Suborbital flight durations

Status
Not open for further replies.
D

dreada5

Guest
Hi guys<br /><br />I have a question about suborbital flight; with the assumption that tourist flights will catch on within the next few years and that customers will request longer and longer space experiences. <br /><br />Obviously one of the reasons that suborbital is easier than orbital is that no re-entry heating is involved - but can suborbital flight duration be increased by flying further out into space and reserving some fuel for an engine re-start during descent to slow atmosphere re-entry speed, minimising resultant heating? Is that feasible?
 
U

usn_skwerl

Guest
If you fly straight up instead of ~65 miles out to 100 miles, I don't think additional heat shield is necessary. Depending on how fast they are, if in an arc, and the ballistic trajectory, at least some TPS is necessary. <br /><br />Someone else can give a much better explanation, I think. <div class="Discussion_UserSignature"> </div>
 
D

docm

Guest
Space Review posted about SS1;<br /><br /><blockquote><font class="small">In reply to:</font><hr /><p>The heating on the spacecraft is also limited during reentry—the stagnation temperature at peak heating is just under 600°C—meaning the spacecraft needs only a limited thermal protection system (TPS). “We have designed the structure so that the crew is not in jeopardy if the TPS fails,†Rutan said, although he added that the vehicle would require repairs if the TPS failed.<p><hr /></p></p></blockquote><br />600 C = 1,112 F, just under the melting point of Aluminum (660 C/1,220 F). <br /><br />Wikipedia has a nice article on atmospheric reentry here.... <div class="Discussion_UserSignature"> </div>
 
H

holmec

Guest
<blockquote><font class="small">In reply to:</font><hr /><p>Obviously one of the reasons that suborbital is easier than orbital is that no re-entry heating is involved - but can suborbital flight duration be increased by flying further out into space and reserving some fuel for an engine re-start during descent to slow atmosphere re-entry speed, minimising resultant heating? Is that feasible?<p><hr /></p></p></blockquote><br /><br />There is reentry heating involved in suborbital reentry.<br /><br />SpaceShipOne was made of carbon composite which is heat resistant. Beyond that I don't know if they took any other precautions as far as a heat sheild.<br /><br />SpaceShipOne did have a way to measure the heat with some wax strips on the nose and leading edge of wings.<br /><br />If you want to use thrusters on reentry, you have to take into account the extra fuel. Normally only enough fuel to get up to suborbital is taken along. If you make calcs on a spreadsheet you may find that its very expensive to take one extra fuel. <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>
 
T

thereiwas

Guest
SS1 did have some additional thermal protection on the leading edges. You can see it as some pink stuff that is present only in the flights going to space. This was not just for protection on the way down, but on the way up as well. Heating loads were about the same.
 
W

webtaz99

Guest
I believe Burt Rutan has alluded to this (reentry) as one of the "nuts to crack" in developing orbital flights. I have a funny feeling he's going to whip out something as innovative as the feather. The bummer is, we won't see it till it flies. <div class="Discussion_UserSignature"> </div>
 
D

docm

Guest
Agreed. If someone's going to come up with an outside-the-box re-entry innovation it'll be Rutan. <div class="Discussion_UserSignature"> </div>
 
P

PistolPete

Guest
What goes up must come down, and the amount of energy that you expend to get up will have to be dissipated on the way down. The more energy you expend to get up the more you will have to dissipate on the way down.<br /><br />In theory, there is nothing that prevents the Space Shuttle from going straight up and doing a suborbital hop. Well, there may be one thing. The Shuttle dissipates its energy by reentering the atmosphere at an angle and slowly releasing it over time. If the Shuttle came in straight down, then the energy would be be dissipated through the thickest part of the atmosphere, possibly overloading the heat shield. So I suppose that there is an upper practical limit on how big a suborbital hop can be. <div class="Discussion_UserSignature"> <p> </p><p><em>So, again we are defeated. This victory belongs to the farmers, not us.</em></p><p><strong>-Kambei Shimada from the movie Seven Samurai</strong></p> </div>
 
H

holmec

Guest
<blockquote><font class="small">In reply to:</font><hr /><p>This was not just for protection on the way down, but on the way up as well. Heating loads were about the same.<p><hr /></p></p></blockquote><br /><br />This doesn't make sense. On the way up your accelerating in a denser atmosphere to a less dense atmosphere. So heating is not as much of a factor since viscosity is less of a factor. On reentry your accerating in a near vacuum into more dense atmosphere which creates a lot of viscosity.<br /><br /> <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>
 
N

nimbus

Guest
(I'm responding to the re-entry discussion in general, not you specificaly, Holmec)<br />Why hasn't aerocapture/airbraking been tried yet with the Earth's atmosphere? Isn't it the simplest (cheapest) and most natural re-entry method? <div class="Discussion_UserSignature"> </div>
 
M

MeteorWayne

Guest
It's fine for suborbital.<br /><br />Orbital, and interplanetary speeds are much harder to damp out in a reasonable time period.<br /><br />Recall Mars aerobraking took many months, with a small mass.<br /><br />Not so good for the STS Orbiter. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>
 
T

thereiwas

Guest
You can do it in one pass if you have a big enough cross section. The only way to do that is with an inflatable aeroshell to considerably increase the cross sectional area. So far experiments with this technology have been less than spectacular. But then a lot of money has not been thrown at it either.<br /><br />I think inflatable hypersonic aeroshells are a key technology for both Mars and Earth landings. The numbers I've been developing over in the "Mars 9 tons at a time" thread are very promising, if the engineering can be worked out.
 
