Unexpectedly high RASAero estimate for a two-stage rocket.

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Wouldn't be fun if RGClark, Andrew_ASC, and nickcodybarrett were all at the same university?

Have you ever seen them in the same room? Maybe they are all the same person?
 
... No one here will be surprised if Princeton, USC, or other amateurs cross the Karman line, and no one is suddenly going to acquire a many-thousand dollar filament winder and a 60 quart mixer as a result. It has been done before (CSXT) and all that was shown is that the investment required was significant.

People say they won't be surprised by it. But if that were the case, there wouldn't be so much strenuous argument against it.
Crossing the Karman line by university teams or independent amateurs is important, because the natural progression after that is to do a fully orbital flight. But then the suborbital rocket can form the first, and largest, and most expensive, stage(s) of the orbital rocket.

Once the mindset is broken against it for the suborbital case, it will be recognized there really is no impediment to the fully orbital case either.

Bob Clark
 
People say they won't be surprised by it. But if that were the case, there wouldn't be so much strenuous argument against it.
Crossing the Karman line by university teams or independent amateurs is important, because the natural progression after that is to do a fully orbital flight. But then the suborbital rocket can form the the first, and largest, and most expensive, stage(s) of the orbital rocket.

Once the mindset is broken against it for the suborbital case, it will be recognized there really is no impediment to the fully orbital case either.

Bob Clark
Did you even read my previous post?
 
People say they won't be surprised by it. But if that were the case, there wouldn't be so much strenuous argument against it.
Crossing the Karman line by university teams or independent amateurs is important, because the natural progression after that is to do a fully orbital flight. But then the suborbital rocket can form the the first, and largest, and most expensive, stage(s) of the orbital rocket.

Once the mindset is broken against it for the suborbital case, it will be recognized there really is no impediment to the fully orbital case either.

Bob Clark
This is exactly the problem with your posts, the false equivalency you apply to things. People won't be surprised when universities succeed at suborbital flight, but not because it is easy as you suggest but because they have large budgets and access to facilities and laboratories that often rival major corporations. To say "if a university can do it, so can an amateur" is a false equivalency. A university succeeding at it therefore doesn't open any does to others to replicate they're results.

Also the rockets being designed by the universities are optimized for minimally sub orbital flights with little to no additional payload capacity and with no guidance. Which means they very likely would be unsuitable to launch a significant third stage on a trajectory appropriate for orbital flight. So again you have falsely equated their rockets to orbital boosters.

Also while the design and build of an orbital rocket is a progression from a successful suborbital flight it would be orders of magnitude more difficult in terms of cost and complexity. Therefore it is false to assume that a entity capable of achieving the former could then even attempt the latter.

The next step after a minimally suborbital flight soon the way to orbital flight is a suborbital booster with significant payload capacity and guidance to lift an orbital stage. These universities still have a lot farther to go than you seem to think.
 
Did you even read my previous post?

You're referring to the objection that I did not consider the mass of the payload that could be lofted to suborbital space for it to be used as a first stage of an orbital launcher.

We can make a comparison to the SpaceLoft XL
suborbital sounder rocket by UP Aerospace. It uses a Cesaroni made rocket motor with carbon fiber casing:

0

https://www.cesaroni.net/news.php

It's listed as carrying a 412 lbs propellant load. and 0.8 propellant fraction, so the total mass of the motor only would be 515 lbs, 234 kg. Now according to the UP Aerospace SpaceLoft XL payload guide, the total mass of their rocket with payload can be 354 kg:

SpaceLoft® XL Sub-Orbital Launch Vehicle.

The SpaceLoft® XL has an overall height of 6.1 meters, a
maximum diameter of 26.4 centimeters, and a maximum
lift-off weight (including payloads) of 354 kg in its
standard mission configuration.
https://www.upaerospace.com/custom-1/UPA PUG Lite R121214.pdf

So for the use as a first stage of an orbital launcher, the Cesaroni motor could loft, 354-234 = 120 kg to suborbital space. Take the required tangential delta-v for orbit as 7,400 m/s, once you subtract off the velocity you get for free from the Earth's rotation. For 3 additional stages, assume they also have a 0.8 propellant fraction, such as also using carbon fiber casing. Then I estimate you can get a payload of 2 kg to orbit, by the rocket equation.

The USC student rocket scheduled to launch in a week is to be a suborbital rocket about half-size to the Spaceloft rocket, and will also use carbon fiber casing. Then estimate the payload to orbit with three additional stages as ca. 1 kg.

