Earth re-entry problems

RE: Earth re-entry problems

“ahh it was just a thought garry…….
as for fuel, why not have it stored on the ISS??”

There is some fuel stored on the ISS but it is used to maintain orbit.

If you wanted to use fuel stored on the ISS to fuel a landing you would be in the unusual situation of flying 20-30 times more often into space for the sole purpose of making every 50th or 60th flight a little safer… and that is only in theory. Most of the accidents that have occured in the short life of space rocketry have involved liftoff for the very simle reason that a rocket is a controlled explosion. I don’t know that doing that more often would make it safer.

I personally think that until some new and far more efficient propulsion system can be designed the best solution would be to have several layers of heat tiles so that even if one entire layer was lost there would still be plenty of protection for the aircraft.
Of course that would eat into payload capacity and my solution there would be to remove the main rockets of the shuttle and get rid of the solid rocket boosters and use a more powerful but disposable rocket to launch the spaceshuttle. (Like Buran)

“ahh it was just a thought garry…….”

Not burning you on a cross 🙂 Just pointing out that although it could be made to work it would be very inefficient and not necessarily safer.

“So when are europeans going to send a shuttle in orbit?.. “

Buran was launched quite some time ago…

Seriously though i think the Japanese will be the next (country) to launch a space shuttle.

RE: Earth re-entry problems

>a new design sounds sensible… BUT… it’s built by Boeing,
>which can mean only one thing…
>
>stand by for the Space Shuttle NG…
>
>the almost newly designed, Orbiter-600 (also avaliable in
>slightly bigger -7/8/900 series).
>
>Combining the best 30 year old technology with slightly
>bigger luggage racks.
>
>Plus, of course (and this is best bit) the option of
>winglets.
>
>and of course, the loosely based upon BBO (Boeing Business
>Orbiter).

So when are europeans going to send a shuttle in orbit?..

A-54XX?

RE: Earth re-entry problems

ahh it was just a thought garry…….

as for fuel, why not have it stored on the ISS??

coanda

RE: Earth re-entry problems

“what about this, you stop the orbiter where you want it to be, you make it STILL in space. then you allow the orbiter, using a little persuasion perhaps, to fall into the atmosphere, which for all intents and purposes is also NOT moving. if you do this at a big enough number of orbital rotations away from where you want to land you could quite plausibly fall under some rocket braking initially and then via para foil or parachute to the landing zone. the time this would take prob wouldnt be great enough for the earth to advance through its own orbit around the sun to make any real differnce.”

Where to start…

OK, first of all the ONLY reason things stay in orbit of Earth (or any large body) is because they are travelling at orbital speed. If you reduce that speed it will start to fall… the more you reduce it the faster its downward trajectory. (BTW if you increase the speed it will escape earths pull and fly off into free space… necessary to go to the moon or other planets).
To reduce the Spaceshuttles speed relative to a point on the surface of the Earth to zero would require roughly the same amount of energy that was needed to get it up to that speed in the first place. (in fact it would be marginally less because when it was speeding up it had to fight friction in the atmosphere as well which was working against it… and it will also help to slow the shuttle on the way down too, also reducing the energy force required to slow down (note currently only atmosphereic drag is used to stop the shuttle so it is quite a powerful force.).
This means to stop the shuttle still in space above the Earth you need that large tank fixed to the shuttle at takeoff full of fuel plus the two solid rocket boosters full as well. This is beyond the payload capacity of the shuttle (ie it can’t carry two main tanks and four solid rocket boosters into space if it can only use one tank and two rocket boosters.

Currently a small amount of rocket fuel is used to slow the shuttle down to below orbital speed and aerodynamic braking does the rest.
I can’t think of a more efficient way to do it… except entering the realms of science fiction.

“the time this would take prob wouldnt be great enough for the earth to advance through its own orbit around the sun to make any real differnce.”

If you are travelling at oribtal speed or less than orbital speed then the earth moving away from you around the sun will not be a problem. If you don’t exceed orbital speed then you are not travelling fast enough to leave the Earth… it won’t leave you either… it will just drag you along with it.

RE: Earth re-entry problems

a new design sounds sensible… BUT… it’s built by Boeing, which can mean only one thing…

stand by for the Space Shuttle NG…

the almost newly designed, Orbiter-600 (also avaliable in slightly bigger -7/8/900 series).

Combining the best 30 year old technology with slightly bigger luggage racks.

Plus, of course (and this is best bit) the option of winglets.

and of course, the loosely based upon BBO (Boeing Business Orbiter).

RE: Earth re-entry problems

Currently the only way to slow the shuttle down is to use the Earths atmosphere. It does what is called a de-orbit burn to start its decent into our atmosphere, but after that it has no or very little fuel left so it uses friction on the air to slow down.

Becasue to go from 12,500mph to 100mph or so in less than 3,000 miles is some feat to do.

