Why do you aerospace engineers have such a hard time making spacecraft?

[gaming_addict]

Yup, high altitude only helps so you could go insanely fast without vaporizing. That tiny bit of less gravity at higher altitudes doesn't help at all.

 

[Danger]

Fred, I just thought of something else. If your exhaust is electrically active, such as a plasma, could a variable nozzle be made using a magnetorestrictive collar rather than a mechanical device?

 

[FredGarvin]

Fred, I just thought of something else. If your exhaust is electrically active, such as a plasma, could a variable nozzle be made using a magnetorestrictive collar rather than a mechanical device?

I really don't know about how well they are using magnetic shielding for ion drives. I haven't heard of them being able to control it like that. Someone else would have to answer that one for sure.

 

[gaming_addict]

Fred, I just thought of something else. If your exhaust is electrically active, such as a plasma, could a variable nozzle be made using a magnetorestrictive collar rather than a mechanical device?

Magnetorestrictive equipment could be heavy. Although, it gives me an idea to separate the plasma into positive and negative ions using a plain magnetic field.. it could probably give very high voltages. I would route the negatively charged electric field to the wing leading edge, the whole frontal area and the upper part of lifting surfaces to eliminate or reduce shockwaves, and hence, drag.

On a second thought.. On LH-fueled scramjets, highspeed of plasma could bring about strong internal magnetic fields, ion separation could occur with no certain pattern. A small amount of rotation could be introduced to the plasma flow such as a slightly helical exhaust pipe design or spiral 'riflings'. The slight rotation of the plasma exhaust would bring the heavier positive ions to the walls of the combustion chamber and the negative ions to the center.

The positively charged combustion chamber could then be used to charge an interior metallic plating in front of the vehicle to high positive voltage, so external plate(acting like a capacitor) attracts negative ions from air and gets negatively charged. The negatively charged plating would then help to reduce shockwaves and shockwave drag.

 

[laurelelizabeth]

I'm not, but I consider that error a compliment.
Your second post needs clarification. What if they made what at a higher altitude?

haha... i just thought that would sound clever to say ... it is a compliment

About the second post (oopsie, did i double post?) I was just thinking that if they made the spacecraft 's at a higher altitude then theoretically there would be less gravity... Although I'm assuming it wouldn't make a difference.

 

[Astronuc]

I'm familiar with the cost of LOX, it's cheap but carrying the weight of LOX will incur a larger amount of fuel burned. The air in the atmosphere is free and doesn't need to be carried around for scramjet.

Yep. Much of the work that surface launch rockets do is lifting the propellent.

See this page - http://www.braeunig.us/space/specs/shuttle.htm

EXTERNAL TANK
Length: 46.88 m
Diameter: 8.40 m
Dry mass: 35,430 kg for earlier version, later reduced to 29,930 kg in later models, 26,330 kg for aluminum-lithium alloy Super LightWeight version
Oxidizer: liquid oxygen
Fuel: liquid hydrogen
Propellant mass: about 730,000 kg
Pressurization: 3.0 atm LH2, 1.43 atm LOX
Feed lines: supplies SSMEs through two 43.2 cm diameter outlets
Insulation: 25 mm-thick polyurethane foam
Separation: after about 530 s, 110 km altitude, for destructive reentry

SOLID ROCKET BOOSTERS
Length: 45.46 m (including forward skirt and nose fairing)
Diameter: 3.71 m
Empty mass: each 82,879 kg
Propellant: TB-H1148 HB Polymer
Propellant mass: each about 504,000 kg
Thrust: combined thrust 29.36 MN SL (maximum thrust at launch reducing by 1/3 after 50 s)
Burn time: about 124 s
Steering: nozzle gimbaled +/-8o by two hydraulic actuators
Separation: after burnout at about 124 s, 45 km altitude (triggered when pressure falls to 3.4 atm), the boosters are separated pyrotechnically and fall into the Atlantic for recovery. Landing speed <100 km/h under 3 x 41 m diameter parachutes
Separation motors: 16 flown per Shuttle mission; each 73 kg mass, 34.5 kg HTPB propellant, 0.8 s burn time, 82.6/129.5 kN vac avg/max thrust, 78.1 kNs total impulse

The solid rocket boosters are there to get the EXTERNAL TANK to fly with the Shuttle. The ET is feeding the Shuttle.

NASA's Space Shuttle includes a reusable manned spacecraft capable of delivering up to 25,000 kg of cargo into low Earth orbit.