By the way, this use of a suborbital rocket just to send the upper stages straight up to suborbital space really isn't the most efficient use of a first stage. Better would be to use the first stage to send the upper stages to high altitude but below space, and to impart high speed to the upper stages ca. 2,000 m/s.

But this architecture of using it
as a first stage in suborbital rocket type launch is just a proof of principle argument.

Bob Clark
 
You're referring to the objection that I did not consider the mass of the payload that could be lofted to suborbital space for it to be used as a first stage of an orbital launcher.

We can make a comparison to the SpaceLoft XL by UP Aerospace suborbital sounder rocket. It uses a Cesaroni made rocket motor with carbon fiber casing:


0

https://www.cesaroni.net/news.php

It's listed as carrying a 412 lbs propellant load. and 0.8 propellant fraction, so the total mass of the motor only would be 515 lbs, 234 kg. Now according to the UP Aerospace SpaceLoft XL payload guide, the total mass of their rocket with payload can be 354 kg:

SpaceLoft® XL Sub-Orbital Launch Vehicle.

The SpaceLoft® XL has an overall height of 6.1 meters, a
maximum diameter of 26.4 centimeters, and a maximum
lift-off weight (including payloads) of 354 kg in its
standard mission configuration.
https://www.upaerospace.com/custom-1/UPA PUG Lite R121214.pdf

So for the use as a first stage of an orbital launcher, the Cesaroni motor could loft, 354-234 = 120 kg to suborbital space. Take the required tangential delta-v for orbit as 7,400 m/s, once you subtract off the velocity you get for free from the Earth's rotation. For 3 additional stages, assume they also have a 0.8 propellant fraction, such as also using carbon fiber casing. Then I estimate you can get a payload of 2 kg to orbit, by the rocket equation.

The USC student rocket scheduled to launch in a week is to be a suborbital rocket about half-size to the Spaceloft rocket, and will also use carbon fiber casing. Then estimate the payload to orbit with three additional stages as ca. 1 kg.



Bob Clark

Did you actually read the first page of the PDF?

There is a chart of payload mass to altitude, right at the bottom of page 1. To the 115km nominal altitude you only have 40kg of payload space. That's only 700 g of payload by your math, and you haven't considered any control hardware. You will need attitude control (e.g. cold gas thrusters), because if you're not perfectly horizontal you'll burn up. And you'll need ignition control for all of your various stages, and you'll need to make it semi-rad-hardened and capable of working at extreme temperatures at either end of the scale. That's not going to be cheap or light. All without having it collapse under 14 G loads.

Show me a full-attitude-control rad/temp hard system under 24oz and I'll move on to the next issue. There's a reason spaceflight is expensive.
 
Does this thread remind anyone else of Monty Python's Argument Clinic?

[video=youtube;uLlv_aZjHXc]https://www.youtube.com/watch?v=uLlv_aZjHXc[/video]
 
Does this thread remind anyone else of Monty Python's Argument Clinic?
Not nearly that clever or entertaining.

OP added to ignore list and I'm not looking at this thread any more.
 
Not nearly that clever or entertaining.

OP added to ignore list and I'm not looking at this thread any more.

I only wish the ignore list was able to hide threads started by a given user, not just their posts. That would be a treat.

Back to "Karman line" AGAIN...
 
This thread now needs only one thing to take it to the next level- an appearance by he who shall not be named.
 
This blog on high power rocketry has discussions on using the N5800 to form a two-stage rocket to suborbital space:

Friday, October 28, 2011
Are two N motors enough for space?
https://highpowerrocketry.blogspot.com/2011/10/are-two-n-motors-enough-for-space.html


Tuesday, September 4, 2012
Bare Necessities: N5800 competition entry.
https://highpowerrocketry.blogspot.com/2012/09/bare-necessities-n5800-competition-entry.html

The second post above has links to discussions of the Bare Necessities minimum diameter single-stage rocket powered by the N5800. The blog author argues this would be a good design to base the two-stage suborbital rocket on.


Attached is my OpenRocket sim of a N5800 to N5800 suborbital space rocket. This shows the surprising sensitivity to the thickness of the fins to the altitude. At 1/4" thick the altitude comes to 120 km. But if it were possible to reduce the fin thickness to 1/16" it would sim to 197 km, an increase of 77 km(!)

