Active Flight Control

The Rocketry Forum

Help Support The Rocketry Forum:

boatgeek

Well-Known Member
Joined
Dec 27, 2014
Messages
2,641
Reaction score
1,058
Why in the world would a gov agency use a non-gov definition (NFPA is private, not gov) when they have a gov issued definition (FAR 101)? This seems very backwards to me.

22 CFR 121.1 references NFPA quite a lot actually. Did you know you can't export certified motors having more than 5 pounds of propellant? 22CFR 121.1(D) note 1 How does AT and CTI export anything M or larger?

And if your guidance system is not for export, does the state department's munitions export control list (22 CFR 121) even apply?
CFRs incorporate other regulations by reference all the time. They probably didn't use FAR 101 because Class 3 (P motors and above) is unlimited. There isn't a handy distinction in there between the very high end of our hobby (R? S?) and rockets intended to go 300km downrange. If they had used FAR 101, every rocket over O could be considered ITAR, and we wouldn't have threads here about those cool projects.
 

Richard Dierking

Well-Known Member
TRF Supporter
Joined
Nov 25, 2018
Messages
188
Reaction score
94
Location
Temecula, CA
Joe, are you just not admitting that you are a lawyer? "Exception to the exception" sure sounds like lawyer-talk to me. ;-)

I think there needs to be some well thought-out rules/codes about what's allowed. Like in that NFPA revision coming up. Somebody is going to do some foolish thing (hum, what have we seen, what could that be) and we would probably end up with a poorly written knee-jerk regulation that will severely limit our development in this hobby. At least if we had something concise on the books, when someone does something stupid, we could point to the code and say we already knew that was wrong; so, no reason creating some new regulation.
 

Steve Shannon

Well-Known Member
TRF Supporter
Joined
Jul 23, 2011
Messages
6,303
Reaction score
2,849
Location
Butte, Montana
I would bet (though not much money) that this note was added as part of a rulemaking comment process. I'm thinking the State Dept put out a Notice of Proposed Rulemaking with changes to the Munitions List, and someone at a hobby rocketry company noticed. They then put in a comment asking State to clarify that they didn't intend to regulate our hobby. State agreed, and threw in the note. The "active controls" line was probably someone either at State or the rocketry company worked up to try to clarify the NAR Safety Code "no guidance" rule to allow things like George's sun guidance or Jim Jarvis' vertical guidance systems.

Incidentally, does NFPA 1122 have anything about guidance? I think I saw that NFPA 1122 was up for revision before too long. This would be an excellent time to get some clarifying language into the governing regulations.
NFPA 1122 says nothing about guidance. Same for 1127.
 

boatgeek

Well-Known Member
Joined
Dec 27, 2014
Messages
2,641
Reaction score
1,058
NFPA 1122 says nothing about guidance. Same for 1127.
Is that something that NFPA would be willing to add/something that TRA would want to get into? As discussed as nauseum in this and other threads, it would be really nice to have some guardrails that are written down as opposed to extrapolated from the NAR and TRA Safety Codes.
 

Steve Shannon

Well-Known Member
TRF Supporter
Joined
Jul 23, 2011
Messages
6,303
Reaction score
2,849
Location
Butte, Montana
Is that something that NFPA would be willing to add/something that TRA would want to get into? As discussed as nauseum in this and other threads, it would be really nice to have some guardrails that are written down as opposed to extrapolated from the NAR and TRA Safety Codes.
Probably not; most regulators don’t comment on non-regulated activities. Simply state the regulations. If something isn’t regulated you don’t include a statement to that effect. It would be confusing and possibly in conflict with other regulations.
It’s simple. If something isn’t mentioned in regulations it’s not regulated.
 

