Attempt towards an amateur orbital rocket.

[FredA]

I think the "bot" named Bob Clark needs to get out from behind the desk and actually build and fly a rocket.
Probably will need an intern or two to help ;-)

Of course a BT is not needed - but that's how you build "kit" rockets with easily replaceable/reloadable motors.
Few start machining their own motors and bolting on fincans.

 

[wclaybaugh2]

SpaceX was able to show it is possible to literally cut 90% off the development cost of an orbital rocket. Now imagine a scenario where you literally have zero labor costs, using university students willing to work for pizza during lunch breaks and college credits?

Bob Clark

There is a word for this sort of nonsense that begins with "Bull".

When in the government, I saw SpaceX's development costs for the expendable Falcon 9; they were much lower than the then industry standard but they were nowhere near this claim. Smilin' Bob appears to be simply making up these claims..."bull...." in other words.

I further observe that there appears to be no experience here of trying to build hardware with students...who characteristically take on far more than can be accomplished, essentially never reference previous experience (USC/RPL is an exception), and then slap something together that is visibly unlikely to work but insist on turning it on anyway. Those who have done it know that using students costs more and takes longer than using experienced personnel.


Bill

 

[StreuB1]

There is a word for this sort of nonsense that begins with "Bull".

When in the government, I saw SpaceX's development costs for the expendable Falcon 9; they were much lower than the then industry standard but they were nowhere near this claim. Smilin' Bob appears to be simply making up these claims..."bull...." in other words.

I further observe that there appears to be no experience here of trying to build hardware with students...who characteristically take on far more than can be accomplished, essentially never reference previous experience (USC/RPL is an exception), and then slap something together that is visibly unlikely to work but insist on turning it on anyway. Those who have done it know that using students costs more and takes longer than using experienced personnel.


Bill

It though does allow you access to an immense amount of free grant money that is flying around like the monkeys from a wizard of oz. We have seen this before, a few times. Right now its huge as there is the biggest push for aerospace in decades. All these uni's are trying to snatch up all that grant money so they can muck around and have little to show for it, but they got to play for a few years.

Unfortunately for us, Tripoli is the easy access means for lots of these groups. That places us in a bad spot but also puts us in a potential conflict of interest.

 

[AlexBruccoleri]

Unfortunately for us, Tripoli is the easy access means for lots of these groups. That places us in a bad spot but also puts us in a potential conflict of interest.

Can you elaborate on that? I have heard a lot of similar concerns but would like to hear people's reasoning.

 

[jsdemar]

The BobClarking of TRF continues!

 

[RGClark]

Have you ever taken an ethics course?

Actually, the university teams are operating like that. Remember these are not for profit efforts. They are educational efforts.
It is these educational efforts I’m arguing can make advancements in science because of the sheer numbers of rockets that can be sent to space and even on interplanetary missions, even if only at payloads at 1 kg size.(There are over 30,000 universities and colleges in the world.)

Bob Clark

 

[RGClark]

The BobClarking of TRF continues!

Definition:

To be “bobclarked”: to be led to a surprising and unexpected or even counterintuitive conclusion by force of logic alone.

Bob Clark

 

[boatgeek]

Actually, the university teams are operating like that. Remember these are not for profit efforts. They are education efforts.
It is these educational efforts I’m arguing can make advancements in science because of the sheer numbers of rockets that can be sent to space and even on interplanetary missions, even if only at payloads at 1 kg.(There are over 30,000 universities and colleges in the world.)

Bob Clark

I thought we'd already established that solids to orbit (let alone interplanetary!) on consumer-scale motors was completely infeasible.

The notion that university teams are up to/have the budget for casting 1500 kg+ of propellant is ... interesting. Not to mention designing and testing those motors, developing controls, etc. etc. Maybe if a professor was managing the project and providing continuity, but it's really hard to sustain 5-10 year projects at universities.

 

[StreuB1]

Actually, the university teams are operating like that. Remember these are not for profit efforts. They are educational efforts.
It is these educational efforts I’m arguing can make advancements in science because of the sheer numbers of rockets that can be sent to space and even on interplanetary missions, even if only at payloads at 1 kg size.(There are over 30,000 universities and colleges in the world.)

