by about 29% to 440kPa. Saturn V's actual total thrust pressure is 425kPa...pretty close for a quick and dirty study.
9.0 m (354 inches) diameter: 5314 tonnes total, 254 tonnes orbital. Requires 797.4kPa
This is Freezerburn's core diameter. It has no hope of meeting that total thrust pressure with clustered Lilmax modules. The result is that it will have a lot more base real estate than this quick and dirty study thinks such a vehicle should have, following the trend of many successful conventional boosters.
10.0m (394 inches) diameter: 7290 tonnes total, 348 tonnes orbital. Requires 886kPa
And that's as far as my quick and dirty total thrust pressure study went. It is clear that booster designers will have to take the best that today's technology can offer (staged combustion, 20+MPa chamber pressures, composite construction, preheated pressurization systems, etc.) and arrange them very creatively to launch 350 tonne payloads economically. These payloads will be asking for diameters of 10.0m or even more...we can expect their boosters to be even wider at ground level!!
You want fuel efficiency? You therefore want a high expansion nozzle. The higher the expansion ratio, the more efficient the nozzle is at high altitude. There are two problems:
- On Earth's surface, atmospheric pressure tries to keep your rocket exhaust from expanding out of the nozzle. The worst case scenario is that your rocket exhaust quits expanding before it actually leaves the nozzle, separating from the walls and leaving part of the nozzle unused. This is especially annoying in a crosswind, which can cause your exhaust to separate only on one side of the nozzle (and this might happen anyway). This normally happens when a motor is first started, and is why most large boosters are bolted down until the engines are up and running.
- In the vacuum, it would be nice to have an infinite expansion ratio, but you will never have enough room in your design to do this. You therefore have to decide on an expansion ratio that will fit in your booster while also providing enough thrust. The length of the nozzle, and the skirt or truss around it to allow the stage to be carried by the booster's first stage, is generally the deciding factor, but can be mitigated in three ways. The Russians like multi-motor engines (look up the RD-0110 and RD-0124 for examples), but because not all of the base area is nozzle area, the required thrust pressure increases by at least 45.7% (assuming four motors instead of one.) The Americans like extendable nozzles (look up RL-10B-2), which slide the the bottom part of the nozzle up around the top part, much like a plastic lightsaber toy. Many providers (look up Transtage and Breeze-M) like to use donut shaped tanks (technical word is "toroidal") so that they can snuggle the upper, narrow portion of the motor up inside it. You can also see this in certain solid motors (look up Star 10).
As it relates to "big dumb boosters", I'll deal with the first stage only. As a cheap booster designer, you'll be willing to spend about the same amount of money on the first stage as the second stage, and the second stage will be smaller, and therefore somewhat more sophisticated (unless your first stage is much more reusable than your second stage, since the cost per flight is what really matters.)
I did a quick and dirty study on the effects of total thrust pressure scaling all by itself. I picked the typical parameters of a dumb booster that burns oxykerosene fuel at a mixture ratio of 2.5:1, is seven times as long as it is in diameter, uses common bulkhead propellant tanks and miraculous zero-length interstages (resulting from the desire for a quick study, not as a realistic consideration...this is why most launch vehicles, even ones matched to considerably narrower lines than their actual diameters, are considerably longer than 7 diameters...that and the fact that many of them use oxyhydrogen upper stages, which has a much lower average density.) Finally, its burnout mass is 10% of its full mass, and its payload mass is 1.5% of its liftoff mass. It lifts off with an accelleration of 12m/s2 (2.19m/s2 more than gravity, peppy for a big orbital booster, but dangerously pitiful for a model rocket.) After running it through a series of simple geometric formulae (such things as area = pi*radius squared and pressure = force/area), I came up with the following general rules about how the required total thrust pressure would scale using these assumptions:
Booster mass = 7.39 diameters cubed (diameter in m, mass in kg)
Payload mass = 0.348 diameters cubed (diameter in m, mass in kg)
Total thrust pressure required = 88.6 diameters (diameter in m, pressure in kPa)
0.1m (4 inches) diameter: 7.29kg total mass; 348g orbital payload. Requires 8.86kPa
0.2m (8 inches) diameter: 58.3kg total mass; 2.78kg orbital payload. Requires 17.72kPa
0.3m (12 inches) diameter: 197kg total mass; 9.40kg orbital payload. Requires 26.88kPa
As orbital concepts, these above are pretty fanciful. The closest real rockets are high power model rockets. They require about four times as much liftoff accelleration for safe operation, and therefore four times as much thrust pressure. Even the biggest, needing 108kPa, is fairly easy to meet.