I do belive it is time for a new shuttle designed, perhaps a more areo-dynamic one and come in at a slightly slower speed, this could be faciltated by a longer de orbit burn. With a shuttle redesign this should be possible. The other option would to have a space configuration and a earth configuration so it can manover rather than gliding.

Nikumba

RE: Earth re-entry problems

re-entry speed will always be an issue and cost cutters will always want the least fatigue on the airframe, so that it can carry out the maximum number of missions before it becomes a danger to fly.

Garry, in your post, after mine, you have said the same thing as me. you can come through quicker, at a steeper angle or you can go through slower at less of an angle.

what about this, you stop the orbiter where you want it to be, you make it STILL in space. then you allow the orbiter, using a little persuasion perhaps, to fall into the atmosphere, which for all intents and purposes is also NOT moving. if you do this at a big enough number of orbital rotations away from where you want to land you could quite plausibly fall under some rocket braking initially and then via para foil or parachute to the landing zone. the time this would take prob wouldnt be great enough for the earth to advance through its own orbit around the sun to make any real differnce.

just a thought………..

coanda

RE: Earth re-entry problems

The problems overcoming our atmosphere as well as Earths large gravity is what makes a moonbase so appealing.

If we built a permanant base on the moon we could mine minerals (admittedly the Moon is rather metal deficient) and sent them out into space very cheaply. With less gravity and no atmosphere you could launch things into moon orbit or out into deeper space simply by placing a set of coils along the surface long enough to accelerate an object to the moons escape velocity (off the top of my head I think it is about 2km/s which is much lower than the Earths 11km/s EV.
Also without an atmosphere it doesn’t need to go straight up… it just has to point at sky… even on the horizon. (a mountain in the way would of course be a problem.)

RE: Earth re-entry problems

Hmm, I understand the point that each of you makes. My point was not to ask whether a vertical descent was superior to the current method – any twit would realise that it isn’t. Garry has gone closest to the problem that currently exists. Slower entry can only come about by some form of braking, as I mentioned, and the only form which is currently effective is by reverse thrust through rockets. But these require huge amounts of fuel, restricting payload etc…

So far, nobody has come up with any alternatives to current technology and I certainly don’t have any answers either. That was the point of my post – looking for ideas on how to address this problem. For example, what sort of speed could the shuttle reduce to and still hold its approach pattern, without “stalling” or losing momentum and entering an excessively vertical descent?

One thing that must be looked at is the current heat shield of ceramic tiles. They could be the major weak link in the whole re-entry process. If no existing metal can survive the levels of friction during re-entry, some other form of heat protection, which is more durable and less susceptible to damage from external contact than the tiles, needs to be devised. If such a durable heat shield could be developed, the re-entry speed might not be an issue.

Regards

Wombat

RE: Earth re-entry problems

[updated:LAST EDITED ON 04-02-03 AT 05:31 AM (GMT)]can’t stop !! shuttle descent is a parabola… as well as take off.. once you get going you have orbital velocity and you have to get back the same way..

RE: Earth re-entry problems

“There is NO easier way to get through the atmosphere it just has to be done this way, you either go through very quickly with very high temps or you go through slowly with lower temps, either way you’ll have the same problems of heating.”

Actually the options are either go through the atmosphere fast and hot with a payload capacity, or use more energy to slow down to deorbit, come in a quite a bit cooler, but have no room on board for payload (the extra braking must come from somewhere and in space it can only practically come from a rocket engine and lots more fuel.

The angle of reentry was calculated specifically to prevent 2 things.
The first is if the angle is too shallow the spacecraft will just skip across off the atmosphere out into space again.
The second is if it is too steep the spacecraft will come in too fast, overheat and burn up (irrespective of the heat shields).
The currently used trajectories are the best compromise in dumping speed when coming out of orbit.
This is the First problem NASA has had with reentry, and it was probably because of damage on launch rather than flawed procedures or systems.

RE: Earth re-entry problems

yeah, stop in mid space and drop vertically to the ground, in controlled descent, this would work!

asfar as the control fothe columbia goes, it was as far as I am aware fully automated and the autopilot itself holds its own ‘chinese parliament’ with all teh data it collects and acts to adjust the aircraft so that it remains within the limits its set.

in this case the autopilot WAS trying to correct the extra drag problem, it couldnt do it quick enough or with enough deflection, and perhaps it isnt given enough options. autopilots dont get much better than this to be honest. all but one re entry with the shuttle as I understand has been carried out under autopilot (one USMC guy flew a re entry once.)

There is NO easier way to get through the atmosphere it just has to be done this way, you either go through very quickly with very high temps or you go through slowly with lower temps, either way you’ll have the same problems of heating.

TOO MANY VARIABLES

coanda

RE: Earth re-entry problems

Well, the fact is that when in orbit you have to go fast (in order to maintain altitude). If you reduce yor tangential speed, you will have a bigger vertical speed, which will produce friction problems in a descent too.
So the friction problems appears to be unavoidable for me, unless a way of eliminating the air in front of the vehicle is developed, but this sound as a sci-fi story.