altitude vs visibility

[bjphoenix]

I tend to like my rockets to stay in sight at apogee so I'm looking for ideas on how to gauge this. I have some data points for reference, I'm wondering how this extrapolates to other combinations.

One of my data points if an Estes HiFlier XL, I have one and there seem to be several others that show up at our launches. I've launched mine on D12 in good visibility when I could see it at apogee, this past Saturday I launched it under slightly cloudy conditions and could not see it at apogee. My Open Rocket sim says about 700 ft altitude with a D12. On that same day I launched an Executioner with E12 and it was well within visibility, for that combination Open Rocket predicts 830 ft.

So my question is does the visibility scale up linearly? The HiFlier XL is 1.6" diameter, would a 1" diameter rocket at 440 ft be barely visible? Or the 2.6" diameter Executioner at 1100 ft?

 

[mh9162013]

I think there are a lot of variables at play here, but I've read that, as a general rule, maximum visibility is 1,000 feet for every 1 inch in rocket diameter.

In my opinion and experience, that's probably a slightly optimistic rule of thumb. I probably don't have 20/20 vision, though.

 

[AdAstraPerAspera]

I came up with the same on my own, when I was younger, and had exceptionally good vision (better than 20/20). Thought it was conservative. Then my vision became more normal, and I started losing stuff in the sky....

 

[boatgeek]

I tend to like my rockets to stay in sight at apogee so I'm looking for ideas on how to gauge this. I have some data points for reference, I'm wondering how this extrapolates to other combinations.

One of my data points if an Estes HiFlier XL, I have one and there seem to be several others that show up at our launches. I've launched mine on D12 in good visibility when I could see it at apogee, this past Saturday I launched it under slightly cloudy conditions and could not see it at apogee. My Open Rocket sim says about 700 ft altitude with a D12. On that same day I launched an Executioner with E12 and it was well within visibility, for that combination Open Rocket predicts 830 ft.

So my question is does the visibility scale up linearly? The HiFlier XL is 1.6" diameter, would a 1" diameter rocket at 440 ft be barely visible? Or the 2.6" diameter Executioner at 1100 ft?

In my experience, visibility at altitude does scale pretty much linearly by tube diameter. I also use the 1"/1000 feet, but I'm also usually launching with a bunch of (relative) kids with good vision. ~10 years old is a good sweet spot between being responsible enough to track a rocket and not being so old they don't want to do anything you ask.

 

[afadeev]

I tend to like my rockets to stay in sight at apogee so I'm looking for ideas on how to gauge this.[...] So my question is does the visibility scale up linearly? The HiFlier XL is 1.6" diameter, would a 1" diameter rocket at 440 ft be barely visible? Or the 2.6" diameter Executioner at 1100 ft?

I don't find the visibility scaling to be all that linear, and cloud cover trumps all other considerations.
Rocket color and distraction levels on the ground play a part as well.

When I launch by myself, with clear blue sky, and I pay attention, I can see low-power rockets (1-2") upto ~2,500 feet. Ability to stay focused is required to follow them on the descent as much as half-decent eye sight. If I'm with friends or family, that limit is closer to 1,000-1,500 feet.

If the sky is somewhat cloudy and grey/milky, you will loose them sooner.
If there is even one (1) cloud somewhere on the horizon, the rocket is very likely to find its way into it.

The slower they descent, the more likely you are to loose them. So mark the bearing, and be prepared to find them in the sky again. The higher they went and the slower they decent, the more likely you are to look for them for the second/third time.

For high power rockets, multiply everything by 2.
Unless you have a tracker, in which case, you will never loose sight of your rocket, no matter how high it goes.

HTH,
a

 

[JimByrne]

The color of your rocket & parachute makes a big difference

 

[bjphoenix]

The color of your rocket & parachute makes a big difference

I was thinking more in terms of the rocket itself, before ejection. The rocket that I had trouble seeing last Saturday was red in front and black at the back half.
I'm much older than 20 years old, 1" per 1000 ft. doesn't work for me.
I was going to say in the original thread that another data point is an Estes Alpha on B6-4, I thought I remembered that they were barely visible. Then I did a sim and got 800+ ft for that combination. For the people who can see 1" per 1000 ft, this would be visible. I'll have to pay more attention at future launches to gain some more data points.

 

[Hobie1dog]

The color of your rocket & parachute makes a big difference

+1

 

[boatgeek]

Pointing at the rocket in the air also helps a lot, both in tracking it and finding it again after you've lost it.