New: 19 November 2008: Previously ignored OTRAG CRPU stage evaluated. The OTRAG system sought to achieve low cost orbital access buy building up multistage boosters from small common modules. Details at http://www.astronautix.com/lvs/otrag.htm. The CPRU has a loaded mass of 1500kg, diameter of 0.27m, thrust of 25kN at sea level and a length of 16m (producing a fineness ratio of ). The total thrust pressure achieved is 145.0kPa.
The vehicle failed primarily because of politics before orbit could be reached. It was being built in West Germany, and its neighbours were skittish about its potential use as a missile. This wasn't helped by the use of a Libyan test site and the theft of some CPRU hardware by the Libyans in 1983. Prime Aero (my shorthand for Boeing, Lockheed Martin, Orbital Sciences and their predecessors in the US) saw the OTRAG as a market threat. I've noticed throughout my study of history that when something happens to threaten the US military/industrial complex or energy industry, "conspiracy deception" happens. OTRAG was accused of being a cover for a joint German/South African nuclear cruise missile, and so appears to have fallen victim to this phenomenon. The primer on conspiracy deception is Nick Cook's The Hunt For Zero Point
(http://www.amazon.com/Hunt-Zero-Point-Classified-Antigravity/dp/0767906284/ref=sr_1_1?ie=UTF8&s=books&qid=1227117270&sr=8-1)
Technically, OTRAG probably would have made orbit with only small payloads, but I'm sure, had it the chance, the company would probably have expanded to an Ascent Roadmap-like family. The CPRU, when clustered square, produces a 99.5kPa total thrust pressure, suggesting an orbital payload limit in the ballpark of 500kg.
Old Again:
0.5m (20 inches) diameter: 911kg total mass; 43.5kg orbital payload. Requires 44.3kPa
0.8m (31 inches) diameter: 3.73 tonnes total mass; 178kg orbital payload. Requires 70.9kPa
1.0m (39 inches) diameter: 7.29 tonnes total mass; 348kg orbital payload. Requires 88.6kPa
1.2m (47 inches) diameter: 12.6 tonnes total mass; 601kg orbital payload. Requires 106.3kPa
This one best matches the Orbital Pegasus booster, the one that is air dropped. It starts out at about 20m/s2, solid thrust, and masses about twice as much as this. Also, a diameter of 50in. It's actual total thrust pressure is 384kPa, hinting at an unnecessarily smart booster.
1.5m (59 inches) diameter: 24.6 tonnes total mass; 1175kg orbital payload. Requires 132.9kPa
1.8m (71 inches) diameter: 42.5 tonnes total mass; 2030kg orbital payload. Requires 159.5kPa
2.0m (79 inches) diameter: 85.3 tonnes total mass; 2785kg orbital payload. Requires 177.2kPa
The actual diameter of Taurus at 73 tonnes/1380kg payload is 2.36m. It's actual total thrust pressure is 315.5kPa, again hinting at an unncecessarily smart booster. Pegasus and Taurus are solid propellant with very high pressures, resulting in heavy stages and high drag. This is why their payload proportions are smaller. They're not "smart" in the same way as conventional boosters.
2.5m (98 inches) diameter: 117 tonnes total mass; 5438kg orbital payload. Requires 221.5kPa
This line pegs the Delta II very closely. Payload, diameter (base diameter is about 4m with the strap-ons, core diameter is 2.4m) and lift off mass are surprisingly close. Delta II also happens to be the best from a $/kg to orbit perspective in LEO On The Cheap (go to http://www.dunnspace.com/ to download this excellent Air Force University Press book by John R. London III.)