Bob Clark

Is your name secretly Randa or Roderick?

 

[prfesser]

Why bother with Earth orbit? Let's work out a trip to the Moon with commercial hobby-type motors! Let's see......26,240 Aerotech O5280 DMS motors......gotta be either single-use or DMS as it'll be tough to get 26,239 sets of 98mm hardware. (I have one set so I got that going for me.) And for the second stage....
.
.
.
...Okay, now for the fifteenth stage........

 

[Adrian A]

In which I attempt to show through math that the proposed rocket in #1 doesn't do the job of getting to orbit. This was mainly for my own interest--I don't really expect it to change the OP's mind. But hey, math and spreadsheets--it's like candy for an engineer.
Starting with some extremely rash assumptions (never make assumptions about rashes!):
0.5 kg payload
0.5 kg nose cone, roll control system, and guidance computer
0.8 mass fraction for motors
Thrust vector control mass 0.5kg for Stage 4, 1 kg for Stage 3, 2 kg for Stages 1 & 2
ISP ~225s (matches the CTI O8000)
Thrust is constant, propellant mass burn rate is constant (this mainly just makes the math easier)

Note that these assumptions are extremely optimistic. I would be absolutely shocked if they are possible except possibly increasing the specific impulse.

My process was to work backwards. When Stage 4 burns out, you want to have reached 7800 m/s. You enter the propellant mass and the impulse (plus an assumed time, which doesn't really matter), you get starting and ending acceleration based on your loaded and burned out mass, you integrate the acceleration, and you get delta V. That gets you your desired starting velocity to reach that ending velocity. Then you wash, rinse, repeat with each stage below. The end result is the rocket you would have to loft to ~200 km, turn horizontal, and start firing to make it to orbit.

So here's how that shakes out:
Stage 4: Full O motor, 41000 N-s, delta V 1850 m/s
Stage 3: Full Q motor, 160000 N-s, delta V 2500 m/s
Stage 2: Full S motor, 640000 N-s, delta V 2300 m/s
Stage 1: 50% V motor, 890000 N-s, delta V 1150 m/s

The astute reader will notice that you need to loft 1730 kN-s worth of impulse to orbital altitude just to get from "standstill at that altitude" to "orbit at that altitude". That whole stack weighs just a hair over 1000 kg, so it seems fairly plausible given the mass and payload capacity of the Lambda 4S. Also note that this is far, far beyond the capabilities of any amateur rocket builder.

QED.

If the TVC in the final stage moves the upper part of the whole upper stage around, it might be the only TVC you need for the whole stack. Not sure if that changes the answer much though. Using the rocket equation you don't even need to do the integration yourself.

Attached is my spreadsheet for this.

It includes just pure delta-V, no gravity losses or aerodynamic drag losses. This could be relevant for the thought experiment of whether it's possible to get an amateur rocket orbit if it starts start as a payload on Up Aerospace's suborbital sounding rocket. They say they are planning to do an all-solid orbit vehicle, by the way. Their payload to 115 km altitude is 55 kg. The spreadsheet shows how a rocket could get to orbit from there if it is doing all the horizontal delta-V and has some pretty aggressive assumptions to keep the mass down. With 80% motor mass fraction, minimal additional mass for control and staging and 250 vacuum Isp, a 4-stage rocket that finishes with an I motor could get to 7600 m/sec with a total mass of 47 Kg.

 

[StreuB1]

Why bother with Earth orbit? Let's work out a trip to the Moon with commercial hobby-type motors! Let's see......26,240 Aerotech O5280 DMS motors......gotta be either single-use or DMS as it'll be tough to get 26,239 sets of 98mm hardware. (I have one set so I got that going for me.) And for the second stage....
.
.
.
...Okay, now for the fifteenth stage........

 

[AlexBruccoleri]

I applaud Bob for posting a thought provoking thread. While I agree with a lot of the "cold water" posts, I like this type of thread. It is worth noting some university rocket teams have unreal levels of technical skill. Check out Boston University's rocket team. http://burpg.org/all-projects

I am actually curious how BU is making this happen. Maintaining that level of continuity among staff is not easy.