Richard Dierking

Well-Known Member
TRF Supporter
Joined
Nov 25, 2018
Messages
188
Reaction score
94
Location
Temecula, CA
So, more than a week past without any additional posts.
I'm a bit disappointed about Steve's last comment. But, on the other hand, I understand his position on this. It might be a good idea to keep our "ear to the ground." Or, would that be the sky?
There is that nagging note in 22 CFR 121.1, but I'm not going to loose any sleep on that one! All my questions answered.
I"ll post something separate about my little project. To be honest, I know what I would like to do and don't currently know how I'm going to get there. Just going to plug away. I will be focusing my efforts on control of direction, like straight up! Start by leaning rocket away from the flight line, then at some point, rolling the rocket as necessary, and pitching it up and trying to keep it straight up to apogee. All, with two control surfaces. Perhaps someday I will try to use GPS, but I want to wait and watch a bit before thinking about doing that.
 

Steve Shannon

Well-Known Member
TRF Supporter
Joined
Jul 23, 2011
Messages
6,303
Reaction score
2,849
Location
Butte, Montana
So, more than a week past without any additional posts.
I'm a bit disappointed about Steve's last comment. But, on the other hand, I understand his position on this. It might be a good idea to keep our "ear to the ground." Or, would that be the sky?
There is that nagging note in 22 CFR 121.1, but I'm not going to loose any sleep on that one! All my questions answered.
Snip…
I understand your disappointment. I’ll try to explain the logic.
Regulations or rules are either prohibitive or inclusive but logically cannot be both, at least not easily. Although it’s not a legal regulation an example of an inclusive rule is the Tripoli Research Safety Code rule that inclusively lists which sugars may be used as the primary fuel in sugar motors. Because we list which ones may be used, no others may be used as the primary sugar fuel. That’s very straightforward. If we chose to use a prohibitive rule and list which ones were prohibited, any sugar not listed could be used, which was what we tried to prevent.
That also demonstrates that an inclusive list type rule is actually more restrictive and really only effective when there is a single rule maker. But it leaves a much greater opportunity for confusion whenever multiple regulators exist and more importantly it leads to much less freedom because it requires that the rule maker must approve everything.
Prohibitive rules work much more narrowly by only listing those things which are prohibited. That’s really how we should want regulations to work. That’s how most of the NFPA rocketry regulations work. Attempts to clarify a prohibitive rule by adding inclusive language simply creates confusion.
For instance, if we make a rule that prohibits blue rockets and then add a rule that permits red rockets, every other color has a question mark attached.
 

jqavins

Joseph Avins
TRF Supporter
Joined
Sep 29, 2011
Messages
3,374
Reaction score
1,037
Location
Howard, NY
That example suggests possibilitites like my exception interpretation from a few posts back. Blue rockets are prohibited, (implying that all other colors are allowed). A clarification is added that violet is not, under this regulation, considered blue, and is therefore not prohibited. So far so good. Then comes the exception to the exception: pale violet, which may also be called lavender, is considered blue and is therefore prohibited. When laid out step by step it's understandable, but it brings on confusion in practical terms.
 

Steve Shannon

Well-Known Member
TRF Supporter
Joined
Jul 23, 2011
Messages
6,303
Reaction score
2,849
Location
Butte, Montana
That example suggests possibilitites like my exception interpretation from a few posts back. Blue rockets are prohibited, (implying that all other colors are allowed). A clarification is added that violet is not, under this regulation, considered blue, and is therefore not prohibited. So far so good. Then comes the exception to the exception: pale violet, which may also be called lavender, is considered blue and is therefore prohibited. When laid out step by step it's understandable, but it brings on confusion in practical terms.
Exactly correct and why that exception to an exception (that’s how I interpreted it also) is terribly written.
 

boatgeek

Well-Known Member
Joined
Dec 27, 2014
Messages
2,641
Reaction score
1,058
Exactly correct and why that exception to an exception (that’s how I interpreted it also) is terribly written.
I think I saw above that NFPA doesn't have any regulations on guidance. That (to me anyway) indicates that the only restriction is from the NAR and TRA safety codes. That's assuming that guidance on our rockets doesn't go to the Munitions List because our range is less than 300 km from the launch point. Is that accurate?