3.0m (118 inches) diameter: 197 tonnes total mass; 6396kg orbital payload. Requires 268.8kPa
This line is probably the limit of practical pressure-fed boosters. It is difficult to exceed 300kPa by much with pressure-fed liquid fuelled motors. With the fancy features to do so (Tridyne pressurization, composite wound tanks), turbopumps become competitive with the better educated dumb boosters. This opinion is based on a few pages of ASME B&PV Code Sec VIII/1 calculations to estimate tank mass proportions at various pressures and a few thousand pages of AFAL Isp Calculator output (also at http://www.dunnspace.com/) and the fact that conventional booster's $/kg payload cost bottoms out right here.
3.5m (138 inches) diameter: 313 tonnes total; 14.9 tonne orbital payload. Requires 310.1kPa
This line pegs the Atlas V non-strapped configurations almost perfectly, except that the payloads are smaller, at about 8 tonnes (and the actual core diameter is 3.81m.) This is probably a side-effect of the two motor arrangement, which is the least efficient way to pack multiple motors under the base of a booster (note: the Atlas V uses and RD-180 engine, which has two RD-190 class motors ganged to a single set of turbopumps. The RD-190 engine (used in Angara) has one such motor, while the RD-170 (Energia strap-on) and RD-171 (Zenit...real name for Sea Launch and Land Launch) have four such motors. American ganged engines include the MA-5 Boost (Atlas to version IIAS) and LR-91 (Titan II, III, and IV core stages). This line also pegs the Soyuz, which is an interesting study in total thrust pressure economics. The gracefully tapered shape of the Soyuz booster results from the relatively low total trust pressure of the four motor ganged engines used in the first and second stages (RD-107 used in the first stage, that is, the strap-ons and the very similar RD-108 engine used in the core second stage.)
4.0m (157 inches) diameter: 467 tonnes total; 22.3 tonnes orbital payload. Requires 354.4kPa
Here we have just passed the largest operational solid rocket motor: the RSRM. Translation for rocketry noobs: the Shuttle strap-on booster, the one that blew up the teacher in 1986. This line pegs almost every booster in the payload class: Ares I, Atlas V, Zenit, Proton, and Ariane 5. Ascent Roadmap's Lilmax is also looking for real estate on this line.
4.5m (177 inches) diameter: 664 tonnes total; 31.7 tonnes orbital payload. Requires 398.7kPa
5.0m (197 inches) diameter: 911 tonnes total; 43.5 tonnes orbital payload. Requires 443.0kPa
6.0m (236 inches) diameter: 1575 tonne total; 75.2 tonnes orbital payload. Requires 531.6kPa
An astute rocket fan will notice that both the total mass, payload mass have passed that of the 6.5m diameter Saturn IB (590 tonnes, 18.6 tonnes orbital payload). Ouchy, no? Actually, the Soyuz is about that diameter across its base. This shows that a wide tapered or squat launch vehicle is another approach to low cost space access by keeping the total thrust pressure requirement down.
7.0 m (276 inches) diameter: 2500 tonnes total, 119.4 tonnes orbital. Requires 620.2kPa
8.0 m (315 inches) diameter: 3732 tonnes total, 178.2 tonnes orbital. Requires 708.8kPa
There would be few matches past this point because the thrust pressure requirements are getting too high for any economical vehicle to match them. For example, the Saturn V (<140 tonnes orbital, 2800 tonnes total, 10.1m diameter) matches the ~7.2m line except for diameter, which lowers the total thrust pressure requirement by about 29% to 440kPa. Saturn V's actual total thrust pressure is 425kPa...pretty close for a quick and dirty study.
9.0 m (354 inches) diameter: 5314 tonnes total, 254 tonnes orbital. Requires 797.4kPa
This is Freezerburn's core diameter. It has no hope of meeting that total thrust pressure with clustered Lilmax modules. The result is that it will have a lot more base real estate than this quick and dirty study thinks such a vehicle should have, following the trend of many successful conventional boosters.