H

holmec

Guest
Really, All reentry spacecraft have been using the atmosphere to brake. Otherwise rockets would have been needed and more expense.<br /><br />This is the purpose of the heat sheild anyway. Its because of using the atmosphere to break that spacecraft need heat sheilds.<br /><br />But if you maximize your areobraking ability, you might crush your crew with outrageous Gs. The key is to find the right amount of aerobraking with the right speed taking into account the differential pressure in the atmosphere as the craft descends. <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>
 
A

ace5

Guest
Anyone has updated drawings of the redesigned Rocketplane XP?<br />Its gorgeous.
 
D

dreada5

Guest
Thanks holmec.<br /><br /><blockquote><font class="small">In reply to:</font><hr /><p>If you want to use thrusters on reentry, you have to take into account the extra fuel. Normally only enough fuel to get up to suborbital is taken along. If you make calcs on a spreadsheet you may find that its very expensive to take one extra fuel. <p><hr /></p></p></blockquote><br /><br />I obviously haven't done the calcs but I was thinking as current suborbital proposals IMO offer fleetingly short experiences:<br /><br />If it were possible to add something like another 10+ mins onto a suborbital/weightless experience, then that may be something that tourist will highly value enough to pay higher fees for carrying the extra re-entry fuel, rather than wait 5-10 more development years for commerical orbital flights with shuttle-like TPS??
 
H

holmec

Guest
Theoretically you can launch go as high as you want. Its the reentry that will be the hard.<br /><br />Other than a rocket thruster, there are other ways to consider:<br /><br />1. Atmopheric bouyancy: Could a balloon assist on reentry?<br /><br />2. Really large area for viscosity. Could design for a variable area so to control the Gs inside the craft. Less dense atmosphere needs more area to provide the same viscosity as a smaller area in a more dense atmosphere.<br /><br />3. Heat deflection: Is there a better way to deflect the heat other than material burning? How about not using a smooth skin?<br /><br />In any case the main thing you want to think about on reentry is weight to lift ratio. And by lift, we mean air resistance.<br /><br />What about using the energy on reentry to slow down the craft? Or use it to power an electro magnetic field to protect the craft.<br /><br />Really there are a lot of ideas to reenter the atmosphere. And you can try to combine ideas. NASA has done it two ways, the Apollo blunt surface reentry, and the Shuttle controlled angle reentry.<br /><br />If you want to use rockets, you may consider using solid fuel. They store for long periods of time, and they burn predictably for a set amount of time. <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>
 
Q

qso1

Guest
It is apparently not the cheapest way to re-enter earths atmosphere. The current method is easiest and cheapest and since dollars run our space efforts, aerobraking will not likely come onto the scene unless or untill its cost advantages clearly outweigh conventional re-entry methods. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>
 
H

holmec

Guest
<blockquote><font class="small">In reply to:</font><hr /><p>untill its cost advantages clearly outweigh conventional re-entry methods.<p><hr /></p></p></blockquote><br /><br />I would think a manned aerobraking craft would need some pretty heafty design characteristics. <br /><br />Aerobraking has been used with non manned craft for a period of months. And small amounts of air pressure were exerted on the craft.<br /><br />But a manned craft may want to delve deeper in the atmosphere to get sufficient pressure to break faster. On the downside that might involve going through the ionosphere several times. <br /><br />I guess that such a craft would need a large drag area. I envisioned a capsuled craft using an apparatus similar to a parachute but that uses pneumatics for rigidity. That is inflatable. That is could be used for some aerobraking passes and then discarded for reentry. <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>
 
Q

qso1

Guest
Aerobraking for a manned Orbital Transfer Vehicle (OTV) was studied extensivelly during the mid to late 1980s. Then the budget ax fell on OTV enough to make it unmanned and referred to as an OMV, M for maneuvering. By 1991, even that was deemed unaffordable.<br /><br />The aerobrake envisioned in those studies was not unlike a larg turtle shell designed to enshroud a portion of the OTV or OMV providing re-entry protection. As our return to Orion manned space capsules demonstrates, we (public, Politicians) are not willing to budget much beyond that. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>
 
H

holmec

Guest
<blockquote><font class="small">In reply to:</font><hr /><p>The aerobrake envisioned in those studies was not unlike a larg turtle shell designed to enshroud a portion of the OTV or OMV providing re-entry protection. As our return to Orion manned space capsules demonstrates, we (public, Politicians) are not willing to budget much beyond that.<p><hr /></p></p></blockquote><br /><br />I do think there is still value in the study. Maybe some company would endeavor to use the data to make a reusable space craft. <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>
 
Status
Not open for further replies.

Latest posts