 

[jsdemar]

Definition:

To be “bobclarked”: to be led to a surprising and unexpected or even counterintuitive conclusion by force of logic alone.

Bob Clark

I'm glad you are taking this all in stride, Bob! Hopefully, you're absorbing our "conclusions by force of logic" to help you be more realistic about your overly-optimistic propositions.

 

[wclaybaugh2]

If the TVC in the final stage moves the upper part of the whole upper stage around, it might be the only TVC you need for the whole stack. Not sure if that changes the answer much though. Using the rocket equation you don't even need to do the integration yourself.

Attached is my spreadsheet for this.

It includes just pure delta-V, no gravity losses or aerodynamic drag losses. This could be relevant for the thought experiment of whether it's possible to get an amateur rocket orbit if it starts start as a payload on Up Aerospace's suborbital sounding rocket. They say they are planning to do an all-solid orbit vehicle, by the way. Their payload to 115 km altitude is 55 kg. The spreadsheet shows how a rocket could get to orbit from there if it is doing all the horizontal delta-V and has some pretty aggressive assumptions to keep the mass down. With 80% motor mass fraction, minimal additional mass for control and staging and 250 vacuum Isp, a 4-stage rocket that finishes with an I motor could get to 7600 m/sec with a total mass of 47 Kg.

Adrian:

A couple of quibbles:

The Up Aerospace rocket is a fully professional vehicle purchased from Cesaroni Aerospace; it is not an amateur motor and it costs far north of $10K.

The orbital effort is being funded--in part--by NASA Marshall and is neither "amateur" nor "low cost".

Bill

 

[Adrian A]

Adrian:

A couple of quibbles:

The Up Aerospace rocket is a fully professional vehicle purchased from Cesaroni Aerospace; it is not an amateur motor and it costs far north of $10K.

The orbital effort is being funded--in part--by NASA Marshall and is neither "amateur" nor "low cost".

Bill

I don't disagree with any of that. It's just a way to calibrate my sense of scale. We have seen successful amateur rockets take near-zero payload to the Von Karman line. The spreadsheet is trying to answer the question of, if your rocket starts out from there, what would it take to get the delta-V to orbit? It's fun to think it might not take more than a 50 kg rocket. And the Up Aerospace rocket is a nice data point for seeing what it would take to get 50 kg from the ground up to that starting point.

 

[Grog6]

I watched a new engineer build a 100,000V power supply back in the 90's. I watched with amusement, due to the lack of appreciation for the effort. After repeated failures, he finally gave up after about 6 good months of effort. After he gave up, one of the company owners and I put it inside a 40- foot long vacuum tank, pumped it down for a week, and the power supply worked the first time. Air is nowhere near what you think it is, lol.We did some fusion experiments we wanted to try that came out of the cold fusion stuff; we proved that of you use enough power, you can fuse duterium, lol. IDK what the engineer wanted to do; I don't think we ever told him the PS worked, thinking back. He also had no appreciation of how hard it was to count single electrons; I could do 20 per second, but that was it. He never got the difference between counting ions over electrons.

 

[AcadiaRockets]

this is what it took another private party to get a rocket to orbit this week.
https://www.space.com/china-kuaizho...YzP-hDzc9wqi-tbWZPy8xNJgxz6Yqbdx80HjMSjaONXrU

 

[Tim51]

I think the "bot" named Bob Clark needs to get out from behind the desk and actually build and fly a rocket.

This. Any RGClark thread on TRF is never more than the 'spectacle' of a bunch of very talented, very experienced, very knowledgeable rocketeers who've achieved amazing feats, patiently explaining basic reality to one bloke who fails to offer any evidence of ever having flown anything.

 

[AlexBruccoleri]

This forum should have a "Theory and Hypothetical Section" for topics like this. This is not a bad topic to discuss, but I feel like it needs a section. I also have posted some "out there" ideas, and a section for that would be appropriate.

 

[rocket_troy]

If the TVC in the final stage moves the upper part of the whole upper stage around, it might be the only TVC you need for the whole stack. Not sure if that changes the answer much though. Using the rocket equation you don't even need to do the integration yourself.