10.0m (394 inches) diameter: 7290 tonnes total, 348 tonnes orbital. Requires 886kPa
And that's as far as my quick and dirty total thrust pressure study went. It is clear that booster designers will have to take the best that today's technology can offer (staged combustion, 20+MPa chamber pressures, composite construction, preheated pressurization systems, etc.) and arrange them very creatively to launch 350 tonne payloads economically. These payloads will be asking for diameters of 10.0m or even more...we can expect their boosters to be even wider at ground level!!
Saturday, November 15, 2008
Introduction to The Ascent Roadmap
The Ascent Roadmap is a product of the After Columbia Project (http://aftercolumbia.tripod.com/ and http://aftercolumbiamars.blogspot.com/). It is intended to chart the most economical booster concepts for each class of payload
The Ascent Roadmap is also a significant part of the OpenLuna Wiki (which will eventually begin to concentrate on the Lunar Access Plan.) The following is from memory, and should be very similar in jist to what you will find at http://www.openluna.org/wiki/index.php/Ascent_Roadmap but not verbatim.
First, I highly recommend the book by John R. London III, LEO On The Cheap hosted at http://www.dunnspace.com/. It has only one glitch, as does almost all advocates of Minimum Cost Design (MCD) boosters: it has underestimated the scaling problem of total thrust pressure, which makes it very difficult to design large pressure-fed boosters with payloads above 20 tonnes to Low Energy Orbit.
Payload Class Boosters:
Prochron: 3kg to Low Earth Orbit.
Earth-to-Orbit Centerpiece of: Hobby Access Plan (status=stub)
Stage One: off the shelf high power rocket motors of N impulse class. These motors provide the initial thrust to lift the booster out of the launch tower and give it enough speed so that it's passively stable design has enough speed to avoid excessive weathervaning. They are jettisoned after six seconds, and are recovered the same way as high power rockets are always (sic) recovered: parachute and puppy dog.
Stage Two (ver. 0811A): A core stage with fins, a single motor, oxyfuel (probably oxypropane) propellant combination. Additional stages, if applicable, are stacked on top. The entire assembled vehicle fits under a total impulse class of T, allowing it to be operated as an amateur rocket...as long as it stays under 150km peak altitude.
Stage Two (ver. 0811B): 3 common modules, the sort inspired by OTRAG, strapped to a core stage. Each module is a blowdown single motor stage (probably oxypropane). This means that Prochron amateur rockets could use this module, and possibly be far smaller than ver. 0811A.
Stage Three (ver. 0811A): a single common diameter stage stacked on top of the second stage core, with a small pressure-fed oxyfuel motor, smaller than that in Stage Two.
Stage Three (ver. 0811B): The single module in between the Stage Two modules, carrier of Stage Four (if applicable)
Stage Four: a small upper stage designed to apply a precise impulse bit to the payload to get it into the proper orbit and correct for errors in earlier stages. It carries a small cold gas RCS system.
Operation: Prochron flies passively (or semi-passively) through Stages One and Two, which operate in the atmosphere. Stages Three and Four require active guidance and stabilization to correct from Stages One and Two, and because without air, fins don't work. The fairing is jettisoned during Stage Three. The payload is based on CalPoly's Cubesat (http://www.cubesat.org/). 3kg forms a single "pod" of CubeSats.
Symtex: Up to 500kg to orbit
Earth-to-Orbit Centerpiece of: nothing so far
A modular pressure-fed launch vehicle intended to fill the niche underneath the Orbital Sciences Pegasus and Minotaur class boosters. If it entered service as a commercial launch vehicle, it would have no competition, except for the very largest configuration, which nearly matches Pegasus/Minotaur performance.
Common Motor: a single oxyfuel (probably oxypropane, possibly same as Prochron Stage Two ver. 0811A) used by all stages except for the upper stage, which mounts a smaller Space Motor (probably same as Prochron Stage Three).
Strap-on Module: Wide enough only to mount one Common Motor, this small module provides high lift-off thrust for about 40 seconds.