If so, then either TRA or NAR (or both) could issue position papers on what they consider acceptable under the safety codes, which can be updated as technology evolves. This process would be much like the requirements to use electronic deployment for VMax motors or what switch arrangements for altimeters effectively inhibit charge firing. Something like that would be really helpful--it's not a regulation, it's policy for use of NAR/TRA safety codes and it would eliminate these arguments that pop up every single year.
 

Steve Shannon

Well-Known Member
TRF Supporter
Joined
Jul 23, 2011
Messages
6,303
Reaction score
2,849
Location
Butte, Montana
I think I saw above that NFPA doesn't have any regulations on guidance. That (to me anyway) indicates that the only restriction is from the NAR and TRA safety codes. That's assuming that guidance on our rockets doesn't go to the Munitions List because our range is less than 300 km from the launch point. Is that accurate?

If so, then either TRA or NAR (or both) could issue position papers on what they consider acceptable under the safety codes, which can be updated as technology evolves. This process would be much like the requirements to use electronic deployment for VMax motors or what switch arrangements for altimeters effectively inhibit charge firing. Something like that would be really helpful--it's not a regulation, it's policy for use of NAR/TRA safety codes and it would eliminate these arguments that pop up every single year.
It’s clear from NFPA and our organizations’ collective safety codes that launching against targets is forbidden. Federal law prohibits targeting aircraft in any way. I’m not sure what else to tell you or why you’re having a problem understanding that what’s left is permitted but you need to use common sense. Most simply put, don’t be stupid and don’t make something that could be mistaken for a weapon or that brings the scrutiny of the federal agencies who could seek to regulate us out of existence. This has been explained here and other places many times but people keep insisting on having a bright line drawn. Bright lines are regulations. Regulations are almost always reactions to people doing stupid things.
 

boatgeek

Well-Known Member
Joined
Dec 27, 2014
Messages
2,641
Reaction score
1,058
It’s clear from NFPA and our organizations’ collective safety codes that launching against targets is forbidden. Federal law prohibits targeting aircraft in any way. I’m not sure what else to tell you or why you’re having a problem understanding that what’s left is permitted but you need to use common sense. Most simply put, don’t be stupid and don’t make something that could be mistaken for a weapon or that brings the scrutiny of the federal agencies who could seek to regulate us out of existence. This has been explained here and other places many times but people keep insisting on having a bright line drawn. Bright lines are regulations. Regulations are almost always reactions to people doing stupid things.
I've pushed on this because this is the only item in the Safety Code that has regular questions about what the Code means and what is allowed. You can set your watch by the threads here asking about guidance, where different reasonably well-informed people will say that:
You can't aim at an aircraft or do something else that looks like a weapon
You can't do any kind of guidance ever
You can use guidance to aim the rocket vertical, but not at a point in the sky or over a point on the ground
You can use active guidance after a parachute has deployed (aka spot landings and the guided chute system Apogee is developing)
You can't do spot landings no matter what because that's aiming at a target even if the rocket recovers at a safe speed

I'm pretty sure all of these opinions have shown up in this thread, with real project examples of safe and unsafe guided rockets. To me, that indicates that the rule in the Safety Code needs to be updated or clarified. IMHO, it doesn't benefit anyone to have people dragging up regulations from the Munitions List because that's the only place that guided rockets are discussed. I definitely take your point that NFPA isn't an appropriate place to do that. It seemed to me that a very short statement from TRA and/or NAR giving general rules about what is allowed and what is not under their own Safety Codes would resolve most of these threads without getting any regulatory agencies involved. However, it's also clear that's not going to happen, so I'll bow out now and will stay out of future threads.
 

