Anybody know anything about rocketry?

[josh817]

Alright so... senior design project is to reverse engineer the X-15 and then make it carry passengers for a suborbital and orbital mission. Right now we're working on suborbital. I am doing the propulsion systems.

 

We know the aircraft was powered by a liquid fueled rocket which coul be throttled from 30%-100% by varying the flow of hydrogen peroxide to the turbopumps (thus changing the pump speed rather than regulating the fuel flow). We also know that 10% of the thrust was used to overcome drag, 20% to overcome gravity, leaving 70% to accelerate.

 

This directly translates into delta-Velocity. So, for one of their high altitude missions, the X-15 was airlifted to 45000 ft @ 790 ft/s. The rocket ignited and it accelerated for 84.5 seconds until burn out where it was travelling at 5380 ft/s @ 176000 ft. The aircraft continued to climb until it reached ~360000 ft @ 4150 ft/s, and then it began a reentry phase.

 

SO...

Knowing this, we would like to remove test equipment and add people. We're looking at a max of ~400 lbs addition. Am I wrong in thinking that we would still be able to achieve 360000 ft using the same engine, despite the additional losses due to overcoming increased gravity (weight)? We're going to look at thrust required vs thrust available due to mach divergence at M=1, but I'm still figuring we have far more power than needed.

 

• Part of me says well with 60000 lbs of thrust going 100% throttle for the full burn, they reached 360000 ft. Adding more weight will result in less performance. Reducing thrust will result in less performance.
• Another part of me says well... we are outside of useable atmosphere (no stall now), so why the hell do we feel the need to go 4150 ft/s at apogee? Instead of wasting fuel towards massive acceleration, can we reduce the throttle (decrease mass flow rate), extend burn time, go slower but reach the same or higher altitude?

Edited November 19, 2014 by josh817

[TimZ]

Alright so... senior design project is to reverse engineer the X-15 and then make it carry passengers for a suborbital and orbital mission. Right now we're working on suborbital. I am doing the propulsion systems.

 

We know the aircraft was powered by a liquid fueled rocket which coul be throttled from 30%-100% by varying the flow of hydrogen peroxide to the turbopumps (thus changing the pump speed rather than regulating the fuel flow). We also know that 10% of the thrust was used to overcome drag, 20% to overcome gravity, leaving 70% to accelerate.

 

This directly translates into delta-Velocity. So, for one of their high altitude missions, the X-15 was airlifted to 45000 ft @ 790 ft/s. The rocket ignited and it accelerated for 84.5 seconds until burn out where it was travelling at 5380 ft/s @ 176000 ft. The aircraft continued to climb until it reached ~360000 ft @ 4150 ft/s, and then it began a reentry phase.

 

SO...

Knowing this, we would like to remove test equipment and add people. We're looking at a max of ~400 lbs addition. Am I wrong in thinking that we would still be able to achieve 360000 ft using the same engine, despite the additional losses due to overcoming increased gravity (weight)? We're going to look at thrust required vs thrust available due to mach divergence at M=1, but I'm still figuring we have far more power than needed.

 

• Part of me says well with 60000 lbs of thrust going 100% throttle for the full burn, they reached 360000 ft. Adding more weight will result in less performance. Reducing thrust will result in less performance.
• Another part of me says well... we are outside of useable atmosphere (no stall now), so why the hell do we feel the need to go 4150 ft/s at apogee? Instead of wasting fuel towards massive acceleration, can we reduce the throttle (decrease mass flow rate), extend burn time, go slower but reach the same or higher altitude?

 

I think this all depends on the trajectory that you wish to achieve - as I recall the X15 accelerated to that speed and then followed a ballistic trajectory to the apogee altitude.  Also, if you want to achieve orbit you'll need a LOT more speed than that!  Earth's escape velocity is over 7km/s   It's counter-intuitive, but I'm pretty sure that if you want to reach that altitude with the same trajectory and slower speed it will take a lot more fuel.

 

I assume that you already have references like these, but here's a couple that might be helpful:

http://en.wikipedia.org/wiki/Escape_velocity

http://en.wikipedia.org/wiki/Sub-orbital_spaceflight

 

Also, have you seen the Steam game called Kerbal Space Program?

 

That's a cool project, btw.  

Edited November 19, 2014 by TimZ

[Tony D]

1.62 km/sec isn't even close...

But it is "Superman fast" as speeding bullets aren't that speedy (SR71 shot itself as it ran through it's own hail of bullets!

 

"X-15, the Original Mach-5"!

[BLOZ UP]

Also, have you seen the Steam game called Kerbal Space Program?

 

 

I've got 200+ hrs in that game. And many lost Kerbals.... RIP in peace.

 

That game has done more to educate me in 'space is hard' than any book.

