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Orbit-Capable Homemade Rocket


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So i have this ambition that we can send homemade rockets to orbit. I've seen some pretty cool videos on homemade rockets reaching the Karman line.

 

What do we need to make a rocket that's orbit-capable? By that i mean it has enough delta-V to reach an altitude of above 100km and orbit the earth once.

These are some of the considerations i would think separates "homemade" from "professional". I'm researching if a homemade rocket is truly possible, or not.

1. The rocket should not use any highly-pressurized fuel, or hard-to-attain fuels such as liquid hydrogen. Kerosene and LOX should be easy to get, so is solid fuel.

2. Fuel should be storable between temperatures of 10C and 70C, and in a pressure not exceeding 100 bar. This excludes oxidizer/LOX.

3. The rocket should not contain any expensive, rare metals(such as niobium).

4. Rocket core should be not bigger than 10m in height, or 1.5m in diameter. Rocket can have multiple strap-on cores, asparagus is fine.

Also, the rocket built should be made with materials accessible to the common man. Milled machine parts and metal are fine, just not space-grade. Simplicity is also another factor, the rocket should have as little parts/moving parts as possible.

 

My initial idea of a homemade rocket that can reach orbit is one that burns kerosene and LOX, with 4 small engines. It is about 8 metres high, and 1 meter in diameter.

During initial ascent, an elastic rope will grab on one side of the rocket, tilting it slightly. It will snap after about 2~3m of extension. 4 fixed fins at the bottom of the rocket will put it in spin stabalization. The stage will burn for about 57 seconds, after which it will separate, revealing a second stage about 1m in length, and 80cm in diameter. The second stage will use monopropellant and an extended rocket nozzle to "reach" orbit.

Crunching the numbers, however, it was terribly inefficient and could barely reach a decent suborbital trajectory.

With no payload in mind, how would you design yours?

Edited by Rdivine
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35 minutes ago, Rdivine said:

I've seen some pretty cool videos on homemade rockets reaching the Karman line.

The issue with that is that the step from "reaches the Karman line" to "enters orbit" is not something like the last 20% or so.

Much to the contrary, reaching the Karman line is like the first 20% or so (my half-educated guesstimate). So, see those amateur rockets that managed the feat? And how large they are and how hard they were to build? Make that five times as big/hard. At minimum, you need to stage once. Single-stage, it's not going to happen. The Falcon 9 first stage can just barely, ever so barely manage it without carrying a payload (apart from a nosecone), and that's a professionally built launch vehicle with a mass fraction of 30:1 and engines with a base TWR of 200.

Also, that rocket in the video? Went 100,000 feet, not meters. To even reach the Karman line, it would have to go more than three times that high!

 

35 minutes ago, Rdivine said:

These are some of the considerations i would think separates "homemade" from "professional".

You might want to define what you mean with "homemade" here, especially considering what I wrote above. That term can mean almost anything. Is the location important where the parts are assembled (and if so, are you allowed to bring in parts manufactured externally for assembly)? Or is it important to you that the people building it are not trained professionals? If so, what separates a trained professional from someone who's not? His employment status, his education, his level of interest in all things aerospace? How do you measure that?

...So yeah :P Please define some basic ground rules.

 

35 minutes ago, Rdivine said:

1. The rocket should not use any highly-pressurized fuel, or hard-to-attain fuels such as liquid hydrogen. Kerosene and LOX should be easy to get, so is solid fuel.

2. Fuel should be storable between temperatures of 10C and 70C, and in a pressure not exceeding 100 bar. 

Rule 2 disqualifies LOX, just FYI. You'll then be forced to fly with gaseous oxygen because all other options are highly toxic. And gaseous oxygen is not a good oxidizer because its density is poor, lowering your mass fraction (and thus your dV). So yes, you should definitely allow LOX; even as a moderate cryogenic substance, it's still not as dangerous as most room temperature liquid oxidizers. The worst it does to your project is requiring a fuel loading infrastructure at the launch site.