Steve Shannon

Well-Known Member
TRF Supporter
Joined
Jul 23, 2011
Messages
6,303
Reaction score
2,849
Location
Butte, Montana
I've pushed on this because this is the only item in the Safety Code that has regular questions about what the Code means and what is allowed. You can set your watch by the threads here asking about guidance, where different reasonably well-informed people will say that:
You can't aim at an aircraft or do something else that looks like a weapon
You can't do any kind of guidance ever
You can use guidance to aim the rocket vertical, but not at a point in the sky or over a point on the ground
You can use active guidance after a parachute has deployed (aka spot landings and the guided chute system Apogee is developing)
You can't do spot landings no matter what because that's aiming at a target even if the rocket recovers at a safe speed

I'm pretty sure all of these opinions have shown up in this thread, with real project examples of safe and unsafe guided rockets. To me, that indicates that the rule in the Safety Code needs to be updated or clarified. IMHO, it doesn't benefit anyone to have people dragging up regulations from the Munitions List because that's the only place that guided rockets are discussed. I definitely take your point that NFPA isn't an appropriate place to do that. It seemed to me that a very short statement from TRA and/or NAR giving general rules about what is allowed and what is not under their own Safety Codes would resolve most of these threads without getting any regulatory agencies involved. However, it's also clear that's not going to happen, so I'll bow out now and will stay out of future threads.
I respect you a ton. You’re a PE with a ton of experience including compliance. If you would like to suggest how to clarify this subject (not just that it needs more clarification) I will listen and sincerely consider your ideas.
 

boatgeek

Well-Known Member
Joined
Dec 27, 2014
Messages
2,641
Reaction score
1,058
I respect you a ton. You’re a PE with a ton of experience including compliance. If you would like to suggest how to clarify this subject (not just that it needs more clarification) I will listen and sincerely consider your ideas.
Thank you for the kind words. I will think about it a bit and send you some proposed language, either in this thread or via PM, whichever you prefer.
 

Richard Dierking

Well-Known Member
TRF Supporter
Joined
Nov 25, 2018
Messages
188
Reaction score
94
Location
Temecula, CA
No rule is going to be perfect. And, there will be exceptions. I think the most important thing is to encourage people to discuss their projects on RF, let officials at launches know well in advance of anything out of the ordinary, and for us to do our jobs keeping launches safe.

Steve can be firm, but he also knows the worst thing to do is not to listen.

Some people creating TVC systems are designing rockets that are not aerodynamically stable (e.g. CP-CG is 0 or close to it). So, when does the rocket reach a sufficient velocity to be stable? How about never. The rockets launch directly off their pad with no launch rod, rail, or tower. They don't lean their rockets away from themselves or spectators. For one of my projects, I don't even use a pad! Ironically, I wouldn't even use a blast deflector on the ground, but it's in the safety code.
What happens when people start landing their rockets under power? I've used retro rockets on my projects. But, no one will ever land a rocket under power. LOL

And, it would be a good thing to be able to direct your rocket during recovery and keep it in the established recovery area. Sometimes it's very difficult to do this with high alt projects, and even lower alts when the recovery area isn't large.

I know it doesn't seem logical to many people, but providing some guidance on what is allowed might actually encourage people to develop and test new flight control technologies. You know, here are the rules, now go for it!
 

Steve Shannon

Well-Known Member
TRF Supporter
Joined
Jul 23, 2011
Messages
6,303
Reaction score
2,849
Location
Butte, Montana
No rule is going to be perfect. And, there will be exceptions. I think the most important thing is to encourage people to discuss their projects on RF, let officials at launches know well in advance of anything out of the ordinary, and for us to do our jobs keeping launches safe.

Steve can be firm, but he also knows the worst thing to do is not to listen.

Some people creating TVC systems are designing rockets that are not aerodynamically stable (e.g. CP-CG is 0 or close to it). So, when does the rocket reach a sufficient velocity to be stable? How about never. The rockets launch directly off their pad with no launch rod, rail, or tower. They don't lean their rockets away from themselves or spectators. For one of my projects, I don't even use a pad! Ironically, I wouldn't even use a blast deflector on the ground, but it's in the safety code.
What happens when people start landing their rockets under power? I've used retro rockets on my projects. But, no one will ever land a rocket under power. LOL

And, it would be a good thing to be able to direct your rocket during recovery and keep it in the established recovery area. Sometimes it's very difficult to do this with high alt projects, and even lower alts when the recovery area isn't large.

