Attempt towards an amateur orbital rocket.

RGClark

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Unfortunately OpenRocket and RasAero do not have the capability for doing orbital trajectory sims. The best you can do with these programs is see if you can get a rocket that can achieve both the tangential, i.e., horizontal velocity for orbit and the needed altitude above 100 km. This though will be a rocket traveling straight-up so isn't really showing an actual trajectory to orbit. Attached is an attempt at such a rocket.

It is derived from the Cesaroni rocket that powers Up Aerospace's Spaceloft XL suborbital rocket. It consists of 4 stages with the first stage being the Cesaroni rocket. For the subsequent stages we will use a smaller motor by a factor of 1/4th at each stage. So the 2nd stage will be 1/4th that of the Cesaroni, the 3rd will be smaller by an additional factor of 1/4th, and the fourth stage smaller again by an additional factor of 1/4th.

Here's the specifications on the Cesaroni motor:

Spaceloft_engine.jpg

Here's the thrust data for the Cesaroni motor in RASP format from its .Eng file:

;
; Cesaroni Booster motor for UP Aerospace.
; @File: CTI_UPA-264-C.eng, @Pts-I: 42, @Pts-O: 31, @Sm: 0, @CO: 5%
; @TI: 438207.0, @TIa: 437890.0, @TIe: -0.05%, @ThMax: 52454.9, @ThAvg: 37051.4, @Tb: 11.827
; Exported using ThrustCurveTool, www.ThrustGear.com
S37029 265 3018 P 186.8801 242.672 NEW
0.037 540.773
0.061 1406.008
0.073 13086.69
0.086 48561.4
0.147 52454.9
0.257 50616.3
0.355 49859.2
0.698 48453.2
0.918 46073.8
1.175 44667.8
1.591 43586.3
2.338 42829.2
4.199 42288.4
4.701 41855.8
8.006 35907.3
9.658 32230.0
10.234 26606.0
10.368 23577.7
10.637 21414.6
11.176 21414.6
11.262 21847.2
11.335 21090.1
11.445 19575.96
11.543 17737.33
11.629 14600.85
11.69 11464.37
11.764 6813.73
11.825 4001.72
11.911 2163.09
12.021 648.927
12.376 0.0
;


The format of .ENG files is described here:
==============================================================

RASP header


  1. The common name of the motor; just the impulse class and average thrust.
  2. The casing diameter in millimeters (mm).
  3. The casing length, also in millimeters.
  4. The list of available delays, separated by dashes. If the motor has an ejection charge but no delay use "0" and if it has no ejection charge at all use "P" (plugged).
  5. The weight of all consumables in the motor. For solid motors this is simply the propellant itself, but for hybrids it is the fuel grain(s) plus the oxidizer (such as N2O). This weight is expressed in kilograms (Kg).
  6. The weight of the motor loaded and ready for flight, also in kilograms.
  7. The motor manufacturer abbreviated to a few letters. NAR maintains a list of manufacturer abbreviations on page 2 of the combined master list.
==============================================================

The lines preceded by a ; symbol are regarded as comments and are not interpreted by the sim programs.

For the smaller upper stages, I successively made the dry mass, propellant mass, length, and thrust smaller by a factor of 1/4th. I kept the same diameter for each stage. I didn't change the comment lines, other than saying it's one-quarter size, since I didn't know what they meant anyway. Here's the thrust data for my created 2nd stage in RASP format:

;
; Cesaroni Booster motor for UP Aerospace - quarter size.
; @File: derived from CTI_UPA-264-C.eng, @Pts-I: 42, @Pts-O: 31, @Sm: 0, @CO: 5%
; @TI: 438207.0, @TIa: 437890.0, @TIe: -0.05%, @ThMax: 52454.9, @ThAvg: 37051.4, @Tb: 11.827
; Exported using ThrustCurveTool, www.ThrustGear.com
Q9000X 265 755 P 46 61 NEW
0.037 135
0.061 350
0.073 3270
0.086 15411
0.147 13110
0.257 12654
0.355 12465
0.698 12110
0.918 11518
1.175 11166
1.591 10900
2.338 10707
4.199 10572
4.701 10463
8.006 8976
9.658 8057
10.234 6651
10.368 5894
10.637 5353
11.176 5353
11.262 5461
11.335 5272
11.445 4894
11.543 4434
11.629 3650
11.69 2866
11.764 1703
11.825 1000
11.911 540
12.021 162
12.376 0.0
;


Note the thrust values are 1/4th those of the full-size Cesaroni motor. For center burning solid motors, the thrust is made proportionally larger or smaller according to the length of the motor since that determines the burning surface area.