Bob Clark
 

Attachments

  • N5800 to N5800- 3 fin.ork
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It is possible to reach space using a N to N staged rocket *if* you don't have the requirements that we as hobbyist have. We have a requirement to keep frangible metals to an absolute minimum. We have a requirement to fully recover all parts/stages. We have a requirement to meet FAA regulations. Nearly all of us have budget restrictions. Basically, if we could ignore all the requirements we have, it would be just as easy as these universities are finding it is. Not a walk in the park, but not limited to governments any more either.

As for your simulations, please keep in mind that simulations are not real world and you can't say something is 100% possible because it worked in the sim. Sims take shortcuts, sims have errors, sims make assumptions, sims are only as good as the data you feed them. Redo your sim with realistic data and see what your result is. Now add all the requirements that we have into that sim and see what happens. We as a hobby have come very far in the last decades but except for a few of us, we're still not quite there yet.
 
It is possible to reach space using a N to N staged rocket *if* you don't have the requirements that we as hobbyist have. We have a requirement to keep frangible metals to an absolute minimum. We have a requirement to fully recover all parts/stages. We have a requirement to meet FAA regulations. Nearly all of us have budget restrictions. Basically, if we could ignore all the requirements we have, it would be just as easy as these universities are finding it is. Not a walk in the park, but not limited to governments any more either.
As for your simulations, please keep in mind that simulations are not real world and you can't say something is 100% possible because it worked in the sim. Sims take shortcuts, sims have errors, sims make assumptions, sims are only as good as the data you feed them. Redo your sim with realistic data and see what your result is. Now add all the requirements that we have into that sim and see what happens. We as a hobby have come very far in the last decades but except for a few of us, we're still not quite there yet.

The SpaceLoft XL suborbital sounding rocket by UP Aerospace, Inc. is launched from Spaceport America in New Mexico. As with most rockets sent to suborbital or orbital space, the SpaceLoft XL rocket does not recover the rocket booster, though it does recover the payload section. Readers of this forum are familiar with the Spaceport America site as it is also where university competitions of rocket launches are often held.

I believe the Princeton team aiming for a suborbital space launch near the end of this month will also launch from Spaceport America. The Princeton team is very open to discussing the process towards getting to this point and also the technical details of their rocket. Amateurs interested in attempting a suborbital space launch and interested in the question of the necessity of recovering their boosters should be able to get useful information from them.

About the sims, I am just getting started using them. I would be interested to see what the results are for others who did sims for O8000-to-N1000, N5800-to-N1000, and N5800-to-N5800 rockets. For one thing I don't know what are the best designs for fins for rockets expected to reach supersonic speeds. Actually for reaching the Karman line, the needed speeds are hypersonic.


Bob Clark
 
Did you actually read the first page of the PDF?
There is a chart of payload mass to altitude, right at the bottom of page 1. To the 115km nominal altitude you only have 40kg of payload space. That's only 700 g of payload by your math, and you haven't considered any control hardware. You will need attitude control (e.g. cold gas thrusters), because if you're not perfectly horizontal you'll burn up. And you'll need ignition control for all of your various stages, and you'll need to make it semi-rad-hardened and capable of working at extreme temperatures at either end of the scale. That's not going to be cheap or light. All without having it collapse under 14 G loads.
Show me a full-attitude-control rad/temp hard system under 24oz and I'll move on to the next issue. There's a reason spaceflight is expensive.

From the appearance of the rocket quite a bit of mass is taken up by the other components of the bare rocket, i.e., with no payload, that does not include the motor. But with the booster used as the first stage of an orbital rocket, all this extra mass would be taken up by the upper stages, not just the payload of the SpaceLoft rocket.

Here's an image of the trajectory of the SpaceLoft rocket from the payload guide I linked to:

Space_Loft_trajectory.png


You see the booster is not recovered, but the payload section and nosecone are recovered by parachute. The motor is 10 feet long and the payload section and nozzle add to another 10 feet. So this would amount to a significant weight for the recovery system.

Here's an image of the nosecone:

UP+Aerospace.jpg

Environment Monitor, awaits installation and integration with the nose cone of UP Aerospace' SL-6 rocket. -NASA


I was surprised by the thickness of the walls of the nosecone. But you can see from the image of the trajectory, that the recovered portion comes down nose first. So probably the nosecone is built up to protect the payload carried in the nosecone. Then this would amount to significant weight for the aluminum nosecone. You can see also in this image the nosecone payload is placed on a thick metal bulkhead, also adding to the weight. Keep in mind too, for an orbital launcher for only cubesats at say 1 to 3 kg size, the nosecone itself would be much smaller.