I know it doesn't seem logical to many people, but providing some guidance on what is allowed might actually encourage people to develop and test new flight control technologies. You know, here are the rules, now go for it!
Thanks for the compliment. I do appreciate it.
Active systems have the potential to reduce our chances of flying outside of our authorized airspace. FAA appreciates that. But what we must be careful about making too easily available outside our community are technologies that could be misused as weapon delivery systems or for other criminal activities such as smuggling. I cringe at the thought of creating rules for this subject. Rules only limit the actions of people who care about following rules.
 

mikec

Well-Known Member
Joined
May 9, 2009
Messages
2,378
Reaction score
313
No rule is going to be perfect.
I'd frankly rather see no rule than a overly-constraining one-size-fits-all rule. As Einstein said in a different context, "everything should be as simple as possible, but no simpler."

No hobby TVC rocket is ever going to be so foolproof and reliable that it has no chance of being unstable. We already account for instability in conventional rockets with the impulse-based standoff distance. If those standoff distances aren't far enough to account for TVC, then move such a rocket out farther. That's what I've always done as an RSO when such things have come up. But if we were to define an exhaustive set of rules, where would that process stop?

If the hobby were full of actual TVC safety horror stories I would feel differently, but I'd prefer to avoid adding rules that address things that were only hypothetical problems.

As for misuse, that is a can of worms and a slippery slope you don't want to go down, because the banning of the hobby is at the bottom.
 

Titan II

Well-Known Member
Joined
Aug 24, 2013
Messages
839
Reaction score
93
I personally vote for leaving things as they are and support Steve's initial response. It is usually the same people that have issues with something like this, and recurrently want something done to their satisfaction. TRF is a small group of people, some more verbal than others, that do not necessarily represent the majority of those building and flying rockets. Remember the recent directive regarding switches? That issue would pale in comparison to this topic if it ever evolves to making rules.
 
Last edited:

DaveW6DPS

Well-Known Member
Joined
May 28, 2013
Messages
474
Reaction score
224
Location
Barstow, CA
And, I should have added that you are a good listener Steve.
Frankly, I don't know how you do it; following so many conversations and doing such a good job at it.
Especially given the twists and turns of this thread. I lost patience in the middle of page two. You remained reasonable throughout.

My compliments!
 

Steve Shannon

Well-Known Member
TRF Supporter
Joined
Jul 23, 2011
Messages
6,303
Reaction score
2,849
Location
Butte, Montana
Especially given the twists and turns of this thread. I lost patience in the middle of page two. You remained reasonable throughout.

My compliments!
If you mean me, I’m pretty sure I was cranky a couple times, but I really do appreciate your kindness and I apologize if my tone makes people give up.
 

boatgeek

Well-Known Member
Joined
Dec 27, 2014
Messages
2,641
Reaction score
1,058
This took a little longer than I anticipated, but here's a rough draft of guidance for guided flights. You will see that it includes a lot of "may" and "should consider" language rather than "shall". That's because I really didn't want to add new requirements, just make it clear that guidance is allowed and basic issues that the flyer and RSO should consider in their design. The only place that really deviates from the current safety code is an allowance for TVC rockets tohave a thrust:weight ratio below 3:1. I deliberately didn't address criminal activity (beyond targeting aircraft/objects/people) because that didn't seem likely. Arms developers have other places to look to develop weapons. Smugglers can use a large drone to move stuff a lot cheaper and less noticeably than via rocket.

Donning my flame-proof pants...

Guidance or attitude control of rockets in flight has the potential to improve safety, particularly by keeping rockets within the waiver cylinder. There are also reasonable concerns raised about safety of these types of systems. This policy describes some systems and gives guidance for flyers and RSOs. The guidance is not intended to be exclusive—systems not described here should be reviewed under the same principles.

The discussion below refers to the Tripoli Safety Code (TSC) and Tripoli Safe Launch Practices (SLP) documents.

No rocket may be flown with the intention of causing harm or injury to any person or object on the ground or in flight. This is the clear intention of SLP F.1 and K.2. All rockets must follow the TSC and SLP, including planning for safe recovery.