Solid fuel is also "hard to attain". At least high grade grade solid fuel. Not because the chemicals are restricted, but because you need sophisticated machinery to cast the grain (contguous block of solid fuel). Even minor imperfections in the grain can wreck a high power solid rocket in a matter of seconds. And when such a booster goes, the results can be... shall we say... spectacular. The "run until your feet bleed if you value your life" kind of spectacular. :P It literally "rains fire".

 

Edited by Streetwind
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I say its hard, one indication is that both North Korea and Iran have used years to manage it even with huge budgets 
No they might not use LOX as their space program is mostly an cover for the missile program, on the other hand its also about propaganda and if an LOX rocket was easy they would just use that. 

First issue is size, second is staging, last the flight control system you need an gravity turn. 

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You will need a fairly sophisticated guidance system/autopilot.

My gut says that the authorities might want to talk to you about attaching guidance systems to huge rockets however...just a hunch.

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@p1t1o There's a legal limit to amateur rockets right? IIRC they can't reach a hight limit or they can be considerate a missile or something like that. (at least in a documentary I saw about amateur rockets int US, I'm not from there and I don't know about other countries)

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31 minutes ago, Motokid600 said:

I'd say the karman line isn't even 5 percent of the flight to orbit. There's also the vast amount of infrastructure you need to launch an orbital rocket. All in all its not something an ameture hobbyist can do.

It is more than you think, because you incur severe gravity losses through burning straight up.

An orbital rocket burns a lot longer, sure, but it does most of this burning sideways, which doesn't incur gravity drag. A suborbital hopper performs 100% of its shorter burn under 100% gravity drag. And since the final height is comparable to the height at which an orbital rocket goes fully towards the horizon, you can make a first order approximation about the relative magnitudes of gravity drag being at least somewhat similar. A refinement will likely lead to the suborbital rocket getting away with less, but not nearly as much less as you think.

I suppose if you wanted a better approximation, you could load up a Realism Overhaul install and measure the dV required for a suborbital launch. Since dV to low Earth orbit is a known quantity (ca 9.5 km/s), for your estimate to work out, the suborbital rocket would have to reach 100 km altitude using less than 475 m/s. Which is pretty unrealistic, as this isn't nearly enough for a rocket to escape stock Kerbin's 70 km atmosphere. In fact, if 475 m/s was applied instantly at launch and there was no atmosphere whatsoever, the vehicle would not be able to rise even 20 kilometers in the 47 seconds it has before gravity alone will have nulled out its velocity.

Edited by Streetwind
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7 minutes ago, Van Disaster said:

Remember these guys? http://copenhagensuborbitals.com/ ( they hang around on here sometimes ) not sure if you'd call that "homemade", but you can get some idea of the problems involved and the solutions available for non-commercial efforts.

CopSub is totally awesome, but in regards to the topic of this thread, it should be noted that (as their name implies) they are not building an orbital rocket. Most of their high up-front effort is due to planning to build a manned launch vehicle, which requires far more of both oomph and engineering exactness as an amateur sounding rocket. :wink:

Still, the youtube channel has lots of commented videos on the design and production of a liquid bipropellant rocket engine, on control authority, electronics, fuel handling, structural considerations and so on and so forth. Pretty sure their Nexo 1 sounding rocket launch is coming up this summer, as they already recently cold-soak-tested the fully assembled rocket. (After that comes Nexo 2, and then the manned launcher.)

Edited by Streetwind
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29 minutes ago, p1t1o said:

You will need a fairly sophisticated guidance system/autopilot.

My gut says that the authorities might want to talk to you about attaching guidance systems to huge rockets however...just a hunch.

2 minutes ago, VaPaL said:

" The launch vehicle is based on the Minuteman II missile ..."

This is exactly what I was talking about :wink:

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One popular combination is nitrous oxide and a rubberish solid.  The oxidizer can be fairly easily stored (car modification enthusiasts leave tanks of liquid nitrous oxide in the car, and often I suspect in the engine compartment).  The fuel is even easier to deal with, and is simply molded and poured (and doesn't have the issues Streetwind mentioned, especially if you can separate it from the oxidizer).