 

Relevant XKCDs:

 

 

 

[TimZ]

I've got 200+ hrs in that game. And many lost Kerbals.... RIP in peace.

 

That game has done more to educate me in 'space is hard' than any book.

 

 Yep!  I'm officially addicted.

[josh817]

I've got 200+ hrs in that game. And many lost Kerbals.... RIP in peace.

 

That game has done more to educate me in 'space is hard' than any book.

 Yep!  I'm officially addicted.

 

I do in fact have that game, though I haven't played it in a while.

 

This question is similar to saying:

I travel from point A to point B going 90MPH, flooring it at every green light to get back up to speed, and use 10 gallons of fuel. If I reduce my speed and drive calmly, will I get from A to B with less fuel. This seems obvious, yes. What about when I add weight (greater effect on aircraft of course)?

 

What I'm trying to do is NOT reinvent the wheel. 360000 ft is already sub orbital. Now we have to accomodate 2-4 passengers. I pose the question of logic in an attempt to keep the same engine, same flight path, etc. The orbital requirements will call for more extreme modifications and depending on the orbit parameters will dictate the deltaV required, which is easy to calculate.

 

I think where I'm getting off track is that being a ballistics problem, the aircraft will have a vertical and horizontal vector and although it is going 4150 ft/s, its vertical velocity is 0 ft/s, I would think...

 

Perhaps I just answered my own question... Being in "space" with no aerodynamic forces, even if you pitched the aircraft nose down (it had RCS), you would continue to climb until your vertical velocity is 0 ft/s, upon which you would fall back to Earth.

 

 

 

So I guess lets just talk about Kerbal Space Program now............. I have a satellite geosynchronous orbit, a refueling space station in LEO, and a whole bunch of debris/kerbal dudes floating around which I don't have the patience to save.

 

 

1.62 km/sec isn't even close...

But it is "Superman fast" as speeding bullets aren't that speedy (SR71 shot itself as it ran through it's own hail of bullets!

 

"X-15, the Original Mach-5"!

 

Oh and Tony, max speed was Mach 6.7 but the aircraft started melting. There was a more powerful rocket in developement when the program was shutdown after the death of a pilot.

Edited November 19, 2014 by josh817

[BLOZ UP]

In the desired circular orbit, vertical speed is zero.

 

It doesn't matter what the horizontal velocity was at max altitude if the vertical is zero, and you're out of fuel (and atmosphere).

 

Since we're suborbital, what you can do to reach the same height is alter the trajectory. Do the people have to survive re-entry?

Edited November 19, 2014 by BLOZ UP

[josh817]

The orbital mission will be reviewed next semester; the parameters of said orbit have yet to be discussed as far as altitude and ecentricity. For now we only care about suborbital.

 

After contemplating the vector thing, the trajectory seems to be the answer. Convert this thrust into more potential energy (altitude) rather than kinetic energy. We will have to see the loading on the aircraft during a pull up maneuver to higher climb angles.

 

And yes, everyone must survive... My group is only worried about going up though, not coming back down. That's the aerodynamics problem.

[BLOZ UP]

So your team is going to demo this in KSP, right? You should fire it up again, 0.25 added a bunch of features.

 

Any of you guys make a space plane (SSTO) that can actually take anything worthwhile into orbit? I've got rockets down well my my space planes all have fuel issues getting back.

[TimZ]

Any of you guys make a space plane (SSTO) that can actually take anything worthwhile into orbit? I've got rockets down well my my space planes all have fuel issues getting back.

I thought you'd never ask...

 

Here's my latest personnel transport.  I used it to populate a base that was going to go to Eve.

2 crew plus 12 passengers

 

Took off from KSC, achieved a 130km circular orbit, rendezvoused and docked with the Eve base craft, transferred crew and passengers, flew back to KSC and landed on runway using remote guidance.  Yes I'm a nerd.

 

Edited November 20, 2014 by TimZ

[BLOZ UP]

Interesting. Do you have any mods? I have Kerbal Engineer/B9/KW/Chatterer ... and one of the robotics ones, can't remember the name. What's your T/O Weight?

 

I'm trying to make one of the large cargo planes into a SSTO to carry a huge rover, but ended up needing boosters. Well, I guess technically it's still just a single stage since all engines activate at once...

 

Otherwise I just try to make ridiculous stuff all Howard Hughes style.

Edited November 20, 2014 by BLOZ UP

[TimZ]

So far this was all stock.  Not even MechJeb.

Interesting. Do you have any mods? I have Kerbal Engineer/B9/KW/Chatterer ... and one of the robotics ones, can't remember the name. What's your T/O Weight?

 

I'm trying to make one of the large cargo planes into a SSTO to carry a huge rover, but ended up needing boosters. Well, I guess technically it's still just a single stage since all engines activate at once...

 

Otherwise I just try to make ridiculous stuff all Howard Hughes style.