Re: How Rockets Differ From Jets

in article 1130234085.894290.193300@xxxxxxxxxxxxxxxxxxxxxxxxxxxx, tomcat at
jlavine@xxxxxxxxxxxxx wrote on 10/25/05 2:54 AM:

> George Evans wrote:
>
>> Unless your craft weighs more than one million lbs full throttle will likely
>> kill everyone on board.
>>
> Rocket sled experiments proved that the body can take upward to 40 G's. A 4:1
> thrust to weight ratio shouldn't exceed about 10 G's. This ratio would only
> exist at the end of the fuel supply and then only for a half minute or so.

Here is a little physics lesson. A thrust to weight ratio is equal to the
g's. A burn at a ratio of 4:1 will cause 4 g's of acceleration. Rocket sled
tests showed that a person will sustain injuries at 40 g's and that is with
a very brief exposure not a long burn.

> The initial thrust to weight ratio would be 1:1 or, perhaps, a little less. A
> spaceplane is a 'flying gas can'. As the fuel is used the thrust to weight
> ratio increases rapidly. A 6 minute supply of fuel means only 6 minutes of
> increased G force.
>
> Taking a spaceplane into orbit should require a 4 minute burn at most. During
> this burn peak G's should not exceed 5 or 6.
>
> At takeoff the GLOW (Gross Lift Off Weight) should be around 6 million pounds.
> A F-15 Eagle has about a 1:1 thrust to weight. So, we are talking about a
> fighter jet kind of force at takeoff.

You better forget about passengers.

George Evans


.

Relevant Pages