Attached is my spreadsheet for this.

Hi Adrian,
Don't take this as gospel, but I would be sceptical about amateurs achieving both that mass fraction and Isp for the 1st stage in particular. As I mentioned previously in the thread, it should be easier to achieve both as you move up in stage count though.
I'm also a touch sceptical about your mass allowance for control systems earlier in the thread, but I can't claim any expertise with that and I'd be delighted to be convinced otherwise
Also, there needs to be an allowance for stage coupling even for 1st-order analysis IMHO.

Anyway, hats off for the contribution,

TP

 

[neil_w]

ChatGPT weighs in.

 

[Tim51]

This forum should have a "Theory and Hypothetical Section" for topics like this. This is not a bad topic to discuss, but I feel like it needs a section. I also have posted some "out there" ideas, and a section for that would be appropriate.

I agree that would be an interesting section for TRF, but discussing 'out there ideas' that are based on at least some shared experiential knowledge or empirical data related to practical rocketry would make for a more useful and relevant discussion than what we're getting from the OP's supposed use of "the force of logic alone".

 

[RGClark]

If the TVC in the final stage moves the upper part of the whole upper stage around, it might be the only TVC you need for the whole stack. Not sure if that changes the answer much though. Using the rocket equation you don't even need to do the integration yourself.

Attached is my spreadsheet for this.

It includes just pure delta-V, no gravity losses or aerodynamic drag losses. This could be relevant for the thought experiment of whether it's possible to get an amateur rocket orbit if it starts start as a payload on Up Aerospace's suborbital sounding rocket. They say they are planning to do an all-solid orbit vehicle, by the way. Their payload to 115 km altitude is 55 kg. The spreadsheet shows how a rocket could get to orbit from there if it is doing all the horizontal delta-V and has some pretty aggressive assumptions to keep the mass down. With 80% motor mass fraction, minimal additional mass for control and staging and 250 vacuum Isp, a 4-stage rocket that finishes with an I motor could get to 7600 m/sec with a total mass of 47 Kg.

Thanks. What’s the final payload that reaches orbit?

Bob Clark

 

[RGClark]

Is your name secretly Randa or Roderick?

???

Like Sheldon on “The Big Bang Theory” I have been accused of being irony impaired. Can’t tell if that is a serious question or not. ”Bob” is a well-known nickname for Robert.

Robert Clark

 

[Adrian A]

Thanks. What’s the final payload that reaches orbit?

Bob Clark

None, unless a few grams happen to be left over.

 

[Alan15578]

Why bother with Earth orbit? Let's work out a trip to the Moon with commercial hobby-type motors! Let's see......26,240 Aerotech O5280 DMS motors......gotta be either single-use or DMS as it'll be tough to get 26,239 sets of 98mm hardware. (I have one set so I got that going for me.) And for the second stage....
.
.
.
...Okay, now for the fifteenth stage........

So, OTRAG with expensive solids instead of cheap pressure fed liquids?

 

[RGClark]

None, unless a few grams happen to be left over.

Commercial solid rockets commonly get 280+s vacuum Isp:



But for a particular propellant combination, vacuum Isp is largely a matter of nozzle size. So for the upper stages we can get higher vacuum Isp for our motors using longer nozzles. This will increase the payload possible.

This is why I wanted to find out using Openmotor or Burnsim what is the vacuum Isp of the Cesaroni motor used on the SpaceLoFt rocket:

Bob Clark

 

[plugger]

But you do have to construct the rockets without using airframes, i. e., no body tubes, since they add excessive weight. This requires skill at the advanced amateur level since you would need to use a fin can or directly attach the fins to the motor casing.

No you don't Bob, Adrian's post above mine directly refutes this made up rule.

 

[rocket_troy]

No you don't Bob, Adrian's post above mine directly refutes this made up rule.

If I was designing up an orbital capable vehicle (especially from solids), I certainly wouldn't consider anything not monocoque unless there was a really pressing case for it (no pun intended). Ditto for a Karman Line shot, although there's much more margin for "discretionary dry mass" with the latter.

TP