The 3rd and 4th stages are made successively, proportionally smaller as described.

For the orbital velocity for low Earth Orbit, that is ~7,800 m/s. But for low latitude launch sites such as Cape Canaveral you get ~400 m/s for free from the Earth's rotation. So I took the required velocity needed to be attained as 7,400 m/s. I simulated no airframes by given the body tubes in the OpenRocket sim a mass of 0 kg.

The payload mass is taken as 500 grams. For this ~330 kg gross mass rocket, this is a payload to gross mass fraction of 1 to ~660.

Issues and Problems.

1.)Notable I used a rounded ogive nose cone rather than conical or von Karman shape. The reason is a quirk in OpenRocket is that it sometimes for hypersonic flights will give a higher altitude for a short, squat nozzle than a long, pointed one. Aside from that, I also didn't assign a mass for the nose cone since I really didn't know what the size and shape it would wind up being. And anyway based on orbital rockets it should be only a fraction of the payload mass anyway. For example for the Falcon 9, it's payload fairing is at about 2 tons for an expendable payload of ~23 tons. So based on that, a 500 gm payload might need only a 50 gm nose cone.

2.)Not really an issue or problem but OpenRocket counts stages downwards from top to bottom, in contrast to the usual practice in the industry. Also, it starts up always with a single stage present as default which it calls the "Sustainer", even if you don't give that "stage" a motor. So in this case OpenRocket calls this rocket a 5 stager with the top stage, which it calls the 1st stage, only consisting of the nose cone and payload. I could probably change that by editing the names but didn't bother to.

3.)I am worried about the stability of the upper, powered stages. The rocket overall has the center of gravity CG ahead of the center of pressure CP, but for each stage above the booster, the CG is behind the CP. I'm thinking for the top most stages that won't matter since they fire at near vacuum. But it should matter for the stage above the booster stage.

4.)I'm interested in find out what the vacuum Isp is for the upper stages. We might be able to get improved performance using longer nozzles.

Attached is the .ORK file using OpenRocket version 15.03.

Robert Clark

OpenRocket screen capture.JPG
 

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RGClark

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I forgot you won't be able to run this OpenRocket sim, unless you have copies of the thrust curves as .ENG files for each of the stages. They are attached. You save them to the Thrustcurves subfolder to your OpenRocket folder.

Bob Clark
 

Attachments

  • SpaceLoft Motor - one sixteenth size.eng
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  • SpaceLoft Motor - one sixty-fourth size.eng
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  • SpaceLoft motor - quarter size.eng
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  • SpaceLoft motor.eng
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rharshberger

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You seem to have an obsession with using hobby software to do things it was never intended to do and the features you seem to want to see are useless to 99% of hobbyists, for the last 1% there are probably professional tools that will do what is desired. So why should developers waste time on features that few if any are likely to use.
 

prfesser

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Lots of us play with OR in many ways, but it's highly doubtful that the rocket described would be anything more than a fun diversion for a rainy afternoon or two. If this had even the most remote possibility of success, wouldn't any number of countries jump at the approach?

Japan's SS-520 is the smallest rocket (so far) to send a payload to orbit. That little item is 10 m tall and half a meter in diameter, and weighs 2600 kg wet. Unlikely that the above approach with commercial solids would work even if you TRIPLED the number of motors in each stage.

"In theory there is no difference between theory and practice...but in practice...there is." :)
 

boatgeek

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I see this is a minimum diameter rocket with no recovery systems or electronics. How will you recover the lower stages safely* and ignite the upper stages? How will you maintain trajectory once the atmosphere is no longer effective? I don't see any provision for steering nozzles or the like. If you have steering nozzles, why not just dump the fins and their drag/weight?

Rather than trying to force OpenRocket to do this, you could calculate the mass of motor, airframe, and associated systems needed to achieve orbital velocity from an apogee at orbital altitude. Then determine the rocket necessary to loft that mass to orbital altitude. Sure, it's a little bit of a hack since you'll start turning a real orbital rocket horizontal well before orbital altitude, but you'll be using roughly the same total amount of energy. It'll at least get you within an order of magnitude.