Core Modules: Mounts any number of motors from one to four (including the possibility of a single high expansion version for a second stage.) They will probably be cut to two different lengths. Try not to think of them as putty-like: stretching and cutting stages is not so simple.
Upper Stage: Contains the guidance system, is multiple maneuver capable, and contains the payload interface and vehicle electrical sources. A special type of internal gear expander coupled pump (think "displacement turbopump") is being considered. It is based on the StarRotor design (http://www.starrotor.com/), and StarRotor Corporation has been queried for its potential use. Special thanks to them for providing After Columbia Project with basic application formulae and the University of Idaho ALLPROPS software.
Operation: Symtex is actively guided all the way to orbit, but it is intended that it be passively stable until at least the first staging event. It therefore does not require a tower or rail for weathervaning control. For conventional launch vehicles, typically extensive balloons and often patrol aircraft are used to measure winds aloft. To avoid the expense, Symtex will provide extra margin for corrections, and extra thrust to get out of the atmosphere quickly, and thus mitigate the performance effects of wind shear. The smallest configurations use strap-configured core stages, who's core operates primarily as a second stage. The largest configurations will probably use Long Cores strapped by Short Cores, plus a final Short Core as a second stage. The upper stage will probably be used in such configurations for circularization maneuvers.
Kilder: 1000 to 8000kg Low Energy Orbit
Earth-to-Orbit Centerpiece of: Lunar Access Plan
Kilder features an pressure-fed oxyfuel (probably oxykerosene) core which must be strapped in order to rise from the pad. The strap-on system provides the first stage, and a squat, rotorpump engined (probably oxyethylene) upper stage comprises the third stage. The most advanced of the strap-on systems carry Lilmax turbopump engines, once that engine has been developed for Lilmax.
Lilmax: 15 to 50 tonnes Low Energy Orbit
Earth-to-Orbit Centerpiece of: Mars Access Plan
Lilmax begins to approach the size and complexity of typical boosters in terms of its systems and launch configurations, even though it is made of spun/rolled steel. Compared to extant boosters, it considers some very unusual features for its lower stage module, along with a more conventional upper stage. The modules come in a single length, without stretching or cutting down, however the upper stage will probably have two different sizes to accomodate different payload levels and final orbits. Unusual features (unusual both to "big dumb boosters" and conventional launch vehicles) are:
- Segmented tank construction: This allows rail and truck transportability of individual segments, which form a much larger stage when assembled. This is currently done with the Shuttle's solid boosters.
- Crossfeeding of propellants from strap-ons to core, allowing the core to remain full until the strap-ons burn out and are jettisoned.
- Pressure-stabilized structure. The normal tank pressure is 200psig with a burst factor of safety of 2.0, so it may be able to stand on its own anyway. If it can't, we'd rather use cradles and removable internal webs during transport than add stiffeners to the design. Most boosters are stiffened adequately to withstand handling loads without pressure, but require internal pressure to withstand flight loads; the SpaceX Falcon describes this as though it is unusual, but it is actually the normal case.
- Recoverable and Reusable: Whatever range Lilmax winds up with, at least the first set of strap-on modules will be reusable, even if they hit dry land. Dry land may be preferable because trucks are cheaper than ships.
- High tank pressure ensures simplified turbopump design, and large safety margins for flight loads and recovery.
- Modules will have a blowdown phase late during their operation (this is also normal for most boosters), what is different with Lilmax is that after shutdown (for recoverable modules only), the tank residuals boil off and rebuild pressure for recovery. During the blowdown phase, the engines are throttled back because less suction pressure is available for the turbopumps.
Bluestar: 8000kg LEO payload fully reusable booster and orbital service vehicle
Earth to Orbit Centerpiece of: Station Access Plan (status=stub), used to be International Space Transportation System
Bluestar has evolved considerably since I first drew it up in 2001. Since then, I have discovered that putting wings on spacecraft is about as silly as equipping submarines with screen doors and wings to allow them to fly through the air. The Space Shuttle suffers horrendous expense because its wings, control surfaces, hydraulics, and landing gear (including 100lb of tire air) are carried all the way to orbit and do absolutely nothing to add to the Shuttle's functionality in space. 60 tonnes of nothing more than ballast until less than half an hour before landing. 55% of the Shuttle's orbital mass is used only for the last 0.17% of a twelve day mission. At first, Bluestar was based on Saenger II and Ashford Spacebus (http://www.bristolspaceplanes.com/projects/spacebus.shtml ... from memory, yikes!) but is now based on Lilmax.
