Orbital space is 25 times harder than suborbital

OverTheTop

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plugger

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Correct, but the earlier ones used gravity turn. My comment still stands. The final payload stage achieved correct orbit, as I stated, with an IMU and RCS, as you stated. It depends on how accurate you need the orbit.

Edge case anyway, don't get too hung up on it ;) .

Earlier ones weren't orbital rockets. The Lambda-4S was the first orbital rocket out of the series, and it had active guidance. From the link you shared there's a Scott Manley video on this family of rockets, within it he states the following.

and the compromise was to have no guidance on the rocket until absolutely necessary to get it into orbit.

lambda-4s.png lambda-4s-ascent.png
 

Loki Research

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Mike: I won't speak for Scott but I can observe that the aluminum tube in my 6" by 60" vehicle is about 13.4 lbsm. If I were to directly substitute carbon fiber (which is a bit less than half the density of aluminum) then a "black aluminum" tube of the same 0.125" wall would come in at a bit over 6.6 lbsm. This would result in the stage propellant fraction going from around 0.59 to about 0.64.

Simulation indicates that would change the ground launch performance from about 75 k feet to about 80K feet, payload included....

Bill
On the last version, I used a 50" AT style case made from extruded 6061T-6511.
I don't have this case weight on hand, but the new, stronger DOM 6061-T6 tubing I ordered is 1.717 lb/ft.
Using the new tubing weight, if you could remove 50% of that weight over 48", leave 1" at each end of a 50" case and add 1/2 the weight removed back in CF, you'd have a case weight of about 5.437 lbs or 2,466.3g and the removal of roughly 1 foot worth of tubing in weight, 1.717lbs. Neat math trick.

Similar to what Bill stated, this would bring me from about 62.45% to 65.57%. Half the % increase of his theoretical full CF case so this makes sense to me.

I have zero idea what the cost to do this would be, however I may be hard pressed to find a customer in this market willing to pay this cost beyond what a 52" reusable O motor hardware would cost. Now if this were the 72" version, it may be more worth it for someone doing a 2-stage space flight with these paired together.. I have the tubing if someone wants to find out. ;-) The real question is whether or not it could be made for less than what a T6-2024 would cost. Last I checked it was about 30% more than the same wall thickness in 6061 but was 1.753 lb/ft.
 

RGClark

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No, not a must. Not wrong and not mainstream, but orbit without guidance is achievable. There is a Japanese launch vehicle that achieves orbit, without guidance, by setting a launch angle and using the gravity turn to determine the final orbit at burnout. I suspect the actual tolerances on the orbit would be a bit wide and probably need finessing with the payload stage if a more particularly accurate orbit was a requirement.

Thanks for the informative response.

Bob Clark
 

RGClark

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Earlier ones weren't orbital rockets. The Lambda-4S was the first orbital rocket out of the series, and it had active guidance. From the link you shared there's a Scott Manley video on this family of rockets, within it he states the following.



View attachment 550032 View attachment 550033


Thanks for the image of the Lambda 4S trajectory. Openrocket and RasAero can’t do orbital trajectory sims because they can’t model first launching vertically, then doing a pitch over to a specified angle at a specified altitude.

However, they can model launching at a specified angle to begin with. This is not the most efficient approach to reaching orbit but it can work. Quite useful then is knowing an effective launch angle to use. Also useful is knowing the stage separation times and ignition delays to use.


Bob Clark
 
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