Alternatively, you could use another hobby program better suited to calculating orbital mechanics: Kerbal.

* At a bare minimum, the first and likely the second stages will need some kind of recovery. The third stage might be going fast enough to burn up on re-entry.
 

3stoogesrocketry

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Let's not forget you need to design and formulate your own motors. A 12 second burn baby M motor is a neat trick , let alone a motor with "good mass fraction " and "good vacuum ISp" to make this work .
 

cbrarick

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* At a bare minimum, the first and likely the second stages will need some kind of recovery. The third stage might be going fast enough to burn up on re-entry.
You'll need to explain that requirement to all others who''ve gotten anything into orbit with the exception of SpaceX and maybe the NASA shuttle team. Everyone else has just let them drop.
 

boatgeek

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You'll need to explain that requirement to all others who''ve gotten anything into orbit with the exception of SpaceX and maybe the NASA shuttle team. Everyone else has just let them drop.
That’s fair, and if this got far enough to actually move toward orbit the recovery of the lower stages would be the least of the concerns. For anything close to NAR or TRA codes, you would need to plan for recovery.
 

cerving

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I think this project would be outside the scope of TRA/NAR... you don't need to worry about the "down" part if you launch it over the Atlantic, although the FAA may require you to have a remote destruct feature.
 

Neutronium95

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So, this is just “goofin’ around with Open Rocket”, right? Not an actual project, correct?

I sure hope so. As someone said upthread, we don't remotely pretend to do orbital mechanics.

You must not be very familiar with his posting history then. He's been saying stuff like this on here and on other sites for years.

His original blog post

Thread where he abused RASAero

Reddit 1

Reddit 2

Reddit 3

All that said, I think that it might be possible to use Openrocket or RASAero to help get an idea of how big a small orbital rocket would need to be. You could use a spreadsheet to determine a stage configuration capable of attaining orbital velocity. Then treat that as an inert mass object that has to be lofted to the orbital altitude. doubt that it would be accurate, but it would be a fun exercise. I also suspect that the result would be a rocket at least as big as the SS-520, which would be far from easy, or even possible foran amateur or university team.
 
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Alan15578

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And the license/permit to make an orbital flight will cost more than the insurance.
We don't need no stinking...
Hold on, recalculating...
Does rocket exhaust stink?

I might suggest polishing up you engineering skills and designing an orbital rocket on paper. Then you could build a scale model rocket of that and fly it at your local park.
 

ThirstyBarbarian

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You must not be very familiar with his posting history then. He's been saying stuff like this on here and on other sites for years.

His original blog post

Thread where he abused RASAero

Reddit 1

Reddit 2

Reddit 3

All that said, I think that it might be possible to use Openrocket or RASAero to help get an idea of how big a small orbital rocket would need to be. You could use a spreadsheet to determine a stage configuration capable of attaining orbital velocity. Then treat that as an inert mass object that has to be lofted to the orbital altitude. doubt that it would be accurate, but it would be a fun exercise. I also suspect that the result would be a rocket at least as big as the SS-520, which would be far from easy, or even possible foran amateur or university team.

These posts seem a bit like a virgin arguing sex advice based on articles he’s read and hypothetical scenarios he’s “simulated” in adult video games.
 

Adrian A

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I have found this thread entertaining and occasionally informative. It's an interesting thought experiment to see just how far advanced amateur/semi-pro techniques could go. Just how small/light/inexpensive could the minimum orbital rocket be?

Unfortunately 0.5 Kg of "payload" would likely not cover the RCS system you would need for the final burn. But with a minimum-mass thrust vector control and some very small RCS for roll control, it might not need to be more than 1 Kg.
 

RGClark

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You seem to have an obsession with using hobby software to do things it was never intended to do and the features you seem to want to see are useless to 99% of hobbyists, for the last 1% there are probably professional tools that will do what is desired. So why should developers waste time on features that few if any are likely to use.

Quite a few of the high power experimenters would be interested in doing flights to the Von Karman line of 100 km. The experiences of the USC RPL student team that reached it, the Princeton University student team that would have succeeded if their sustainer ignited, Project Mesos that essentially reached it at 90 km, and the project by member Andrej Vrbec and Denis Banovic that likely reached it by a P to O motor rocket, as well as the FourCarbYen 2-stage rocket of Jim Jarvis, which simulations show without airframes also could reach it, prove commercial-off-the-shelf high power motors O, N, and even M with staging can reach the von Karman line if they don’t use airframes.