This page in the payload guide describes the components holding the payloads in the nosecone and body of the rocket:

Space_Loft_PTS.png




The table at the bottom gives the total weight for the payload and their containers. This totals 43.5 kg when you consider there are 3 containers of the PTS4 type and 4 of the PTS10 type.

The fin can on the rocket appears to be aluminum also adding weight:

20140913__BZ14UPAEROSPACE14112p1.jpg



Finally here's an image of 4 men carrying the recovered portion of the rocket suggesting it has significant weight:

SL7-payload-recovery-UPaerospace.jpg



Bob Clark
 
USC’s Rocket Propulsion Lab just announced on their mailing list that they are postponing this weekends attempt at a suborbital space launch. They haven’t set a new date yet.

As far as I know the Princeton teams attempt at a suborbital space flight is still set for later this month.

Bob Clark
 
The SpaceLoft XL suborbital sounding rocket by UP Aerospace, Inc. is launched from Spaceport America in New Mexico. As with most rockets sent to suborbital or orbital space, the SpaceLoft XL rocket does not recover the rocket booster, though it does recover the payload section. Readers of this forum are familiar with the Spaceport America site as it is also where university competitions of rocket launches are often held.

I believe the Princeton team aiming for a suborbital space launch near the end of this month will also launch from Spaceport America. The Princeton team is very open to discussing the process towards getting to this point and also the technical details of their rocket. Amateurs interested in attempting a suborbital space launch and interested in the question of the necessity of recovering their boosters should be able to get useful information from them.

About the sims, I am just getting started using them. I would be interested to see what the results are for others who did sims for O8000-to-N1000, N5800-to-N1000, and N5800-to-N5800 rockets. For one thing I don't know what are the best designs for fins for rockets expected to reach supersonic speeds. Actually for reaching the Karman line, the needed speeds are hypersonic.


Bob Clark

You could always find one of the CTI P8000 motors...
 
You're referring to the objection that I did not consider the mass of the payload that could be lofted to suborbital space for it to be used as a first stage of an orbital launcher.

We can make a comparison to the SpaceLoft XL
suborbital sounder rocket by UP Aerospace. It uses a Cesaroni made rocket motor with carbon fiber casing:

0

https://www.cesaroni.net/news.php

It's listed as carrying a 412 lbs propellant load. and 0.8 propellant fraction, so the total mass of the motor only would be 515 lbs, 234 kg. Now according to the UP Aerospace SpaceLoft XL payload guide, the total mass of their rocket with payload can be 354 kg:

SpaceLoft® XL Sub-Orbital Launch Vehicle.

The SpaceLoft® XL has an overall height of 6.1 meters, a
maximum diameter of 26.4 centimeters, and a maximum
lift-off weight (including payloads) of 354 kg in its
standard mission configuration.
https://www.upaerospace.com/custom-1/UPA PUG Lite R121214.pdf

So for the use as a first stage of an orbital launcher, the Cesaroni motor could loft, 354-234 = 120 kg to suborbital space. Take the required tangential delta-v for orbit as 7,400 m/s, once you subtract off the velocity you get for free from the Earth's rotation. For 3 additional stages, assume they also have a 0.8 propellant fraction, such as also using carbon fiber casing. Then I estimate you can get a payload of 2 kg to orbit, by the rocket equation.
...

I'd like to get an independent estimate of the weight the SpaceLoft rocket's Cesaroni motor could loft to suborbital space. For instance, the phrase in the UP Aerospace payload guide of maximum lift-off weight of 354 kg in its standard mission configuration does not necessarily mean it could get that weight to the full 115 km. It could be to some lower altitude at that max weight. So I wanted to do a sim on the motor only.

This file gives the specs on the Cesaroni motor:


Product Data Sheet
Booster motor, Part# UPA-264-C
https://www.freelists.org/archives/roc-chat/01-2014/pdf0PNbprKh1r.pdf

However, this doesn't give the thrust data for the motor by which you could make a thrust data table for a RASP ENG file for input to OpenRocket or RASAero. But it does give a graph of the thrust:

Space_Loft_motor_thrust_curve.png


Then there is an app to turn a thrust graph to a thrust data table, described here:

https://www.thrustcurve.org/contribute.shtml


So I'll take a stab at making a RASP ENG file for the motor and then doing a OpenRocket and/or RASAero sim.

Bob Clark
 
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