To get an idea of the problem you are facing, find out what the expected ISPs you might get from available engines and plug them into the rocket equation (don't forget the dry weights).  Then see just how much fuel you will need to get up to 8000m/s (plus gravity and aero losses).  I'm fairly sure that no 8m rocket will ever get into orbit (I'd expect about 4-5 stages of model rocket/solid motors on top of your liquid rockets* (I think at least one place sells the "real deal" in chemicals) to finally get a nanosat into orbit.

* basically because there isn't a size limit on SRBs.  You just strap them on and light them, so you can wind up with a final stage with a few grams of dry weight and tens of grams of fuel weight.  Expect to attach a large nozzle as any available solid rocket will be designed for 1 atmosphere.

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1 hour ago, Camacha said:

I think people dreaming about homemade orbital rockets severly underestimate the difference between shooting straight up and reaching a proper orbit.

Never underestimate the power of rose tinted glasses- I have them, too! Something that's always had me buzzing with excitement is the possibility of a tiny (~4g) payload. One of my jobs over the years has been the lead engineer of a many-user microtechnology fab, where we designed and made all sorts of tiny gyroscopes, photovoltaics, lasers, actuators, you name it. They could be via'ed and bonded together to make a heck of a little payload. Plus the preponderance of miniaturized low power goodies found in phones. Oh my! The things you can fit in a few grams.

My dream (and of course it is only that) would be to lob a 2-3lb payload up to the karman line using traditional (N2O hybrid) high-power amateur rockets, then use the payload's slightly-better-than-estes staged solid rockets to push the 4g payload up to orbital speeds. It would then use its little laser (aimed with MEMS mirrors and MEMS guidance gyroscopes) to sweep a "I made it! Space it big." signal to a waiting directional receiver on the ground.

I do love dreaming :)

30 minutes ago, wumpus said:

One popular combination is nitrous oxide and a rubberish solid

They use this in my favorite video on burgeoning in to amateur high-power rockets: https://www.youtube.com/watch?v=BJppeRWSD94 (They do a great job, but had a very kerbal experience....)

Edited by Cunjo Carl
fixed a very emberassing typo.
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2 hours ago, p1t1o said:

You will need a fairly sophisticated guidance system/autopilot.

My gut says that the authorities might want to talk to you about attaching guidance systems to huge rockets however...just a hunch.

That's why you don't use a guidance system, but rather an "automated stabilizer" or you'll land rather quickly in unpleasant ITAR territory.

 

 

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5 minutes ago, Kerbart said:

That's why you don't use a guidance system, but rather an "automated stabilizer" or you'll land rather quickly in unpleasant ITAR territory.

ITAR only applies when you are in the US, or want to transport stuff from or to it. Even though restrictions might apply in the rest of the world, ITAR is not one of your worries there. Super accurate GPS stations for everyone! :D

It is funny how many people on the forums assume everyone is talking about the US. People tend to make statements with far-reaching implications based on the assumption that things would be happening in the US, but without mentioning that. This is a wildly international forum, Squad is from Mexico, large portions of the visitors are from Europe, Australia and other portions of the world. If you make statements about judicial matters, be sure to include the area it applies to. In most cases, the difference from country to country is not really big, but when it comes to law, it can be night and day depending on whether you stepped left while at the border, or right.

Edited by Camacha
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11 minutes ago, Camacha said:

ITAR only applies when you are in the US, or want to transport stuff from or to it. Even though restrictions might apply in the rest of the world, ITAR is not one of your worries there. Super accurate GPS stations for everyone! :D

It is funny how many people on the forums assume everyone is talking about the US. People tend to make statements with far-reaching implications based on the assumption that things would be happening in the US, but without mentioning that. This is a wildly international forum, Squad is from Mexico, large portions of the visitors are from Europe, Australia and other portions of the world. If you make statements about judicial matters, be sure to include the area it applies to. In most cases, the difference from country to country is not really big, but when it comes to law, it can be night and day depending on whether you stepped left while at the border, or right.

