# mardlamock

Members

139

## Community Reputation

7 Neutral

• Rank
Spacecraft Engineer
1. ## Modeling a gravity turn - could you help me out with differential equations? ;)

Just do a 4 DoF simulation of the rocket launch with orbital mechanics and drag taken into account, subdivide gravity turn into say 100 steps and use a solver to get an estimate. Its not all that hard. When doing the actual numerical simulation you will have to split the diff equation as many times as needed in order to be able to even do it. Pop an excel sheet to do it first and it shouldnt take you longer than a couple of hours.
2. ## Designing Solid Fuel Rocket

Nakka is the place to go
3. ## Macross Missile Spam -> The only way to go

How accurately can a spacecraft hold its attitude? Wouldnt that also affect the range of a laser weapon due to the aiming being off? Lets assume the maximum error in aim is of around 4 meters. Current space telescopes can hold an attitude with 0.007 arsecs of accuracy, that gives us that the maximum engagement distance is of 83000 kilometers. Lets also say that the approach speed is of 6 kilometers per second, which is sort of reasonable considering the distance between colonies and the orbital mechanics associated (say a moon colony vs GEO colony). That gives us an engagement time of almost 4 hours, that doesnt seem too long actually. What do you guys think?
4. ## How Will SpaceX Actually Make Money?

What makes you think that? An old Atlas with modified engines could take a considerable payload into orbit. Besides, only having to use the same set of engines reduces costs a lot, if you look at the numbers, the motors take a really significant chunk of the total launch cost. The dry mass to payload ratio is also significantly lower for SSTO's than for regular multi stage vehicles, that means that for each kg of payload you need less rocket. - - - Updated - - - Yup, thats what I am talking about.
5. ## How Will SpaceX Actually Make Money?

Staging events are the most critical event in any rocket launch. Read this http://exoscientist.blogspot.com.ar/2013/11/the-coming-sstos-falcon-9-v11-first.html
6. ## How Will SpaceX Actually Make Money?

I for one agree with most of what you said. I think they should dump their current 2 stage model and go for a vertical takeoff SSTO using a modified falcon 9's first stage, the lowered complexity thanks to no staging events and only using one set of engines would lead to a significant decrease in prices. Maybe the could get reusability in that SSTO too, idk though.
7. ## Inflatable "space elevator"!

You are forgetting about the tyranny of the rocket equation people, the delta v used to compensate for gravity losses equates to a lot of propellant and a much larger vehicle overall.
8. ## Rocket coupling and staging

Use nose blown recovery.
9. ## Excess speed to height

Hi everyone! So, I ve been thinking about how high a plane can climb given an initial airspeed and a minimum airspeed. I first thought it was a simple matter of potential+kinetic energy remaining equal throughout the flight, but then I brain farted and now I dont really know what to think. If the only forces acting on the aircraft were gravity and drag, then the final mechanical energy would be always less than the initial, but that is never true because we also have lift. When you add lift into the equations, the rate at which you lose energy diminishes considerably, if you are ascending at a constant rate that is. This is because the vertical lift force cancels the weight of the aircraft, and the resulting energy losses are only due to drag and the horizontal lift force component. Example: a plane is going at 200m/s, it performs a climb until it reaches 180m/s at a constant ascent rate of 5m/s. Without lift or drag the maximum height the plane coud reach would be 20m (1/2*20^2=g*h). Assuming that the angle with respect to the surface of the earth is small then the horizontal lift force component is negligible. In order for the final energy to be less than the initial energy, the acceleration due to drag has to be more than 5 m/s^2. But what if it isnt? Lets say instead of it being 5m/s^2 its 4m/s^2, then, the plane will take 5 seconds to lose the 20m/s we were willing to convert into height. And as we said before, the climb rate remained constant at 5m/s, which means that the height will increase by of 25m. The thing is that, if it increased to 25 m then the system has more mechanical energy than at the start of the climb. So, what am i missing here? I have seriously got no idea where the extra energy comes from and wether its actually available for use. Anyways, thanks for reading so far! Please reply and tell me what you think!
10. ## [Philosophy] Value

You guys need some Subjective theory of value here. http://en.wikipedia.org/wiki/Subjective_theory_of_value.
11. ## The Next "SpaceX"?

I think there is potential for a next spacex, but it would have to be in India or some cheap ass place. Massively manufactured modular rockets, with cheap indian labour. Thats how electronics became so cheap people. OUTSOURCING!!!
12. ## Burials Galore [How do you want to be buried]

I would like to be Cryopreserved and launched into space, that way I can avoid natural disasters whilst still having the small chance of being revived.