 

[bjphoenix]

On a related question- does 700 ft sound right for a HiFlier XL on a D12? I did an internet search for a sim file and plugged it into OR, and that's what I got. I searched for an Estes Alpha sim and plugged in a B6 and got over 800 ft. We have a lot of people bring Alpha-sized rockets to our launches and they seem to stay visible on a B6. I never know if there is something hidden in an OR file that I download that could affect its performance. When I use such a sim to adapt to one of my own designs I go through all of the components carefully to see what they are but something I download just for a quick check I don't always take the time to do that.

At some of our big launches I've seen people bring binoculars. I wondered how that would work for spotting rockets at altitude. It seems to me that the narrow field of view would make it hard to find the rocket in the sky. Has anybody ever tried this? I also remember seeing photos in the old versions of Stine's book of optical tracking devices used to determine altitude and I wondered how well those would work. What we need is a little radar unit with screen that could set next to the launch controller.

 

[Tyeeking]

At some of our big launches I've seen people bring binoculars. I wondered how that would work for spotting rockets at altitude. It seems to me that the narrow field of view would make it hard to find the rocket in the sky. Has anybody ever tried this?

With practice I’ve become pretty good at tracking rockets with binos. The trick is to sit in a chair or on the ground in a comfortable manner that allows you to lean back. Don’t watch the initial launch from the binos but instead use them after motor burnout and simply begin at the smoke trail and follow it up to locate the rocket during coast. For safety purposes never follow a rocket with binos if it runs a chance of tracking with the sun in the background.

 

[ONAWHIM]

Tracking with binoculars is difficult instead look with your eyes and bring the binoculars into you vision path. Drop them down a bit to reaquire then bring them back up. Practice looking at aircraft.

And read the last sentence in @Tyeeking's post at least twice ^^^^

 

[bad_idea]

My eyes aren't what they once were, and it's only after getting back into rocketry after decades out that I've routinely tried to track rockets going over 1k'. I find that in most conditions I can track a rocket with a diameter of 1 arc minute or a little smaller. In good conditions, I can do a lot better, but there are no guarantees, so if I'm planning to fly past that 1 arc minute limit, I try to fly a tracker or at least a very reflective streamer.

Example:

BT-70 is 57mm in diameter. 57mm*60minutes*360 degrees/(2*pi)/1000 gives me a distance of 196m / 643' at which I can be fairly confident of tracking the rocket through apogee. In practice the limit's a bit beyond that, but 1 arc minute of the sky is a handy figure to remember.

Many of you will have much better eyes and a lot more experience tracking and should be able to do far better.

 

[techrat]

I tend to make my rockets BT-70 or bigger (3" and 4" are now common for me); exactly for that reason, I like to see the rocket all the way to apogee. Common size for a rocket for me these days is a 3" diameter, 3-foot tall rocket running on a F25 or higher motor and a 24" chute. Big Rocket, fair sized motor == good flight and easily recoverable.

 

[SolarYellow]

On a related question- does 700 ft sound right for a HiFlier XL on a D12?

Rough order of magnitude, that sounds about right.

 

[bjphoenix]

I find that in most conditions I can track a rocket with a diameter of 1 arc minute or a little smaller.

This sounds the same as what we call "1 minute of angle" which is 1" at 100 yards.

 

[bad_idea]

This sounds the same as what we call "1 minute of angle" which is 1" at 100 yards.

Yes, same thing. 1.047" per hundred yards.

Edit to add: my hobby thoughts and knowledge must be too compartmentalized. I hadn't drawn the association, though in years past I spent many an agonizing hour chasing sub-MOA groups.

 

[bjphoenix]

I've been working on this a bit more so I can get the next 2 builds in my mind underway.

I like BT60 size rockets but most of mine don't fly well on C6 motors (do a bit better on C5) but on D12 they fly too high for most of my launch conditions. So the logical next step is to a BT70 (2.2" diameter) tube which lowers the altitude a bit and increases the visibility. My other idea is to go to a BT80 with more motor which gets a bit higher but still has better visibility than a BT60 on a D12.

I haven't been able to get more data points to fine tune my rule of thumb but so far the rule says that 450 times diameter (inches) gives maximum comfortable altitude (ft). The 450 part is subject to change (450 ft per inch of diameter).

 

[SolarYellow]

Could also try C11 motors. Thrust similar to a D12 to get off the rod, but it burns out quickly and doesn't go that high.

 

[cwbullet]

I would always lean toward visible.