Bluestar now implements a ballistically recoverable upper stage for ascent on the Lilmax lower stage modules. For basic LEO (Low Energy Orbit) services, more than one variant may be required. The satellite payload version is described at http://www.openluna.org/wiki/index.php/Bluestar. A station logistics variant would better resemble the Sprint Crew Ferry (http://aftercolumbia.tripod.com/deltasprint/ where you will see why I lament not preserving Brian Heick's excellent 3D artwork of this concept in support of the Orbiter Mars Direct Project.) Inside such a ferry would be the racking one would normally see inside a Leonardo class module or a SpaceHab Logistics module.
Freezerburn: 100 tonnes and up
Centerpiece of: Mars Access Plan (Phase II)
The colonization of Mars, and possibly other destinations, will require cheap heavy lift services, a very challenging mission. Heavy lifters will also be required for space hotels, and in the unlikely event they should prove economical, solar power satellites.
- Basic Freezerburn core is formed by adding structural end pieces to four Lilmax modules. These four modules then form the basic Freezerburn core stage almost for free. This is not unprecedented at all: the Saturn IB stage was formed very similarly from eight Redstone tanks and one Jupiter tank.
- Up to 12 Lilmax modules can be strapped onto the core. At least four would normally be strapped onto the core, because with only the core, Freezerburn's capacity would not exceed that of the largest Lilmax configuration, which uses five modules.
- A very large, 9m diameter upper stage is used on Lilmax. It is not recoverable, but may be reusable by incorporating it into structures in space. The most likely propellant combination for this upper stage is oxymethane, or LOX/LNG (LNG being 16% ethane, 84% methane, with trace amounts of hydrogen sulphide and helium.)
- The most likely growth option is to extend the upper stage into a booster core which sits on top of the four module core already in place. On to this, Lilmax strap-on modules above their equivalents strapped to the first stage would be attached to the upper stage. Intermediate is to use the widebody core directly on the first stage with an older upper stage on top of it.
This concludes the Ascent Roadmap introduction!!
The Ascent Roadmap is also a significant part of the OpenLuna Wiki (which will eventually begin to concentrate on the Lunar Access Plan.) The following is from memory, and should be very similar in jist to what you will find at http://www.openluna.org/wiki/index.php/Ascent_Roadmap but not verbatim.
First, I highly recommend the book by John R. London III, LEO On The Cheap hosted at http://www.dunnspace.com/. It has only one glitch, as does almost all advocates of Minimum Cost Design (MCD) boosters: it has underestimated the scaling problem of total thrust pressure, which makes it very difficult to design large pressure-fed boosters with payloads above 20 tonnes to Low Energy Orbit.
Payload Class Boosters:
Prochron: 3kg to Low Earth Orbit.
Earth-to-Orbit Centerpiece of: Hobby Access Plan (status=stub)
Stage One: off the shelf high power rocket motors of N impulse class. These motors provide the initial thrust to lift the booster out of the launch tower and give it enough speed so that it's passively stable design has enough speed to avoid excessive weathervaning. They are jettisoned after six seconds, and are recovered the same way as high power rockets are always (sic) recovered: parachute and puppy dog.
Stage Two (ver. 0811A): A core stage with fins, a single motor, oxyfuel (probably oxypropane) propellant combination. Additional stages, if applicable, are stacked on top. The entire assembled vehicle fits under a total impulse class of T, allowing it to be operated as an amateur rocket...as long as it stays under 150km peak altitude.
Stage Two (ver. 0811B): 3 common modules, the sort inspired by OTRAG, strapped to a core stage. Each module is a blowdown single motor stage (probably oxypropane). This means that Prochron amateur rockets could use this module, and possibly be far smaller than ver. 0811A.