Guidance during boost and coast

Rockets may be guided during the boost and coast phases of flight, typically using either aerodynamic controls or thrust vector controls. Aerodynamic controls move fins or other control surfaces to guide the rocket, while thrust vector control moves the motor or exhaust plume to guide the rocket. Both systems could be used to guide the rocket along a vector (typically vertical) or toward a point in the sky. With either system, the guidance point/vector should be chosen to keep the rocket from flying over spectators and within the waiver cylinder at all times.

The flyer and RSO should consider failure modes of the guidance system. Failure of either type of system may result in an unstable flight or a flight in an unplanned direction. The flyer is completely responsible for the safe flight of the rocket and should consider failure modes and should mitigate them as much as possible to maintain a safe flight. The RSO may consider moving rockets with guidance systems to an increased standoff distance, particularly for unproven systems.

Rockets using aerodynamic controls should be aerodynamically stable with the control system inactive.

Rockets using thrust vector control do not depend on aerodynamic stability for a safe flight. Therefore, they do not need to follow the thrust:weight ratio requirements in SLP G.1, nor do they need to be aerodynamically stable in flight. The flyer and RSO should verify that the rocket has sufficient initial thrust to safely boost off of the launch pad. If the rocket is aerodynamically unstable, the airframe may experience high loads as it goes unstable at motor burnout. The flyer should estimate rocket speed at motor burnout and plan for safe recovery with the rocket unstable at that speed.

Guidance during recovery

Rockets may be guided to a landing point or zone while under a safe recovery system. The flyer should coordinate with the RSO to choose a safe landing area. The flight plan should keep the rocket over the closed range during flight and recovery. If an off-nominal boost results in the rocket flying over spectators, the guidance system should minimize the time the rocket is over spectators. Guided recovery systems may be more prone to tangling than standard parachute systems. The flyer should consider failure modes of the recovery system and ensure that the rocket will land at a safe speed.

Guided or unguided rockets may be flown so that they land as close as possible to a designated point (“spot landing”) provided that they meet all other requirements of the TSC and SLP and the landing point is in the closed range area.
 

mikec

Well-Known Member
Joined
May 9, 2009
Messages
2,378
Reaction score
313
Seems quite reasonable to me, as a guideline.

Rockets using aerodynamic controls should be aerodynamically stable with the control system inactive.
Suppose the control system fails and drives the control surfaces to some maximum unfavorable deflection? Does that have to be stable? That might be unreasonably constraining or at least hard to prove and favors TVC over aero control.

Maybe add "and surfaces at neutral"?
 

VernK

Member/Vendor
TRF Sponsor
TRF Supporter
Joined
Oct 1, 2014
Messages
118
Reaction score
53
Location
Boise, Idaho
... Rockets using thrust vector control do not depend on aerodynamic stability for a safe flight. Therefore, they do not need to follow the thrust:weight ratio requirements in SLP G.1, nor do they need to be aerodynamically stable in flight. The flyer and RSO should verify that the rocket has sufficient initial thrust to safely boost off of the launch pad. If the rocket is aerodynamically unstable, the airframe may experience high loads as it goes unstable at motor burnout. The flyer should estimate rocket speed at motor burnout and plan for safe recovery with the rocket unstable at that speed.
I don't know much about rockets with thrust vector control but shouldn't they be required to be aerodynamically stable AFTER motor burn out? So that they continue to fly in a controlled manner on up to apogee.
 

DaveW6DPS

Well-Known Member
Joined
May 28, 2013
Messages
474
Reaction score
224
Location
Barstow, CA
... The only place that really deviates from the current safety code is an allowance for TVC rockets tohave a thrust:weight ratio below 3:1...

...I deliberately didn't address criminal activity (beyond targeting aircraft/objects/people) because that didn't seem likely...

...No rocket may be flown with the intention of causing harm or injury to any person or object on the ground or in flight. This is the clear intention of SLP F.1 and K.2. All rockets must follow the TSC and SLP, including planning for safe recovery...