Airframes add significant weight to a rocket. For example, in the case of FourCarbYen, the two airframes weighed more than the dry mass of the two motors. In the professional industry, no suborbital or orbital space rocket uses airframes. But the point is any L3-level amateur who uses high power motors is capable of doing an airframe-free rocket by either using a fin can or directly attaching fins to the motor casings.

That Project Mesos and independently member Andrej were able to do high altitude ignition suggests this is also within the capabilities of advanced amateurs, needed for staging to reach 100km. And, I know I said this before but it’s among the all time best lines in movies, “What one man can do, another man CAN DO!”

The conclusion you draw is any L3-level amateur can do a flight to suborbital space. And after that? Some would be happy just staying there and that’s perfectly fine. But once you reach that goal the inclination is to imagine going further.

Bob Clark
 

StreuB1

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I have done my best to stay away from commenting on these threads, but I must ask for my own curiosity.

Is the OP aware that orbital means to orbit? And in that respect, it is not how high you go, it is how fast you need to go, sideways.

Comparing any of our awesome fellow members altitude accomplishments to anything with the word "orbital" in it makes me believe that the crux is being missed. The amount of energy to reach orbital velocity is relatively known, how you choose to get there is the hard part. Though what it comes down to is the minimum required energy, and that is far beyond what anyone in our circles, other than the few who work on orbital class rockets, are capable of.
 

StreuB1

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Also, lets stop calling cubesats that do not orbit the earth, a cubesat. As they are not, they are simply a payload. In order for a cubesat to be a cubesat, it must orbit the earth.
 

RGClark

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Lots of us play with OR in many ways, but it's highly doubtful that the rocket described would be anything more than a fun diversion for a rainy afternoon or two. If this had even the most remote possibility of success, wouldn't any number of countries jump at the approach?

Japan's SS-520 is the smallest rocket (so far) to send a payload to orbit. That little item is 10 m tall and half a meter in diameter, and weighs 2600 kg wet. Unlikely that the above approach with commercial solids would work even if you TRIPLED the number of motors in each stage.

"In theory there is no difference between theory and practice...but in practice...there is." :)

The Japanese rocket can get 4 kilos to orbit at a 2,600 kilo gross mass in 3 stages, about 1 to 650 payload to gross mass. This proposal is in the same range, but uses 4 stages.

Robert Clark
 

techrat

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There are a number of problems to overcome:

For one; reaching the Karman Line is generally straight up and down, it's been done many times by amateurs. Orbital is a whole different ball of wax. Not only do you need to get your rocket up into the 8-mile high range, you need to be going horizontally at at-least 17,500mph to avoid falling back down. This requires some form of active control. Servo-controlled fins will work for the first half of the flight, and then become useless when there isn't enough air for them to push against to be useful. Testbeds for high altitude flight such as the X-15 required control jets when the ailerons and rudder ceased to function. You could also gimbal the motors.

However, all this adds weight and complexity to the build. The rocket needs to know where it's supposed to be going and perform the work needed to get there. This means sensors and a computer, but also the needed mechanicals for the rocket to alter its course on its own. It's not easy, and that is one of the reasons only a handful of countries have orbital capability.
 

jsdemar

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The Japanese rocket can get 4 kilos to orbit at a 2,600 kilo gross mass in 3 stages, about 1 to 650 payload to gross mass. This proposal is in the same range, but uses 4 stages.
PLEASE do not use the Lambda 4S as existence proof that an amateur can make a small orbital solid motor launch system. The Japanese government spent years and a huge budget to prove it could be done. Once out of 5 attempts. It's just an outlier. It's not a road map to success for regular folks (or corporations, or governments). Just the opposite: almost 3 tons on the pad, millions of $$$, international regulatory cooperation, and never considered as an operational launcher. In other words, a barely successful demonstration flight which failed to prove a practicable system. After almost 50 years, almost no one has wasted time attempting all-solids to orbit.

For an example of a successful operational all-solids launch system, look at Scout. 25 tons on the pad, and the full efforts of the US military-industrial complex. Retired in 1994 and never replaced with an all-solids launch system.

Modeling a minimum all-solids to orbit vehicle is an interesting academic past-time. The closer one gets to considering all the physical (and regulatory) limitations, the more it becomes only academic.

Now back to souping up my gocart to run it in the Indianapolis 500.
 
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