Stage Three (ver. 0811A): a single common diameter stage stacked on top of the second stage core, with a small pressure-fed oxyfuel motor, smaller than that in Stage Two.
Stage Three (ver. 0811B): The single module in between the Stage Two modules, carrier of Stage Four (if applicable)
Stage Four: a small upper stage designed to apply a precise impulse bit to the payload to get it into the proper orbit and correct for errors in earlier stages. It carries a small cold gas RCS system.
Operation: Prochron flies passively (or semi-passively) through Stages One and Two, which operate in the atmosphere. Stages Three and Four require active guidance and stabilization to correct from Stages One and Two, and because without air, fins don't work. The fairing is jettisoned during Stage Three. The payload is based on CalPoly's Cubesat (http://www.cubesat.org/). 3kg forms a single "pod" of CubeSats.
Symtex: Up to 500kg to orbit
Earth-to-Orbit Centerpiece of: nothing so far
A modular pressure-fed launch vehicle intended to fill the niche underneath the Orbital Sciences Pegasus and Minotaur class boosters. If it entered service as a commercial launch vehicle, it would have no competition, except for the very largest configuration, which nearly matches Pegasus/Minotaur performance.
Common Motor: a single oxyfuel (probably oxypropane, possibly same as Prochron Stage Two ver. 0811A) used by all stages except for the upper stage, which mounts a smaller Space Motor (probably same as Prochron Stage Three).
Strap-on Module: Wide enough only to mount one Common Motor, this small module provides high lift-off thrust for about 40 seconds.
Core Modules: Mounts any number of motors from one to four (including the possibility of a single high expansion version for a second stage.) They will probably be cut to two different lengths. Try not to think of them as putty-like: stretching and cutting stages is not so simple.
Upper Stage: Contains the guidance system, is multiple maneuver capable, and contains the payload interface and vehicle electrical sources. A special type of internal gear expander coupled pump (think "displacement turbopump") is being considered. It is based on the StarRotor design (http://www.starrotor.com/), and StarRotor Corporation has been queried for its potential use. Special thanks to them for providing After Columbia Project with basic application formulae and the University of Idaho ALLPROPS software.
Operation: Symtex is actively guided all the way to orbit, but it is intended that it be passively stable until at least the first staging event. It therefore does not require a tower or rail for weathervaning control. For conventional launch vehicles, typically extensive balloons and often patrol aircraft are used to measure winds aloft. To avoid the expense, Symtex will provide extra margin for corrections, and extra thrust to get out of the atmosphere quickly, and thus mitigate the performance effects of wind shear. The smallest configurations use strap-configured core stages, who's core operates primarily as a second stage. The largest configurations will probably use Long Cores strapped by Short Cores, plus a final Short Core as a second stage. The upper stage will probably be used in such configurations for circularization maneuvers.
Kilder: 1000 to 8000kg Low Energy Orbit
Earth-to-Orbit Centerpiece of: Lunar Access Plan
Kilder features an pressure-fed oxyfuel (probably oxykerosene) core which must be strapped in order to rise from the pad. The strap-on system provides the first stage, and a squat, rotorpump engined (probably oxyethylene) upper stage comprises the third stage. The most advanced of the strap-on systems carry Lilmax turbopump engines, once that engine has been developed for Lilmax.
Lilmax: 15 to 50 tonnes Low Energy Orbit
Earth-to-Orbit Centerpiece of: Mars Access Plan
Lilmax begins to approach the size and complexity of typical boosters in terms of its systems and launch configurations, even though it is made of spun/rolled steel. Compared to extant boosters, it considers some very unusual features for its lower stage module, along with a more conventional upper stage. The modules come in a single length, without stretching or cutting down, however the upper stage will probably have two different sizes to accomodate different payload levels and final orbits. Unusual features (unusual both to "big dumb boosters" and conventional launch vehicles) are:
- Segmented tank construction: This allows rail and truck transportability of individual segments, which form a much larger stage when assembled. This is currently done with the Shuttle's solid boosters.