... Both systems could be used to guide the rocket along a vector (typically vertical) or toward a point in the sky. With either system, the guidance point/vector should be chosen to keep the rocket from flying over spectators and within the waiver cylinder at all times...

...Rockets using aerodynamic controls should be aerodynamically stable with the control system inactive.

Rockets using thrust vector control do not depend on aerodynamic stability for a safe flight...
Exactly how do you justify any change in the requirement for a 3 to 1 thrust ratio? Do you actually expect active control to be effective at very low thrust in all cases? This is incredibly non-conservative.

You say you don't address criminal activity, and later specifically address criminal activity.

You need to review your usage of "both systems" and "either system". Is it your intention to require both control surfaces and TVC? "Both systems can be used" but not one or the other?

Do rockets need to be aerodynamically stable or not?
 

boatgeek

Well-Known Member
Joined
Dec 27, 2014
Messages
2,641
Reaction score
1,058
I forgot to add two things above. First of all, the proposed policy starts immediately after the comment about the flameproof pants. Second, this is a spitball from Some Dude on the Internet(tm) in an attempt to head off the once-every-six-months argument on TRF about rocket guidance. For this to be actually used, it would need to be reviewed and adopted by TRA/NAR. Since Steve showed interest in it, it's written based on TRA rules, though it could just as easily be written for NAR. Naturally, I would expect that in that adoption process, there would be further discussion about the details. Even if I argue, I appreciate all input. That's part of having someone else check your work.

Seems quite reasonable to me, as a guideline.


Suppose the control system fails and drives the control surfaces to some maximum unfavorable deflection? Does that have to be stable? That might be unreasonably constraining or at least hard to prove and favors TVC over aero control.

Maybe add "and surfaces at neutral"?
That wouldn't hurt.

I don't know much about rockets with thrust vector control but shouldn't they be required to be aerodynamically stable AFTER motor burn out? So that they continue to fly in a controlled manner on up to apogee.
I have seen video of TVC rockets that were basically no fins plus nose cone. At burnout, they went unstable and hit apogee shortly thereafter. My understanding is that a big draw of TVC is that you can do much more accurate scale models that are truly unstable without TVC. Since those rockets have been demonstrated to fly safely, I don't want a suggested

Exactly how do you justify any change in the requirement for a 3 to 1 thrust ratio? Do you actually expect active control to be effective at very low thrust in all cases? This is incredibly non-conservative.

You say you don't address criminal activity, and later specifically address criminal activity.

You need to review your usage of "both systems" and "either system". Is it your intention to require both control surfaces and TVC? "Both systems can be used" but not one or the other?

Do rockets need to be aerodynamically stable or not?
Stability is addressed above. My understanding of the 3:1 requirement is that this was intended to assure adequate speed off the rail. Since that's much less of an issue in TVC, it didn't seem like it was necessary. It would be a good idea to talk with the people at BPS or people with a lot of TVC flight experience to see if there's a minimum thrust:weight needed for reasonable flight. In theory, there shouldn't be, but in theory there's no difference between theory and practice.

I assume that the comment about specifically addressing criminal activity was regarding aiming at [object/person]. I thought that was necessary because that's one of the first questions that comes up on this topic. There was a thread just recently here where someone wanted to design a system to hunt drones. In a prior post, Steve brought up questions or terrorism/smuggling. That was the kind of criminal activity that I didn't think I needed to bring up outside of my own introductory comment.

The both/either item is a good point. It should standardize on "either" if adopted to reduce confusion.
 

jderimig

Sponsor
TRF Sponsor
Joined
Jan 23, 2009
Messages
3,128
Reaction score
541
Excellent. Wondering if you could substitute another word for guided and guidance?
 

boatgeek

Well-Known Member
Joined
Dec 27, 2014
Messages
2,641
Reaction score
1,058
Excellent. Wondering if you could substitute another word for guided and guidance?
I thought about changing that, but I couldn't come up with something that sounded better. Flight control didn't really ring well with me, but might be the best other option. Suggestions would be welcome.
 

Latest posts

Top