Tell me what European country is totally cool with launching guided missiles from your backyard. I really like to know. Australia is mostly desert, so I'm sure it's totally fine to launch privately owned ICBM's without any paper work. But I think that 90% of the people here on the forum will run into issues with, if it's not ITAR, some very similarly restrictive legislation when it comes to launching anything that reaches an altitude of even 10km or more.

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7 minutes ago, Kerbart said:

Tell me what European country is totally cool with launching guided missiles from your backyard. I really like to know. Australia is mostly desert, so I'm sure it's totally fine to launch privately owned ICBM's without any paper work. But I think that 90% of the people here on the forum will run into issues with, if it's not ITAR, some very similarly restrictive legislation when it comes to launching anything that reaches an altitude of even 10km or more.

Regulations vary wildly from country to country and for very different reasons too. ITAR is very arms oriented, while other nations try to prevent mishaps with airliners or classify rockets as fireworks. This means that if a permit is required, it should often be very doable. ITAR seems to be a rather tough cookie to crack.

I checked the regulations of some of the nations I frequent and at least one seemed to be okay with guided rockets. It does limit both engine size and weight, though, so orbital rockets would be out of the question.

Edited by Camacha
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2 hours ago, wumpus said:

One popular combination is nitrous oxide and a rubberish solid.  The oxidizer can be fairly easily stored (car modification enthusiasts leave tanks of liquid nitrous oxide in the car, and often I suspect in the engine compartment).  The fuel is even easier to deal with, and is simply molded and poured (and doesn't have the issues Streetwind mentioned, especially if you can separate it from the oxidizer).

The problem with these so-called hybrid rockets is that they don't scale well.

Since rubber is not a good fuel and nitrous oxide is not a good oxidizer (meaning, not as good as the cryogenic LOX or toxic hypergols), your Isp isn't that amazing. Which means you need a large propulsion unit. But hybrids in general have massive issues with vibration-induced uneven burning, which causes the motor to vibrate more, which causes even more uneven burning... yeah, you get the idea. With a small motor it doesn't matter much, but the larger you make it, the more erratic the combustion becomes, and the more vibration is inflicted on the vehicle.

Case in point: Scaled Composites won the Ansari X-Prize in 2004, using a small suborbital spaceplane driven by such a rubber/NOX hybrid motor. They then entered a joint venture with the Virgin group that is now known as Virgin Galactic, and thought that they'd upscale the vehicle and fly customers by 2009. But, turns out it is 2016, and they still haven't fully flight qualified a SpaceShipTwo vehicle. And the vast majority of delays were due to the motor, which just didn't want to scale up peacefully. They blew up more than one, even killing a worker in the process, and went as far as examining completely different fuel choices (but still sticking to the hybrid concept) in hopes of solving the issue. Then finally, after some ten years, they ended up with something that stayed within acceptable tolerances, but it had less performance than hoped, and SpaceShipTwo will not quite be able to reach the Karman line during commercial operations.

(And then of course, while testing that new motor, they had that unfortunate loss of vehicle and life due to piloting error, which is why the delays continue to this day...)

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The thickness of air has a lot to do with it. At small engine sizes, the air is comparatively thick enough to damp destructive resonance and vibrations. Not so much with orbital-class SRBs or hybrids.

That being said, you can look at Sugar Shot to Space for a Karman Line version.

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2 hours ago, kiwi1960 said:

It is illegal to actually exceed a certain height.... and if you achieve orbit, they would probably lock you up for life... citing a navigation hazard for REAL satellites, ships or stations.

Yea, that's where the infrastructure comes into play. And that's what brings orbit out of the amateurs hands and into professional ones. 

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That is to say it cannot be done, in the USA, you will need clearance from the FAA to exceed the amateur height restrictions and probably permission from NASA to enter an orbit where it won't damage anything.. it can be done... but I'm thinking it might be easier to get blood from a stone.

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