- Crossfeeding of propellants from strap-ons to core, allowing the core to remain full until the strap-ons burn out and are jettisoned.
- Pressure-stabilized structure. The normal tank pressure is 200psig with a burst factor of safety of 2.0, so it may be able to stand on its own anyway. If it can't, we'd rather use cradles and removable internal webs during transport than add stiffeners to the design. Most boosters are stiffened adequately to withstand handling loads without pressure, but require internal pressure to withstand flight loads; the SpaceX Falcon describes this as though it is unusual, but it is actually the normal case.
- Recoverable and Reusable: Whatever range Lilmax winds up with, at least the first set of strap-on modules will be reusable, even if they hit dry land. Dry land may be preferable because trucks are cheaper than ships.
- High tank pressure ensures simplified turbopump design, and large safety margins for flight loads and recovery.
- Modules will have a blowdown phase late during their operation (this is also normal for most boosters), what is different with Lilmax is that after shutdown (for recoverable modules only), the tank residuals boil off and rebuild pressure for recovery. During the blowdown phase, the engines are throttled back because less suction pressure is available for the turbopumps.
Bluestar: 8000kg LEO payload fully reusable booster and orbital service vehicle
Earth to Orbit Centerpiece of: Station Access Plan (status=stub), used to be International Space Transportation System
Bluestar has evolved considerably since I first drew it up in 2001. Since then, I have discovered that putting wings on spacecraft is about as silly as equipping submarines with screen doors and wings to allow them to fly through the air. The Space Shuttle suffers horrendous expense because its wings, control surfaces, hydraulics, and landing gear (including 100lb of tire air) are carried all the way to orbit and do absolutely nothing to add to the Shuttle's functionality in space. 60 tonnes of nothing more than ballast until less than half an hour before landing. 55% of the Shuttle's orbital mass is used only for the last 0.17% of a twelve day mission. At first, Bluestar was based on Saenger II and Ashford Spacebus (http://www.bristolspaceplanes.com/projects/spacebus.shtml ... from memory, yikes!) but is now based on Lilmax.
Bluestar now implements a ballistically recoverable upper stage for ascent on the Lilmax lower stage modules. For basic LEO (Low Energy Orbit) services, more than one variant may be required. The satellite payload version is described at http://www.openluna.org/wiki/index.php/Bluestar. A station logistics variant would better resemble the Sprint Crew Ferry (http://aftercolumbia.tripod.com/deltasprint/ where you will see why I lament not preserving Brian Heick's excellent 3D artwork of this concept in support of the Orbiter Mars Direct Project.) Inside such a ferry would be the racking one would normally see inside a Leonardo class module or a SpaceHab Logistics module.
Freezerburn: 100 tonnes and up
Centerpiece of: Mars Access Plan (Phase II)
The colonization of Mars, and possibly other destinations, will require cheap heavy lift services, a very challenging mission. Heavy lifters will also be required for space hotels, and in the unlikely event they should prove economical, solar power satellites.
- Basic Freezerburn core is formed by adding structural end pieces to four Lilmax modules. These four modules then form the basic Freezerburn core stage almost for free. This is not unprecedented at all: the Saturn IB stage was formed very similarly from eight Redstone tanks and one Jupiter tank.
- Up to 12 Lilmax modules can be strapped onto the core. At least four would normally be strapped onto the core, because with only the core, Freezerburn's capacity would not exceed that of the largest Lilmax configuration, which uses five modules.
- A very large, 9m diameter upper stage is used on Lilmax. It is not recoverable, but may be reusable by incorporating it into structures in space. The most likely propellant combination for this upper stage is oxymethane, or LOX/LNG (LNG being 16% ethane, 84% methane, with trace amounts of hydrogen sulphide and helium.)
- The most likely growth option is to extend the upper stage into a booster core which sits on top of the four module core already in place. On to this, Lilmax strap-on modules above their equivalents strapped to the first stage would be attached to the upper stage. Intermediate is to use the widebody core directly on the first stage with an older upper stage on top of it.
This concludes the Ascent Roadmap introduction!!
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